1. No category

Characterization of timing jitter spectra in freerunning mode-locked lasers with 340 dB dynamic
range over 10 decades of Fourier frequency
Kwangyun Jung and Jungwon Kim*
School of Mechanical, Aerospace and Systems Engineering, Korea Advanced Institute of Science and Technology (KAIST),
Daejeon 305-701, Korea
*Corresponding author: jungwon.kim@kaist.ac.kr
Received Month X, XXXX; revised Month X, XXXX; accepted Month X,
XXXX; posted Month X, XXXX (Doc. ID XXXXX); published Month X, XXXX
We demonstrate a method that enables accurate timing jitter spectral density characterization of free-running mode-locked
laser oscillators over more than 10-decade of Fourier frequency from mHz to tens MHz range. The method is based on
analyzing both the input voltage noise to the slave laser and the output voltage noise from the balanced optical crosscorrelator (BOC), when two mode-locked lasers are synchronized in repetition rate by the BOC. As a demonstration
experiment, timing jitter spectrum of a free-running mode-locked Er-fiber laser with a dynamic range of >340 dB is
measured over Fourier frequency ranging from 1 mHz to 38.5 MHz (Nyquist frequency). The demonstrated method can
resolve different noise mechanisms that cause specific jitter characteristics in free-running mode-locked laser oscillators for a
vast range of time scales from <100-ns to >1000-s.
OCIS Codes: (320.7090) Ultrafast lasers; (270.2500) Fluctuations, relaxations, and noise; (320.7100) Ultrafast
measurements; (120.3940) Metrology.
Spectral purity of electronic and photonic oscillators is
important for advancing various scientific and
engineering applications such as high-precision
synchronization [1], high-speed and high-resolution
sampling and analog-to-digital converters [2], timing,
time-keeping and navigation systems, clock distribution
and communication networking equipment, signal
measurement instrumentation, and radars and lidars, to
name a few. For the optimization of oscillator
performances, accurate characterization of phase noise
and timing jitter of periodic signals generated from the
oscillators is first required.
Recently it has been identified that femtosecond modelocked lasers can serve as ultralow-noise photonic and
electronic oscillators: mode-locked lasers can generate
both optical pulse trains with extremely low timing jitter
and, via proper optical-electronic (O-E) conversion process,
microwave signals with extremely low phase noise.
Recent measurements showed that free-running,
passively mode-locked fiber lasers can generate both
~100-MHz repetition rate optical pulse trains and 10-GHz
microwave signals with integrated timing jitter well below
a femtosecond (when integrated from 10 kHz to >10 MHz
Fourier frequency) [3-5].
Due to the intrinsically low level of timing jitter (e.g.,
lower than 10-4 fs2/Hz at 10 kHz Fourier frequency [3,4])
and the equivalent phase noise (e.g., <-140 dBc/Hz at 10
kHz Fourier frequency for 10-GHz carrier [5]), the
accurate measurement of timing jitter spectral density in
mode-locked laser oscillators has been a challenge.
Traditionally, the timing jitter of optical pulse trains was
measured in an indirect way by characterizing the phase
noise of microwave signals converted from the optical
pulse trains via O-E conversion (typically, using fast
(>GHz) photodetectors) [6]. After a bandpass filtering of
one harmonic frequency component, the microwave signal
is mixed in quadrature with low-noise electronic tracking
oscillator, which can be performed by several
commercially available signal source analyzers (such as
[7]). Although this photodetection-based method is a
simple method that can utilize microwave components
and commercial instruments, its measurement dynamic
range and resolution are insufficient for accurate
characterization of mode-locked lasers. First, the
measurement dynamic range and resolution are often
limit by the shot noise and thermal noise in the
photodetectors, which results in a typical measurement
noise floor of ~ -140 to -150 dBc/Hz. In addition, the excess
phase noise by amplitude-to-phase (AM-to-PM)
conversion in the photodetection and microwave
amplification can add unwanted timing jitter/phase noise,
which is not part of real laser noise. This excess noise can
be problematic for the accurate characterization of jitter in
the low Fourier frequency when the laser is locked to a
stable reference source.
As an alternative, the use of balanced optical crosscorrelation (BOC) has recently enabled tens of attoseconds
resolution characterization of the high-frequency timing
jitter spectral density in mode-locked lasers up to the full
Nyquist frequency [3,4,8]. The BOC-based timing detector
method requires a low-bandwidth phase-locked loop
(PLL), which uses two almost identical mode-locked lasers
and locks the repetition rates of two lasers using a
piezoelectric transducer (PZT)-mounted mirror driven by
the output signal from the BOC via a proportionalintegral (PI) servo controller. Due to the nonlinear optic
arXiv:1412.0161v1 [astro-ph.IM] 29 Nov 2014
Background optimization for a new spherical gas
detector for very light WIMP detection
Ali Dastgheibi-Fard∗a , I. Giomatarisb , G. Gerbierb , J. Derréb , M. Grosb , P. Magnierb ,
D. Jourdeb , E .Bougamontb , X-F. Navickb , T. Papaevangeloub , J. Galanb , G.
Tsiledakisb , F. Piquemalc , M. Zampaoloc , P. Loaizac , I. Savvidisd . Saclay and LSM
teams of - New Experiments With Sphere - network
a LSM,
Carré Sciences, 73500 Modane and CEA Saclay - IRFU/SEDI - 91191 Gif s Yvette
Saclay - IRFU/SEDI - 91191 Gif s Yvette
Carré Sciences, 73500 Modane
d Aristotle University of Thessaloniki, Greece
b CEA
c LSM,
E-mail: ali.dastgheibi-fard@lsm.in2p3.fr
The Spherical gaseous detector (or Spherical Proportional Counter, SPC) is a novel type of particle detector, with a broad range of applications. Its main features include a very low energy
threshold independent of the volume (due to its very low capacitance), a good energy resolution,
robustness and a single detection readout channel, in its simplest version. Applications range
from radon emanation gas monitoring, neutron flux and gamma counting and spectroscopy to
dark matter searches, in particular low mass WIMP’s and coherent neutrino scattering measurement. Laboratories interested in these various applications share expertise within the NEWS
(New Experiments With Sphere) network. SEDINE, a low background prototype installed at
underground site of Laboratoire Souterrain de Modane is currently being operated and aims at
measuring events at very low energy threshold, around 100 eV. We will present the energy calibration with 37 Ar, the surface background reduction, the measurement of detector background at
sub-keV energies, and show anticipated sensitivities for light dark matter search.
Technology and Instrumentation in Particle Physics 2014,
2-6 June, 2014
Amsterdam, the Netherlands
∗ Speaker.
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
http://pos.sissa.it/
Ali Dastgheibi-Fard
Spherical Proportional Counter
1. Introduction
There is an increasing interest for low-background, low-energy threshold detectors to identify
the dark matter in our universe and to study low-energy neutrino physics. The question of dark
matter has indeed become essential to particle physics [1]. The search for WIMP (Weakly Interacting Massive Particles) dark matter is under intense development and relies on the detection of
low energy recoils (keV scale) produced by the elastic interaction of WIMPS’s with the nucleus of
the detector. Increasing the sensitivity level requires detector scalable in target mass to 1 ton whilst
maintaining the ability to reject backgrounds. The development of such detectors remains a daunting challenge for nowadays and future low-background experiments. As for the light WIMP’s (<
10 GeV), the nuclear recoil energy (∼< keV) becomes extremely small, leading to a signal below
threshold for most conventional solid or liquid state detectors. The challenge is to achieve a very
low energy threshold, typically around 100 eV or below.
Some new experimental ideas have come to maturity. Among them is the innovative Spherical
Proportional Counter (SPC), a gaseous detector, initially proposed by I. Giomataris [3], which will
allow to explore a new region of dark matter particles of very low mass.
Radioactive background studies about the effect of the shield and radioactive contributions
from used materials are necessary to understand and optimize the detection parameters. The low
energy calibration and the reduction of the internal contamination of the inner surface of the detector and its effect on the detector background will be described below.
2. Detector description
The detector consists of a large copper sphere (from 0.6 m to 1.3 m in diameter) and a small
ball or sensor (from 3 mm to 16 mm in diameter) located at the center of the vessel,
Figure 1: Left, 60 cm spherical detector and its tube for its operation from outside of shielding; right
principle of operation of spherical gas detector
thus forming a proportional counter. The ball is maintained at the center of the sphere by a
metallic rod and is set at high voltage. The electric field varies in 1/r2 and is highly inhomogeneous
along the radius, allowing electrons to drift to the central sensor in low field regions constituting
most of the volume, while they trigger an avalanche within few mm around the sensor.
2
Nuclear halo of a 177 MeV proton beam in water
Bernard Gottschalk∗, Ethan W. Cascio†, Juliane Daartz‡ and Miles S. Wagner§
arXiv:1412.0045v1 [physics.med-ph] 28 Nov 2014
December 2, 2014
Abstract
The dose distribution of a monoenergetic pencil beam in a water tank may conveniently be
divided into a core, a halo and an aura.
The core consists of primary protons which suffer multiple Coulomb scattering (MCS) and
slow down by multiple collisions with atomic electrons (Bethe-Bloch theory). Their number
slowly decreases because of nuclear interactions, which feed the halo and aura.
The halo consists of charged secondaries, many of them protons, from elastic interactions with
H, elastic and inelastic interactions with O, and nonelastic interactions with O. By kinematic
analysis we show that the radius of the halo is roughly one third of the beam range.
The aura, extending many meters, consists of neutral secondaries (neutrons and γ-rays) and
the charged particles they set in motion.
We have measured the core/halo at 177 MeV using a test beam offset in a water tank. The
beam monitor was a plane parallel ionization chamber (IC) used as a proton counter and the
field IC a dose calibrated Exradin T1. Thus our dose measurements are absolute. We took
depth-dose scans at ten displacements from the beam axis ranging from 0 to 10 cm, adjusting
the beam current and the sensitivity of the Keithley electrometer as required. The dose spans
five orders of magnitude, and the transition from halo to aura is obvious. These data furnish
an incisive test of Monte Carlo nuclear models.
We present model-dependent (MD) and model-independent (MI) fits to these data. The MD
fit separates the dose into core (electromagnetic), elastic nuclear, nonelastic nuclear, and aura
components, and reveals roughly how much each process contributes. It has 25 parameters, and
the goodness of fit (rms (measurement/fit) - 1) is 15%. The MI fit uses cubic spline fits in depth
and radius. The goodness of fit is 9%, and this fit is more portable and conceptually simpler.
We discuss the prevalent parameterization of the core/halo, originated by Pedroni et al. [1].
Several authors have improved on the Gaussian transverse distribution of the halo dose, but all
retain (in varied notations) Pedroni’s T (w), the radial integral of the depth-dose, multiplying
both core and halo and motivating measurements with large ‘Bragg peak chambers’ (BPCs).
We argue that this use of T (w), a mass stopping power which by its definition includes
energy deposited by nuclear secondaries, is incorrect. The electromagnetic (Bethe-Bloch) mass
stopping power should be used instead. In consequence, BPC measurements and the associated
corrections are, in our opinion, irrelevant. Furthermore, using T (w) leads to spurious excess dose
on the axis of the core around midrange, which may be significant in fields involving relatively
few pencil beams.
Reference [2] is a long version of the present paper.
∗ Harvard University Laboratory for Particle Physics and Cosmology, 18 Hammond St., Cambridge, MA 02138,
USA (corresponding author, bgottsch @ fas.harvard.edu)
† Francis H. Burr Proton Therapy Center, Mass. General Hospital, 30 Fruit Street, Boston, MA, USA 02114
‡ Francis H. Burr Proton Therapy Center
§ Mevion Medical Systems Inc., 300 Foster St. Littleton, MA 01460, USA
1
1
This work has been submitted to the IEEE Nuclear Science Symposium 2014 for publication in the conference record. Copyright may be transferred without notice, after which this version may no longer be available.
arXiv:1412.0228v1 [physics.ins-det] 30 Nov 2014
Performance of a Large-Area
GEM Detector Prototype for the
Upgrade of the CMS Muon Endcap System
D. Abbaneo15 , M. Abbas15 , M. Abbrescia2 , A.A. Abdelalim8 , M. Abi Akl13 , W. Ahmed8 , W. Ahmed17 ,
P. Altieri2 , R. Aly8 , C. Asawatangtrakuldee3 , A. Ashfaq17 , P. Aspell15 , Y. Assran7 , I. Awan17 , S. Bally15 ,
Y. Ban3 , S. Banerjee19 , P. Barria5 , L. Benussi14 , V. Bhopatkar22∗ , Member, IEEE, S. Bianco14 , J. Bos15 ,
O. Bouhali13 , S. Braibant4 , S. Buontempo24 , C. Calabria2 , M. Caponero14 , C. Caputo2 , F. Cassese24 ,
A. Castaneda13 , S. Cauwenbergh16 , F.R. Cavallo4 , A. Celik9 , M. Choi31 , K. Choi31 , S. Choi29 , J. Christiansen15 ,
A. Cimmino16 , S. Colafranceschi15 , A. Colaleo2 , A. Conde Garcia15 , M.M. Dabrowski15 , G. De Lentdecker5 ,
R. De Oliveira15 , G. de Robertis2 , S. Dildick9,16 , B. Dorney15 , W. Elmetenawee8 , G. Fabrice27 , M. Ferrini14 ,
S. Ferry15 , P. Giacomelli4 , J. Gilmore9 , L. Guiducci4 , A. Gutierrez12 , R.M. Hadjiiska28 , A. Hassan8 , J. Hauser21 ,
K. Hoepfner1 , M. Hohlmann22∗ , Member, IEEE, H. Hoorani17 , Y.G. Jeng18 , T. Kamon9 , P.E. Karchin12 ,
H.S. Kim18 , S. Krutelyov9 , A. Kumar11 , J. Lee31 , T. Lenzi5 , L. Litov28 , F. Loddo2 , T. Maerschalk5 ,
G. Magazzu26 , M. Maggi2 , Y. Maghrbi13 , A. Magnani25 , N. Majumdar19 , P.K. Mal6 , K. Mandal6 ,
A. Marchioro15 , A. Marinov15 , J.A. Merlin15 , A.K. Mohanty23 , A. Mohapatra22 , S. Muhammad17 ,
S. Mukhopadhyay19 , M. Naimuddin11 , S. Nuzzo2 , E. Oliveri15 , L.M. Pant23 , P. Paolucci24 , I. Park31 ,
G. Passeggio24 , B. Pavlov28 , B. Philipps1 , M. Phipps22 , D. Piccolo14 , H. Postema15 , G. Pugliese2 , A. Puig
Baranac15 , A. Radi7 , R. Radogna2 , G. Raffone14 , S. Ramkrishna11 , A. Ranieri2 , C. Riccardi25 , A. Rodrigues15 ,
L. Ropelewski15 , S. RoyChowdhury19 , M.S. Ryu18 , G. Ryu31 , A. Safonov9 , A. Sakharov10 , S. Salva16 ,
G. Saviano14 , A. Sharma15 , Senior Member, IEEE, S.K. Swain6 , J.P. Talvitie15,20 , C. Tamma2 , A. Tatarinov9 ,
N. Turini26 , T. Tuuva20 , J. Twigger22 , M. Tytgat16 , Member, IEEE, I. Vai25 , M. van Stenis15 , R. Venditi2 ,
E. Verhagen5 , P. Verwilligen2 , P. Vitulo25 , D. Wang3 , M. Wang3 , U. Yang30 , Y. Yang5 , R. Yonamine5 ,
N. Zaganidis16 , F. Zenoni5 , A. Zhang22
Manuscript received November 30, 2014.
1 RWTH Aachen University, III Physikalisches Institut A, Aachen, Germany
2 Politecnico di Bari, Universit´
a di Bari and INFN Sezione di Bari, Bari,
Italy
3 Peking University, Beijing, China
4 University and INFN Bologna, Bologna, Italy
5 Universit´
e Libre de Bruxelles, Brussels, Belgium
6 National Institute of Science Education and Research, Bhubaneswar, India
7 Academy of Scientific Research and Technology, ENHEP, Cairo, Egypt
8 Helwan University & CTP, Cairo, Egypt
9 Texas A&M University, College Station, USA
10 Kyungpook National University, Daegu, Korea
11 University of Delhi, Delhi, India
12 Wayne State University, Detroit, USA
13 Texas A&M University at Qatar, Doha, Qatar
14 Laboratori Nazionali di Frascati - INFN, Frascati, Italy
15 CERN, Geneva, Switzerland
16 Ghent University, Dept. of Physics and Astronomy, Ghent, Belgium
17 National Center for Physics, Quaid-i-Azam University Campus, Islamabad, Pakistan
18 Chonbuk National University, Jeonju, Korea
19 Saha Institute of Nuclear Physics, Kolkata, India
20 Lappeenranta University of Technology, Lappeenranta, Finland
21 University of California, Los Angeles, USA
22 Florida Institute of Technology, Melbourne, USA
23 Bhabha Atomic Research Centre, Mumbai, India
24 INFN Napoli, Napoli, Italy
25 INFN Pavia and University of Pavia, Pavia, Italy
26 INFN Sezione di Pisa, Pisa, Italy
27 IRFU CEA-Saclay, Saclay, France
Abstract—Gas Electron Multiplier (GEM) technology is being
considered for the forward muon upgrade of the CMS experiment
in Phase 2 of the CERN LHC. Its first implementation is planned
for the GE1/1 system in the 1.5 <| η |< 2.2 region of the muon
endcap mainly to control muon level-1 trigger rates after the
second long LHC shutdown. A GE1/1 triple-GEM detector is
read out by 3,072 radial strips with 455 µrad pitch arranged
in eight η-sectors. We assembled a full-size GE1/1 prototype
of 1m length at Florida Tech and tested it in 20-120 GeV
hadron beams at Fermilab using Ar/CO2 70:30 and the RD51
scalable readout system. Four small GEM detectors with 2-D
readout and an average measured azimuthal resolution of 36 µrad
provided precise reference tracks. Construction of this largest
GEM detector built to-date is described. Strip cluster parameters,
detection efficiency, and spatial resolution are studied with
position and high voltage scans. The plateau detection efficiency
is [97.1 ± 0.2 (stat)]%. The azimuthal resolution is found to be
[123.5 ± 1.6 (stat)] µrad when operating in the center of the
efficiency plateau and using full pulse height information. The
resolution can be slightly improved by ∼ 10 µrad when correcting
for the bias due to discrete readout strips. The CMS upgrade
design calls for readout electronics with binary hit output.
When strip clusters are formed correspondingly without charge28 Sofia
University, Sofia, Bulgaria
University, Seoul, Korea
30 Seoul National University, Seoul, Korea
31 University of Seoul, Seoul, Korea
∗ Corresponding authors: vbhopatkar2010@my.fit.edu, hohlmann@fit.edu
29 Korea
Preprint number:
arXiv:1412.0194v1 [physics.ins-det] 30 Nov 2014
Measurement of the muon beam direction and
muon flux for the T2K neutrino experiment
K. Suzuki1,∗ , S. Aoki2 , A. Ariga3 , T. Ariga3 , F. Bay3,† C. Bronner4 , A. Ereditato3 ,
M. Friend5 , M. Hartz4,8 , T. Hiraki1 , A.K. Ichikawa1 , T. Ishida5 , T. Ishii5 ,
F. Juget3,‡ , T. Kikawa1,§ , T. Kobayashi5 , H. Kubo1 , K. Matsuoka1,¶ ,
T. Maruyama5 , A. Minamino1 , A. Murakami1,k , T. Nakadaira5 , T. Nakaya1 ,
K. Nakayoshi5 , Y. Oyama5 , C. Pistillo3 , K. Sakashita5 , T. Sekiguchi5 , S.Y. Suzuki5 ,
S. Tada5 , Y. Yamada5 , K. Yamamoto6 , and M. Yokoyama7
1
Department of Physics, Kyoto University, Kyoto, Japan
Kobe University, Kobe, Japan
University of Bern, Albert Einstein Center for Fundamental Physics, Laboratory for High Energy
Physics (LHEP), Bern, Switzerland
4
Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for
Advanced Study, University of Tokyo, Kashiwa, Japan
5
High Energy Accerlator Research Organization (KEK), Tsukuba, Ibaraki, Japan
6
Department of Physics, Osaka City University, Osaka, Japan
7
Department of Physics, University of Tokyo, Tokyo, Japan
8
TRIUMF, Vancouver, British Columbia, Canada
∗
E-mail: k.suzuki@scphys.kyoto-u.ac.jp
2
3
...............................................................................
The Tokai-to-Kamioka (T2K) neutrino experiment measures neutrino oscillations by
using an almost pure muon neutrino beam produced at the J-PARC accelerator facility.
The T2K muon monitor was installed to measure the direction and stability of the muon
beam which is produced together with the muon neutrino beam. The systematic error in
the muon beam direction measurement was estimated, using data and MC simulation,
to be 0.28 mrad. During beam operation, the proton beam has been controlled using
measurements from the muon monitor and the direction of the neutrino beam has been
tuned to within 0.3 mrad with respect to the designed beam-axis. In order to understand
the muon beam properties, measurement of the absolute muon yield at the muon monitor
was conducted with an emulsion detector. The number of muon tracks was measured
to be (4.06 ± 0.05) × 104 cm−2 normalized with 4 × 1011 protons on target with 250 kA
horn operation. The result is in agreement with the prediction which is corrected based
on hadron production data.
†
Present address: Institute for Particle Physics, ETH Zurich, Zurich, Switzerland
‡
Present address: Institute of Radiation Physics, University Hospital and University of Lausanne,
Lausanne, Switzerland
§
Present address: RCNP, Osaka University, Ibaraki, Osaka, Japan
¶
Present address: KMI, Nagoya University, Nagoya, Japan
k
Present address: Toshiba Corporation, Kawasaki, Japan
1
typeset using PTPTEX.cls
1. Introduction
The Tokai-to-Kamioka (T2K) experiment [1] is a long baseline neutrino oscillation experiment in Japan. The neutrino oscillation parameters are determined by measuring an
accelerator-produced neutrino beam before oscillation with the near detector and near the
oscillation maximum with the far detector. T2K began operation in January 2010. Since then,
data corresponding to a total of 6.63 × 1020 protons on target (p.o.t.) had been collected up
to May 2013.
The T2K muon monitor [2] was installed to monitor the muon beam which is produced
together with the neutrino beam from the decay of pions. As the muon monitor is the
only detector to monitor the beam spill-by-spill, our strategy is to monitor the muon beam
direction with a precision of 0.3 mrad for every beam spill, in order to better control the
neutrino beam for the neutrino oscillation measurement.
In this paper, we first provide an overview of the T2K experiment and the importance of a
precise measurement of the muon beam direction in Sec. 2. Section 3 gives an overview of the
components of the muon monitor. A method for reconstructing the profile of the muon beam
with the muon monitor is described in Sec. 4. In this section we also show the systematic
error in the beam direction measurement, which was estimated using both the actual beam
data and MC simulation. The stability of the beam direction and its intensity during the
T2K beam operation is discussed in Sec. 5. During the beam operation, measurements of
the absolute muon yield were conducted using an emulsion detector. This result, and a
comparison with the MC prediction, are shown in Secs. 6 and 7 respectively.
2. Overview of the T2K experiment
T2K consists of: a neutrino beamline, producing an intense muon neutrino beam; a near
detector complex, INGRID and ND280; and a far detector, Super-Kamiokande (Super-K).
Using this setup, the experiment aims to measure the neutrino oscillation parameters. An
overview of the T2K experiment is shown in Fig. 1. The Japan Proton Accelerator Research
Complex (J-PARC) is a facility situated in Tokai, Japan. A proton beam is accelerated up
to 30 GeV by the main ring synchrotron and is fast-extracted to the neutrino beamline. The
neutrino beamline consists of two components as shown in Fig. 2: a primary and secondary
beamline. In the primary beamline, the proton beam is transported to a graphite target every
2 to 3 seconds. The beam has a time structure of eight narrow bunches, 58 ns long with
581 ns intervals, in a single spill. The beam forms a two dimensional Gaussian distribution
of ∼4 mm 1σ width corresponding to ∼7 mm radius at the target. The target and other
equipment used to produce the neutrino beam is situated in the secondary beam line, whose
details are given in Sec. 2.1. The neutrino beam produced here is detected at ND280 and
Super-K, and the oscillation parameters are then measured.
2.1. Creation of the neutrino beam at the secondary beamline
Figure 3 provides an overview of the secondary beamline. All of the components in the
beamline are contained in a single volume of ∼ 1500 m3 filled with helium gas, which is
enclosed by a helium vessel. The proton beam, transported to the target via the primary
beamline, first enters a baffle which works as a collimator. After passing through the baffle,
2
arXiv:1412.0088v1 [physics.ins-det] 29 Nov 2014
Assembly and Bench Testing of a Spiral Fiber Tracker for
the J-PARC TREK/E36 Experiment
Makoto Tabata1,∗ , S´ebastien Bianchin2 , Michael D. Hasinoff3 , Robert S. Henderson2 ,
Keito Horie4 , Youichi Igarashi5 , Jun Imazato5 , Hiroshi Ito1 , Alexander Ivashkin6 ,
Hideyuki Kawai1 , Yury Kudenko6 , Oleg Mineev6 , Suguru Shimizu4 , Akihisa Toyoda5 , and
Hirohito Yamazaki7
1
Department of Physics, Chiba University, Chiba, Japan
Canada’s National Laboratory for Particle and Nuclear Physics (TRIUMF), Vancouver, Canada
3
Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada
4
Department of Physics, Osaka University, Toyonaka, Japan
5
Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization
(KEK), Tsukuba, Japan
6
Institute for Nuclear Research (INR) of the Russian Academy of Sciences (RAS), Moscow, Russia
7
Research Center for Electron Photon Science, Tohoku University, Sendai, Japan
2
E-mail: makoto@hepburn.s.chiba-u.ac.jp
This study presents the recent progress made in developing a spiral fiber tracker (SFT) for use in the
experiment TREK/E36 planned at the Japan Proton Accelerator Research Complex. This kaon decay experiment uses a stopped positive kaon beam to search for physics beyond the Standard Model
through precision measurements of lepton universality and through searches for a heavy sterile neutrino and a dark photon. Detecting and tracking positrons and positive muons from kaon decays are
of importance in achieving high-precision measurements; therefore, we designed and are developing
the new tracking detector using a scintillating fiber. The SFT was completely assembled, and in a
bench test, no dead channel was determined.
KEYWORDS: tracker, scintillating fiber, kaon decay, lepton universality, J-PARC TREK/E36
1. Introduction
We are currently developing a charged particle tracking detector, known as the spiral fiber tracker
(SFT) [1], for use in the E36 experiment [2–4] scheduled at the K1.1BR beam line in the Hadron
Experimental Facility of the Japan Proton Accelerator Research Complex (J-PARC). This positive
kaon decay experiment will search for physics beyond the Standard Model by testing lepton flavor
universality and searching for a heavy sterile neutrino and a dark photon [5–8]. To search for a violation of lepton universality, we focus, in particular, on precisely measuring the ratio of the kaon decay
widths RK = Γ(K + → e+ ν)/Γ(K + → µ+ ν) using a stopped kaon beam.
For this experiment, we are building a new TREK/E36 detector system (Fig. 1) by upgrading
the experiment E246 apparatus [9, 10], which was based on a twelve-sector superconducting toroidal
spectrometer that was previously used at the High Energy Accelerator Research Organization (KEK),
Tsukuba, Japan. Conducting high-precision measurements depends on efficiently identifying and
tracking charged particles (i.e., positrons and positive muons) from kaon decays. Particle identification is performed by measuring the time-of-flight (TOF) between the TOF1 and TOF2 scintillation
counters, threshold aerogel Cherenkov (AC) counters with a refractive index of 1.08, and lead (Pb)
glass Cherenkov (PGC) counters for robust analysis. As shown in Fig. 1(b), the TOF1 and AC counters surround the kaon stopping active target made of plastic scintillating fibers [11], and the TOF2
Prepared for submission to JHEP
arXiv:1412.0593v1 [hep-ph] 1 Dec 2014
Optimised sensitivity to leptonic CP violation from
spectral information: the LBNO case at 2300 km
baseline
S.K. Agarwalla,o L. Agostino,a M. Aittola,u A. Alekou,b B. Andrieu,x F. Antoniou,b
R. Asfandiyarov,aa D. Autiero,y O. B´
esida,k A. Balik,r P. Ballett,n I. Bandac,k
D. Banerjee,g W. Bartmann,b F. Bay,g B. Biskup,b A.M. Blebea-Apostu,i A. Blondel,aa
M. Bogomilov,c S. Bolognesi,k E. Borriello,ab I. Brancus,i A. Bravar,aa
M. Buizza-Avanzini,a D. Caiulo,y M. Calin,z M. Calviani,b M. Campanelli,d C. Cantini,g
G. Cata-Danil,i S. Chakraborty,ab N. Charitonidis,b L. Chaussard,y D. Chesneanu,i
F. Chipesiu,i P. Crivelli,g J. Dawson,a I. De Bonis,r Y. Declais,y P. Del Amo Sanchez,r
A. Delbart,k S. Di Luise,g D. Duchesneau,r J. Dumarchez,x I. Efthymiopoulos,b
A. Eliseev,w S. Emery,k T. Enqvist,u K. Enqvist,e L. Epprecht,g A.N. Erykalov,w
T. Esanu,z D. Franco,y M. Friend,h V. Galymov,y G. Gavrilov,w A. Gendotti,g
C. Giganti,x S. Gilardoni,b B. Goddard,b C.M. Gomoiu,z,i Y.A. Gornushkin,q
P. Gorodetzky,a A. Haesler,aa T. Hasegawa,h S. Horikawa,g K. Huitu,e A. Izmaylov,m
A. Jipa,z K. Kainulainen,f Y. Karadzhov,aa M. Khabibullin,m A. Khotjantsev,m
A.N. Kopylov,m A. Korzenev,aa S. Kosyanenko,w D. Kryn,a Y. Kudenko,m,t,s
P. Kuusiniemi,u I. Lazanu,z C. Lazaridis,b J.-M. Levy,x K. Loo,f J. Maalampi,f
R.M. Margineanu,i J. Marteau,y C. Martin-Mari,aa V. Matveev,m,q E. Mazzucato,k
A. Mefodiev,m O. Mineev,m A. Mirizzi,ab B. Mitrica,i S. Murphy,g T. Nakadaira,h
S. Narita,p D.A. Nesterenko,w K. Nguyen,g K. Nikolics,g E. Noah,aa Yu. Novikov,w
A. Oprima,i J. Osborne,b T. Ovsyannikova,m Y. Papaphilippou,b S. Pascoli,n
T. Patzak,a,l M. Pectu,i E. Pennacchio,y L. Periale,g H. Pessard,r B. Popov,x
M. Ravonel,aa M. Rayner,aa F. Resnati,g O. Ristea,z A. Robert,x A. Rubbia,g
K. Rummukainen,e A. Saftoiu,i K. Sakashita,h F. Sanchez-Galan,b J. Sarkamo,u
N. Saviano,ab,n E. Scantamburlo,aa F. Sergiampietri,g,j D. Sgalaberna,g
E. Shaposhnikova,b M. Slupecki,f D. Smargianaki,b D. Stanca,i R. Steerenberg,b
A.R. Sterian,i P. Sterian,i S. Stoica,i C. Strabel,b J. Suhonen,f V. Suvorov,w G. Toma,i
A. Tonazzo,a W.H. Trzaska,f R. Tsenov,c K. Tuominen,e M. Valram,i
G. Vankova-Kirilova,c F. Vannucci,a G. Vasseur,k F. Velotti,b P. Velten,b V. Venturi,b
T. Viant,g S. Vihonen,f H. Vincke,b A. Vorobyev,w A. Weber,v S. Wu,g N. Yershov,m
L. Zambelli,h M. Zitok
1
Now at Instituut voor Kern- en Stralingsfysica, KU Leuven, 3001 Leuven, Belgium.
Abstract: One of the main goals of the Long Baseline Neutrino Observatory (LBNO) is to
study the L/E behaviour (spectral information) of the electron neutrino and antineutrino
appearance probabilities, in order to determine the unknown CP-violation phase δCP and
discover CP-violation in the leptonic sector. The result is based on the measurement of the
appearance probabilities in a broad range of energies, covering the 1st and 2nd oscillation
maxima, at a very long baseline of 2300 km. The sensitivity of the experiment can be
maximised by optimising the energy spectra of the neutrino and anti-neutrino fluxes. Such
an optimisation requires exploring an extended range of parameters describing in details
the geometries and properties of the primary protons, hadron target and focusing elements
in the neutrino beam line. In this paper we present a numerical solution that leads to
an optimised energy spectra and study its impact on the sensitivity of LBNO to discover
leptonic CP violation. In the optimised flux both 1st and 2nd oscillation maxima play an
important role in the CP sensitivity. The studies also show that this configuration is less
sensitive to systematic errors (e.g. on the total event rates) than an experiment which
mainly relies on the neutrino-antineutrino asymmetry at the 1st maximum to determine
the existence of CP-violation.
EPJ Web of Conferences will be set by the publisher
DOI: will be set by the publisher
c Owned by the authors, published by EDP Sciences, 2014
Identified particle production and freeze-out properties in heavy-ion
collisions at RHIC Beam Energy Scan program
Sabita Das (for the STAR collaboration)1 , a
arXiv:1412.0499v1 [nucl-ex] 1 Dec 2014
1
Institute of Physics, Bhubaneswar-751005, India
Abstract. The first phase of Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider (RHIC)
was started in the year 2010 with the aim to study the several aspects of the quantum chromodynamics (QCD)
√
phase diagram. The Solenoidal Tracker At RHIC (STAR) detector has taken data at sNN = 7.7, 11.5, 19.6, 27,
and 39 GeV in Au+Au collisions in the years 2010 and 2011 as part of the BES programme. For these beam
energies, we present the results on the particle yields, average transverse mass and particle ratios for identified
particles in mid-rapidity (|y| < 0.1). The measured particle ratios have been used to study the chemical freezeout dynamics within the framework of a statistical model.
1 Introduction
finite-temperature QCD calculations on the lattice it is
theoretically established that the transition from QGP
To understand the properties of matter under extreme
to a hadron gas happens at high temperature and µB
conditions of high temperature or density, heavy-ion
close to zero and is a cross-over [6]. Several QCD-based
collision experiments are conducted at RHIC in BNL and
calculations [7] suggest existence of first-order phase
the LHC in CERN. These are the conditions, in which
transition at a lower T and large µB . Therefore, there
the deconfined phase of QCD matter, the Quark-Gluon
should be an end point for the first-oder phase transition
Plasma (QGP), is created. It is conjectured that the formed
in the QCD phase diagram, known as the critical point.
hot and dense partonic matter rapidly expands and cools
Several QCD based models and also calculations on
down. During the evolution it undergoes a transition back
lattice predict the existence of the critical point at high
to the hadronic matter [1, 2]. Both RHIC and LHC have
µB [8] and its exact location depends on the different
confirmed the formation of the QGP in central Au+Au
and Pb+Pb collisions [3, 4]. In QCD, there are three
conserved charges, baryon number B, electric charge Q
and strangeness S . Thus the equilibrium thermodynamic
state of QCD matter is completely determined by temperature T ch and the three chemical potentials µB , µQ ,
and µS corresponding to B, Q and S respectively. The
QCD phase diagram is plotted with the temperature (T )
as a function of baryon chemical potential (µB ) [5]. From
a e-mail: sabita@rcf.rhic.bnl.gov
model assumptions [9, 11–13]. It is worth to mention that
not all QCD-based models or lattice groups do predict the
existence of critical point [14].
Theoretically, the phase diagram is explored through nonperturbative QCD calculations on lattice which indicates
the energy scale can be explored experimentally. Now to
explore various aspects of the QCD phase diagram[15]
such as the search for the signals of phase boundary, and
the search the location of the critical point has become
Using MiniBooNE NCEL and CCQE cross section
results to constrain 3+1 sterile neutrino models
arXiv:1412.0461v1 [hep-ph] 1 Dec 2014
C Wilkinson, S Cartwright and L Thompson
Department of Physics and Astronomy, University of Sheffield,
Hicks Building, Hounsfield Road, Sheffield, S3 7RH, United Kingdom
E-mail: callum.wilkinson@sheffield.ac.uk
Abstract. The MiniBooNE NCEL and CCQE cross-section measurements (neutrino running)
are used to set limits in the ∆m2 − sin2 ϑµs plane for a 3+1 sterile neutrino model with a mass
splitting 0.1 ≤ ∆m2 ≤ 10.0 eV2 . GENIE is used, with a relativistic Fermi gas model, to relate
Eν and the reconstructed quantities measured. The issue of uncertainty in the underlying crosssection model and its effect on the sterile neutrino limits is explored, and robust sterile neutrino
limits are produced by fitting the sterile parameters and the axial-mass cross-section parameter
simultaneously.
1. Introduction
The large axial-mass (MA ) measured by MiniBooNE and other experiments has shown that
simple RFG models are inadequate to describe experimental data from quasi-elastic neutrino
scattering off nuclear targets. Although there has been a great deal of recent theoretical work
developing more sophisticated cross-section models, a clear picture has yet to emerge (a recent
summary can be found in [1]). Neutrino oscillation experiments use the measured event rate
to infer detailed information about the flux, so a flawed cross-section model may bias results.
There have been a number of studies investigating this bias in the context of three-neutrino
mixing measurements (see for example [2, 3, 4]). Similarly, such a bias should be investigated
for sterile neutrino results, which may be more susceptible as there is generally no way to measure
the unoscillated flux.
This work investigates the effect that uncertainty in an RFG cross-section model, with MA
as the only free parameter, has on sterile limits produced by a simple analysis of MiniBooNE
NCEL and CCQE cross-section data. It extends the work published in [5], which omitted the
CCQE data because of the lack of bin correlations. Limits are set in the ∆m2 − sin2 ϑµs plane
for a 3+1 sterile neutrino model with a mass splitting 0.1 ≤ ∆m2 ≤ 10.0 eV2 using a number
of different assumptions about the RFG model. We implicitly follow the assertion made in [6],
that inflating MA provides a reasonable description of the data, though it is understood that
this inflated MA value is effectively accounting for additional nuclear effects. We will refer to the
inflated axial-mass as MAeff from now on. A worthwhile extension of this work would be to look
at the effect that different cross-section models have on the sterile neutrino limits produced.
There are two choices to be made regarding the simple cross-section model, and we
demonstrate that their effects on the sterile limits are significant. The first is whether to
sequentially fit MAeff then the sterile neutrino parameters, which is only statistically sound if MAeff
and the sterile parameters are completely uncorrelated, or fit all parameters simultaneously. The
former procedure was used in the MiniBooNE-SciBooNE sterile analyses [7, 8], which used the
MiniBooNE measurement of MAeff as a constrained parameter in the fit, though it was noted that
EPJ Web of Conferences will be set by the publisher
DOI: will be set by the publisher
c Owned by the authors, published by EDP Sciences, 2014
Chemical freeze-out parameters in Beam Energy Scan Program of STAR at
arXiv:1412.0350v1 [nucl-ex] 1 Dec 2014
RHIC
Sabita Das (for the STAR collaboration)1 , a
1
Institute of Physics, Bhubaneswar-751005, India
Abstract. The STAR experiment at RHIC has completed its first phase of the Beam Energy Scan (BES-I)
program to understand the phase structure of the quantum chromodynamics (QCD). The bulk properties of the
√
system formed in Au+Au collisions at different center of mass energy sNN = 7.7, 11.5, 19.6, 27, and 39 GeV
have been studied from the data collected in the year 2010 and 2011. The centrality and energy dependence of
mid-rapidity (|y| < 0.1) particle yields, and ratios are presented here. The chemical freeze-out parameters are
extracted using measured particle ratios within the framework of a statistical model.
1 Introduction
onia [11] phase also appear in the QCD phase diagram in
addition to the confined and de-confined phases [12]. Par-
The heavy-ion collider experiments such as STAR at
RHIC, ALICE at LHC were designed to investigate matter similar to that formed at the very early stages of the
universe i.e. matter under extreme conditions of high temperature or density (or both) [1]. Similar to the matter in its
primordial state, a deconfined state of quarks and gluons is
created called Quark-Gluon Plasma (QGP) at both RHIC
and LHC [2, 3]. The QCD as the theory of strong interactions predicts a transition at sufficiently high temperature
T or baryon chemical potential µB from hadronic matter
to QGP state. So, by varying the T and µB in laboratory
we can study the phase transition associated with QCD
matter [4–7]. The major part of the QCD phase diagram,
which is generally known as the plot of T as a function of
µB , consists of two phases [8]. These are the high temperature QGP phase, where the relevant degrees of freedom are quarks and gluons, and the hadronic phase at low
temperature. Other interesting phases related to neutron
stars [9], color superconductivity [10], and the quarkya e-mail: sabita@rcf.rhic.bnl.gov
ticle yields in high energy heavy-ion experiments at different collision energies can be used to obtain the T and µB
that set up the chemical freeze-out line in the QCD phase
diagram. It appears to be very close to the phase boundary between QGP and hadronic phase, especially at low
µB . At high T and vanishing µB , finite temperature lattice QCD calculations has established the transition from
QGP to a hadron gas is a cross-over [13]. The existence
of a first-order phase transition has been predicted by several QCD-based calculations at lower T and µB [14]. The
QCD critical point is a feature of the phase diagram, where
the nature of the transition changes from a discontinuous
(first-order) transition to an analytic crossover [15–19].
To explore the freeze-out diagram, i.e. search the possible phase boundary line and search for the possible QCD
critical point, is a priority study at RHIC. For this, STAR
has completed the first phase of the Beam Energy Scan
(BES-I) program [20], collecting data from Au+Au collisions at center of mass energies of 7.7, 11.5, 14.5, 19.6,
arXiv:1412.0269v1 [hep-ph] 30 Nov 2014
Quasi-eikonal and quasi-U-matrix unitarization schemes
beyond the Black Disk Limit
E. Martynov
∗†
December 2, 2014
Abstract
Quasi-eikonal and quasi-U-matrix unitarization of the standard Regge-pole amplitude for α(0) > 1 have been considered. We show that some violation of unitarity
even at high energy exists in both models. We have found in quasi-eikonal model a
bump-oscillation structure of ImH(s, b) at large values of impact parameter b but where
ImH(s, b) is closed to the maximal value. We argue that it is possible to choose the
parameter regulating deviation of generalized models from pure eikonal or U-matrix
modes in order to restore unitarity.
It was shown in the recent paper [1] that the impact-parameter√amplitude H(s, b) extracted from pp elastic scattering data of the TOTEM experiment at s = 7 TeV [2] exceeds
the black disk (BDL) limit ImH(s, 0) = 1/2. We define H(s, b) as the following transformation of standard scattering amplitude (at high s)
1
H(s, b) =
8πs
Z∞
0
1
σt = ImA(s, 0),
s
dq qJ0 (qb)A(s, t = −~q2 ),
√
dσ
1
=
|A(s, t)|2 .
dt
16πs2
(1)
s = 7 TeV are shown in Fig. 1 (the figure is taken
The extracted data for ImH(s, b) at
from the [1]).
This result, provided that it will be confirmed at higher energies (8, 13, 14 TeV at LHC),
leads to the important consequences for many phenomenological models constructed within
a hypothesis that the BDL regime is realized in hadron elastic scattering at high energy.
First of all it concerns with a widely explored eikonal model
2iH (E) (s, b) = e2ih(s,b) − 1
(2)
where usually and in accordance with Regge approach an input amplitudes a(s, t) and h(s, b)
are assumed to have the following properties.
• Amplitude a(s, t) is presumably imaginary at least at small t.
• Amplitude h(s, b) ∝ i(−is/s0 )ε where ε > 0 and s0 = 1 GeV at fixed impact parameter
b and at s → ∞.
∗
†
Bogolyubov Institute for Theoretical Physics, Metrolologichna 14b, Kiev, UA-03680, Ukraine
email: martynov@bitp.kiev.ua
1
P REPARED FOR SUBMISSION TO JHEP
YITP-SB-14-49
arXiv:1412.0018v1 [hep-ph] 28 Nov 2014
Illuminating Dark Photons with High-Energy Colliders
David Curtin,a Rouven Essig,b Stefania Gori,c and Jessie Sheltond
a
Maryland Center for Fundamental Physics, University of Maryland, College Park, MD 20742, USA
C.N. Yang Institute for Theoretical Physics, Stony Brook University, Stony Brook, NY 11794, USA
c
Perimeter Institute for Theoretical Physics, 31 Caroline St. N, Waterloo, Ontario, Canada
d
1110 West Green Street Urbana, IL 61801, Dept of Physics, University of Illinois at Urbana-Champaign
b
E-mail: dcurtin1@umd.edu, rouven.essig@stonybrook.edu,
sgori@perimeterinstitute.ca, sheltonj@illinois.edu
A BSTRACT: High-energy colliders offer a unique sensitivity to dark photons, the mediators of a
broken dark U (1) gauge theory that kinetically mixes with the Standard Model (SM) hypercharge.
Dark photons can be detected in the exotic decay of the 125 GeV Higgs boson, h → ZZD → 4`,
and in Drell-Yan events, pp → ZD → ``. If the dark U (1) is broken by a hidden-sector Higgs
mechanism, then mixing between the dark and SM Higgs bosons also allows the exotic decay h →
ZD ZD → 4`. We show that the 14 TeV LHC and a 100 TeV proton-proton collider provide powerful
probes of both exotic Higgs decay channels. In the case of kinetic mixing alone, direct Drell-Yan
production offers the best sensitivity to ZD , and can probe & 9 × 10−4 (4 × 10−4 ) at the HLLHC (100 TeV pp collider). The exotic Higgs decay h → ZZD offers slightly weaker sensitivity,
but both measurements are necessary to distinguish the kinetically mixed dark photon from other
scenarios. If Higgs mixing is also present, then the decay h → ZD ZD can allow sensitivity to the
ZD for & 10−9 − 10−6 (10−10 − 10−7 ) for the mass range 2mµ < mZD < mh /2 by searching for
displaced dark photon decays. We also compare the ZD sensitivity at pp colliders to the indirect, but
model-independent, sensitivity of global fits to electroweak precision observables. We substantially
update previous work in the literature by performing a global electroweak fit of the dark photon model.
Electroweak precision measurements at LEP, Tevatron, and the LHC exclude as low as 3 × 10−2 .
Sensitivity can be improved by up to a factor of ∼ 2 with HL-LHC data, and an additional factor of
∼ 4 with ILC/GigaZ data.
A R X IV E P RINT: nnnn.nnnn
arXiv:1412.0619v1 [hep-ex] 1 Dec 2014
Low-Mass Dielectron Production in pp, p–Pb and
Pb–Pb Collisions with ALICE
Patrick Reichelt (for the ALICE Collaboration)
Institut f¨
ur Kernphysik, Goethe-Universit¨
at Frankfurt am Main, Germany
E-mail: preichelt@ikf.uni-frankfurt.de
Abstract. The ALICE Collaboration measures the production of low-mass dielectrons in pp,
p–Pb and Pb–Pb collisions at the LHC. The main detectors used in the analyses are the Inner
Tracking System, Time Projection Chamber and Time-Of-Flight detector, all located around
mid-rapidity. The production of virtual photons relative to the inclusive yield in pp collisions
is determined by analyzing the dielectron excess with respect to the expected hadronic sources.
The direct photon cross section is then calculated and found to be in agreement with NLO
pQCD calculations. Results from the invariant mass analysis in p–Pb collisions show an overall
agreement between data and hadronic cocktail. In Pb–Pb collisions, uncorrected backgroundsubtracted yields have been extracted in two centrality classes. A feasibility study for LHC
run 3 after the ALICE upgrade indicates the possibility for a future measurement of the early
effective temperature.
1. Introduction
The measurement of electron-positron pairs (dielectrons) in the low invariant mass region allows
studying the vacuum and in-medium properties of light vector mesons. Additionally, lowmass dielectrons are produced by internal conversion of virtual direct photons. They are
excellent probes to study all collision stages, since they pass through the created medium
almost unaffected. To quantify modifications of the dielectron production in heavy-ion collisions,
measurements in pp collisions serve as a reference, while the analysis of p-A collisions allows
disentangling cold from hot nuclear matter effects. In ALICE [1] at the LHC, dielectron
measurements are performed using the central barrel detectors around mid-rapidity. Electrons
can be identified via their specific energy loss in the Inner Tracking System (ITS) and the Time
Projection Chamber (TPC), combined with time-of-flight information from the TOF detector
[2]. In this proceedings we present a virtual direct photon measurement in pp collisions and the
invariant mass analyses in p–Pb and Pb–Pb collisions. Prospects of a future measurement in
Pb–Pb after the ALICE upgrade for LHC run 3 are also discussed.
√
2. Virtual direct photon production in pp collisions at s = 7 TeV
√
The analysis presented here is based on 3 · 108 minimum bias pp collisions at s = 7 TeV,
recorded in 2010. Fiducial cuts on transverse momentum (pT > 0.2 GeV/c) and pseudorapidity
(|η| < 0.8) are applied to electron candidates. A clean electron sample is achieved by cuts on the
time-of-flight and on the dE/dx in the TPC. Dielectron spectra are created for unlike-sign and
like-sign combinations of these particles. The unlike-sign distribution contains a superposition
arXiv:1412.0570v1 [hep-ex] 1 Dec 2014
Measurement of the charge asymmetry in dileptonic
decays of top quark pairs in pp collisions at
√
s = 7 TeV using the ATLAS detector
C Deterre1 on behalf of the ATLAS Collaboration
1
DESY, Notkestrasse 85, 22607 Hamburg, Germany
E-mail: 1 cecile.deterre@cern.ch
Abstract. A measurement of the top–antitop (tt¯) charge asymmetry is presented using
2011 LHC data collected by the ATLAS detector corresponding to an integrated luminosity
of 4.6 fb−1 at a centre-of-mass energy of 7 TeV. The analysis is performed in the dilepton
channel, and two different observables are studied: A``
C , based on the identified charged
¯
leptons, and AtCt , based on the reconstructed tt¯ final state. The asymmetries, measured to
tt¯
be A``
C = 0.024 ± 0.015 (stat.) ± 0.009 (syst.) and AC = 0.021 ± 0.025 (stat.) ± 0.017 (syst.), are
in agreement with the Standard Model predictions.
1. Introduction
This analysis [1] uses a data set corresponding to an integrated luminosity of 4.6 fb−1 of
Large Hadron Collider (LHC) proton–proton (pp) collisions at a centre-of-mass energy of 7 TeV
collected by the ATLAS [2] detector. It is performed in the dilepton channel of the tt¯ decay. The
¯
measured observables are the lepton-based charge asymmetry A``
C and the tt charge asymmetry
¯
t
t
``
AC . AC is defined as an asymmetry between positively and negatively charged leptons:
A``
C =
N (∆|η| > 0) − N (∆|η| < 0)
,
N (∆|η| > 0) + N (∆|η| < 0)
(1)
where ∆|η| = |η`+ | − |η`− |, η`+ (η`− ) is the pseudorapidity1 of the positively (negatively) charged
lepton and N is the number of events with positive or negative ∆|η|. The AtCt¯ corresponds to
the asymmetry in top and antitop quark rapidities2 :
¯
AtCt =
N (∆|y| > 0) − N (∆|y| < 0)
,
N (∆|y| > 0) + N (∆|y| < 0)
(2)
where ∆|y| = |yt | − |yt¯|, yt (yt¯) is the rapidity of the top (antitop) quark, and N is the number
of events with positive or negative ∆|y|.
In Standard Model (SM) tt¯ production, the asymmetry is absent at leading-order (LO)
Quantum Chromodynamics (QCD) and is introduced by the next-to-leading-order (NLO) QCD
1
The pseudorapidity is defined in terms of the polar angle θ as η = − ln tan(θ/2).
E+pz
The rapidity is defined as: y = 12 ln E−p
where E is the energy of the particle and pz is the component of the
z
momentum along the LHC beam axis.
2
Single Top Quark Measurements at the Tevatron
arXiv:1412.0500v1 [hep-ex] 1 Dec 2014
Manfredi Ronzani (on behalf of the CDF and D0 collaborations)
Albert-Ludwigs-Universit¨
at Freiburg, Physikalisches Institut, Hermann-Herder-Straße 3a,
D-79104 Freiburg, Germany
E-mail: manfredi.ronzani@cern.ch
Abstract. This paper reports the most recent measurements of single top quark production
performed by CDF and D0 collaborations in proton-antiproton collisions at Tevatron. Events
are selected in the lepton+jets final state by CDF and D0 and in the missing transverse energy
plus jets final state by CDF. The small single top signal in s-channel, t-channel and inclusive
s+t channel is separated from the large background by using different multivariate techniques.
We also present the most recent results on extraction of the CKM matrix element |Vtb | from
the single top quark cross section.
1. Introduction
The Fermilab Tevatron Collider was in operation until September
2011 and in the RunII it
√
provided 12 fb−1 of p¯
p collisions at center of mass energy of s = 1.96 TeV. The D0 and CDF
detectors recorded 10 fb−1 of proton-antiproton data per experiment.
The top quark was observed at the Tevatron by CDF [1] and D0 [2] in 1995 in tt¯ pairs
produced via strong interaction that is the top quark primary production mode. The Standard
Model (SM) predicts top quark to be produced also singly via electroweak interaction (single
top) with three different production processes (Fig.1): t-channel with the exchange of a virtual
W boson [3], s-channel with the W boson decaying into a top and an antibottom quarks [4] and
the Wt-channel with the associate production of a W boson and a top quark [5]. While the
first two production modes have a small but measurable cross section at Tevatron (around 2 pb
and 1 pb, respectively) the Wt production mode has a cross section of 0.25 pb, that makes its
contribution to the signal rate negligible.
Single top quark was first observed in 2009 by CDF [6] and D0 [7] experiments with an
inclusive search in s+t combined channels. The measurement in each single channel is done
differently at the Tevatron and LHC, taking in account the differences in the production cross
sections [3, 4, 5]. The t-channel is the dominant process at both the Tevatron and LHC and it
has been observed by D0 in 2011 [8] and then established by ATLAS [9] and CMS [10]. The
Wt-channel is visible only at the LHC and it has been observed by CMS collaboration at 8 TeV
[11]. The s-channel has a relatively small cross section at both Tevatron and LHC but at LHC
the signal to background ratio is smaller, that gives an advantage for the observation to the
Tevatron experiments.
The single top quark cross section measurement is proportional to |Vtb |2 , where |Vtb | is
element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. A direct measurement of |Vtb | is
therefore possible, that is also a test of the unitarity of the CKM matrix and it can constrain
extensions of the SM, for example with fourth quark generation [12].
December 2, 2014 5:25 WSPC/INSTRUCTION FILE
phipsi
venelin-proceedings-
arXiv:1412.0243v1 [hep-ex] 30 Nov 2014
International Journal of Modern Physics: Conference Series
c COPYRIGHT CERN on behalf of the NA62 Collaboration under CC BY-NC 3.0
MEASUREMENT OF THE RATIO OF THE CHARGED KAON
LEPTONIC DECAYS AT NA62
Venelin Kozhuharov∗
Laboratori Nazionali di Frascati - INFN, 40 E. Fermi, Frascati (Rome), Italy
Faculty of Physics, University of Sofia “St. Kl. Ohridski”, 5 J. Bourchier Blvd., Sofia, Bulgaria
Venelin.Kozhuharov@cern.ch
Received 30 11 2013
Revised 30 11 2013
The ratio of the leptonic charged kaon decays RK = Γ(K ± → e± ν)/Γ(K ± → µ± ν) is
sensitive to the structure of the week interactions and can be precisely calculated within
the Standard Model. Presence of New Physics can introduce a shift on its value of the
order of a percent. The NA62 experiment at CERN SPS used data from a dedicated run
in 2007 to perform a measurement of this ratio and probe the lepton universality. The
data analysis technique and the final results are presented.
Keywords: kaon decays, lepton universality, rare decays
PACS numbers:13.20.Eb, 11.30.Hv
1. Introduction
Within the Standard Model the dilepton charged pseudoscalar meson decays proceed as tree level processes through a W exchange. However, the helicity conservation leads to a strong suppression of the electron mode. The Standard Model (SM)
expression for the ratio RK = Γ(Ke2)/Γ(Kµ2) is a function of the masses of the
∗ Speaker, for the NA62 Collaboration: F. Ambrosino, A. Antonelli, G. Anzivino, R. Arcidiacono,
W. Baldini, S. Balev, S. Bifani, C. Biino, A. Bizzeti, B. Bloch-Devaux, V. Bolotov, F. Bucci,
A. Ceccucci, P. Cenci, C. Cerri, G. Collazuol, F. Costantini, A. Cotta Ramusino, D. Coward,
G. D’Agostini, P. Dalpiaz, H. Danielsson, G. Dellacasa, D. Di Filippo, L. DiLella, N. Doble, V. Duk,
J. Engelfried, K. Eppard, V. Falaleev, R. Fantechi, M. Fiorini, P.L. Frabetti, A. Fucci, S. Gallorini,
L. Gatignon, E. Gersabeck, A. Gianoli, S. Giudici, E. Goudzovski, S. Goy Lopez, E. Gushchin,
B. Hallgren, M. Hita-Hochgesand, E. Iacopini, E. Imbergamo, V. Kekelidze, K. Kleinknecht,
V. Kozhuharov, V. Kurshetsov, G. Lamanna, C. Lazzeroni, M. Lenti, E. Leonardi, L. Litov,
D. Madigozhin, A. Maier, I. Mannelli, F. Marchetto, P. Massarotti, M. Misheva, N. Molokanova,
M. Moulson, S. Movchan, M. Napolitano, A. Norton, T. Numao, V. Obraztsov, V. Palladino,
M. Pepe, A. Peters, F. Petrucci, B. Peyaud, R. Piandani, M. Piccini, G. Pierazzini, I. Popov,
Yu. Potrebenikov, M. Raggi, B. Renk, F. Reti`
ere, P. Riedler, A. Romano, P. Rubin, G. Ruggiero,
A. Salamon, G. Saracino, M. Savri´
e, V. Semenov, A. Sergi, M. Serra, S. Shkarovskiy, M. Sozzi,
T. Spadaro, P. Valente, M. Veltri, S. Venditti, H. Wahl, R. Wanke, A. Winhart, R. Winston,
O. Yushchenko, A. Zinchenko.
1
arXiv:1412.0240v1 [hep-ex] 30 Nov 2014
EPJ Web of Conferences will be set by the publisher
DOI: will be set by the publisher
c Owned by the authors, published by EDP Sciences, 2014
NA62 experiment at CERN SPS
Venelin Kozhuharov1,2 , a
1
2
Laboratori Nazionali di Frascati - INFN, 40 E. Fermi, 00044 Frascati (Rome), Italy
Faculty of Physics, University of Sofia “St. Kl. Ohridski”, 5 J. Bourchier Blvd., 1164 Sofia, Bulgaria
Abstract. The NA62 experiment at SPS is a continuation of the long standing CERN
kaon physics program. The high statistics and the unprecedent precision allow to probe
the Standard Model and test the description of the strong interactions at low energy. The
final results on the the lepton universality test by measuring the ratio RK = Γ(K + →
e+ ν)/Γ(K + → µ+ ν) and the study of the K ± → π± γγ decay are presented. The major
goal of the NA62 experiment is to perform a measurement of the Br(K + → π+ ν¯ν) with
a precision of 10% in two years of data taking. The detector setup together with the
analysis technique is described.
1 Introduction
The high intensity approach of the fixed target experiments as opposed to the highest energy collisions
provides a unique opportunity to address the Standard model through precision measurements.
The phenomena in kaon physics allow to probe both the low energy behaviour of the strong interactions as well as the high energy weak scale through loop processes. Special attention should be
given to the rare kaon decays since some of them could achieve sizeable contribution in the presence
a e-mail: Venelin.Kozhuharov@cern.ch
Speaker, for the NA62 Collaboration: G. Aglieri Rinella, F. Ambrosino, B. Angelucci, A. Antonelli, G. Anzivino, R. Arcidiacono, I. Azhinenko, S. Balev, J. Bendotti, A. Biagioni, C. Biino, A. Bizzeti, T. Blazek, A. Blik, B. Bloch-Devaux, V. Bolotov, V.
Bonaiuto, D. Britton, G. Britvich, N. Brook, F. Bucci, V. Buescher, F. Butin, E. Capitolo, C. Capoccia, T. Capussela, V. Carassiti, N. Cartiglia, A. Cassese, A. Catinaccio, A. Cecchetti, A. Ceccucci, P. Cenci, V. Cerny, C. Cerri, O. Chikilev, R. Ciaranfi,
G. Collazuol, P. Cooke, P. Cooper, G. Corradi, E. Cortina Gil, F. Costantini, A. Cotta Ramusino, D. Coward, G. D’Agostini,
J. Dainton, P. Dalpiaz, H. Danielsson, J. Degrange, N. De Simone, D. Di Filippo, L. Di Lella, N. Dixon, N. Doble, V. Duk, V.
Elsha, J. Engelfried, V. Falaleev, R. Fantechi, L. Federici, M. Fiorini, J. Fry, A. Fucci, S. Gallorini, L. Gatignon, A. Gianoli, S.
Giudici, L. Glonti, A. Goncalves Martins, F. Gonnella, E. Goudzovski, R. Guida, E. Gushchin, F. Hahn, B. Hallgren, H. Heath,
F. Herman, E. Iacopini, O. Jamet, P. Jarron, K. Kampf, J. Kaplon, V. Karjavin, V. Kekelidze, A. Khudyakov, Yu. Kiryushin,
K. Kleinknecht, A. Kluge, M. Koval, V. Kozhuharov, M. Krivda, J. Kunze, G. Lamanna, C. Lazzeroni, R. Leitner, R. Lenci,
M. Lenti, E. Leonardi, P. Lichard, R. Lietava, L. Litov, D. Lomidze, A. Lonardo, N. Lurkin, D. Madigozhin, G. Maire, A.
Makarov, I. Mannelli, G. Man- nocchi, A. Mapelli, F. Marchetto, P. Massarotti, K. Massri, P. Matak, G. Mazza, E. Menichetti,
M. Mirra, M. Misheva, N. Molokanova, J. Morant, M. Morel, M. Moulson, S. Movchan, D. Munday, M. Napolitano, F. Newson, A. Norton, M. Noy, G. Nuessle, V. Obraztsov, S. Padolski, R. Page, V. Palladino, A. Pardons, E. Pedreschi, M. Pepe, F.
Perez Gomez, F. Petrucci, R. Piandani, M. Piccini, J. Pinzino, M. Pivanti, I. Polenkevich, I. Popov, Yu. Potrebenikov, D. Protopopescu, F. Raffaelli, M. Raggi, P. Riedler, A. Romano, P. Rubin, G. Ruggiero, V. Russo, V. Ryjov, A. Salamon, G. Salina, V.
Sam- sonov, E. Santovetti, G. Saracino, F. Sargeni, S. Schifano, V. Semenov, A. Sergi, M. Serra, S. Shkarovskiy, A. Sotnikov,
V. Sougonyaev, M. Sozzi, T. Spadaro, F. Spinella, R. Staley, M. Statera, P. Sutcliffe, N. Szilasi, D. Tagnani, M. Valdata-Nappi,
P. Valente, V. Vassilieva, B. Velghe, M. Veltri, S. Venditti, M. Vormstein, H. Wahl, R. Wanke, P. Wertelaers, A. Winhart, R.
Winston, B. Wrona, O. Yushchenko, M. Zamkovsky, A. Zinchenko
EUROPEAN ORGANISATION FOR NUCLEAR RESEARCH (CERN)
arXiv:1412.0237v1 [hep-ex] 30 Nov 2014
CERN-PH-EP-2014-158
Submitted to: JHEP
Search for anomalous production of prompt same-sign lepton
pairs and pair-produced doubly charged Higgs bosons with
√
s = 8 TeV pp collisions using the ATLAS detector
The ATLAS Collaboration
Abstract
A low-background inclusive search for new physics in events with same-sign dileptons is presented. The search uses proton–proton collisions corresponding to 20.3 fb−1 of integrated luminosity
taken in 2012 at a centre-of-mass energy of 8 TeV with the ATLAS detector at the LHC. Pairs of isolated leptons with the same electric charge and large transverse momenta of the type e± e± , e± µ± ,
and µ± µ± are selected and their invariant mass distribution is examined. No excess of events above
the expected level of Standard Model background is found. The results are used to set upper limits
on the cross sections for processes beyond the Standard Model. Limits are placed as a function of th
e dilepton invariant mass within a fiducial region corresponding to the signal event selection criteria.
Exclusion limits are also derived for a specific model of doubly charged Higgs boson production.
c 2014 CERN for the benefit of the ATLAS Collaboration.
Reproduction of this article or parts of it is allowed as specified in the CC-BY-3.0 license.
arXiv:1412.0227v1 [hep-ex] 30 Nov 2014
Measurement of the fraction of top quark pair events
produced via gluon-gluon fusion at the Tevatron in
lepton+jets final states
Sungwoong Choa , Suyong Choia , Sehwook Leea , JaeHoon Lima , and
SungWoo Younb
a
Korea University,
b
University of Maryland
E-mail: swcho@fnal.gov
Abstract. We report a measurement √
of the fraction of top quark pair events produced via
s = 1.96 TeV in lepton+jets final states using the
gluon-gluon fusion in p¯
p collisions at
full RunII data set corresponding to 9.7 fb−1 of integrated luminosity collected by the DØ
experiment. We utilize a boosted decision tree to distinguish top quark pair events produced by
q q¯ annihilation and gg fusion. We perform a template fit to extract the tt¯ production fraction
via gg fusion and find fgg = 0.096 ± 0.039 (stat.) +0.077
−0.062 (syst.).
1. Introduction
The standard model (SM) predicts that at the Tevatron tt¯ events are produced predominantly
by either quark-antiquark (q q¯) annihilation and gg fusion with fractions of ≈ 85% and ≈ 15%,
respectively. However, this prediction for the fraction of tt¯ production from gg fusion can vary
from 10% to 20% due to uncertainties on the parton density functions (PDF) [1] [2]. A precise
measurement of this quantity will be helpful to have better understanding of the structure of
proton. Since different production mechanisms can result in significantly different kinematic
properties [3], a deviation from the SM calculations may also suggest the possible existence of
new physics.
The top quark, with a mass of about 175 GeV/c2 , has a life time that is an order of magnitude
smaller than the typical quantum chromodynamics (QCD) hadronization time of ≈ 5 × 10−24 s
[4]. As a consequence, the spin information of the top quark is preserved to its decay particles.
Due to different spin structures for different production modes, the angular distributions of decay
particles are useful to distinguish between q q¯ annihilation and gg fusion events. Furthermore,
the gluon has a large degrees of freedom in color charge state than a quark does, the former is
involved with the QCD effects such as initial/final state radiations more than the latter, resulting
in, for example, extra partons and thus affecting the kinematic distributions of the final state
particles.
To separate tt¯ events produced through q q¯ annihilation and gg fusion, we utilize the boosted
decision tree (BDT) [5] in the toolkit for multivariate analysis method with ROOT (TMVA)
package. We use 16 input variables sensitive to the production mechanism, which will be
described in Sec. 2. We construct the BDT templates from simulated events for q q¯ annihilation
arXiv:1412.0181v1 [hep-ex] 30 Nov 2014
Search for a light charged Higgs boson decaying
into cs¯ at CMS
Gouranga Kole∗†
Tata Institute of Fundamental Research
Homi Bhabha Road, Colaba
Mumbai 400005, India
E-mail: gouranga@tifr.res.in
We present results on the search for a light charged Higgs boson that can be produced in the decay
of a top quark and later decays into a charm and an antistrange quark. The analysis is performed
using 19.7 fb−1 pp collison data recorded with the CMS detector at LHC.
Prospects for Charged Higgs Discovery at Colliders - CHARGED 2014,
16-18 September 2014
Uppsala University, Sweden
∗ Speaker.
† On
behalf of the CMS Collaboration
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
Search for H + → cs¯ at CMS
http://pos.sissa.it/
Gouranga Kole
1. Introduction
A Higgs boson has recently been discovered by ATLAS [1] and CMS [2] with a mass close to
125 GeV and properties, within uncertainties of the available data, consistent with those expected
from the standard model (SM). Although this would complete the SM, still the latter cannot be the
full story having many missing links such as dark matter, baryon asymmetry and gravity. Several
extensions to the SM have been proposed to address these inconsistent features. The minimal
supersymmetric standard model (MSSM) is one such model that contains two Higgs doublets,
resulting in five physical Higgs states: a light and heavy CP-even h and H, a CP-odd A, and two
charged Higgs bosons H ± . At tree level, the MSSM Higgs sector can be expressed in terms of two
parameters, which are usually chosen to be the mass of the CP-odd Higgs boson (mA ) and the ratio
of the vacuum expectation values of the two Higgs doublets (tan β ).
The lower limit on the charged Higgs boson mass is 78.6 GeV, as determined by LEP experiments [3, 4]. If the mass of the charged Higgs boson is smaller than the mass difference between
the top and the bottom quarks, the top can decay via t → H + b. For tan β < 1, the charged Higgs
boson preferentially decays to a charm and an antistrange quark (cs).
¯ In the two Higgs doublet
model of type I and Y the branching fraction B(H + → cs)
¯ is larger than 10% for any value of
tan β , while in type II and X it can reach up to 100% for tan β < 1 [5]. In this study, we assume
B(H + → cs)
¯ to be 100%. Recently ATLAS has set an upper limit on B(t → H + b) between 5%
and 1% for charged Higgs masses in the range 90-150 GeV [6].
The presence of the t → H + b, H + → cs¯ decay channel alters the event yield for t t¯ pairs having
hadronic jets in the final state, compared to the SM prediction. The search for a charged Higgs
¯ where
boson is thus sensitive to the decays of the top pairs t t¯ → H ± bW ∓ b¯ and t t¯ → H ± bH ∓ b,
the charged Higgs boson decays into a charm and an antistrange quark. We perform a model
independent search [7] for the charged Higgs boson in the t t¯ → H ± bW ∓ b¯ → µ + ETmiss + jets final
state, where the W boson decays to a muon and a neutrino (leading to missing transverse energy
ETmiss ) and the H + decays to cs.
¯ The contribution of the process t t¯ → H ± bH ∓ b¯ is expected to be
negligible in the above final state. Figure 1 shows the dominant Feynman diagrams for this final
state both in the SM t t¯ process as well as the same in presence of the H + boson.
2. CMS Detector and Object Reconstruction
The distinguishing features of the CMS detector [8] are a 6 m long solenoidal magnet that produces 3.8 T magnetic field, a fully silicon-based tracking device, a PbWO4 crystal electromagnetic
calorimeter, a brass-scintilltor sandwich hadron calorimeter, and an excellent muon system. All
physics objects used in the analysis are reconstructed with the particle flow (PF) algorithm, essentially combining information from the aforementioned subdectectors. Muons are reconstructed by
matching the tracks in the silicon tracker with the hits in the muon system. Jets are reconstructed
based on the anti-kT algorithm with a cone radius parameter R = 0.5. The ETmiss is defined as the
negative vector sum of the transverse momenta (pT ) of all PF candidates. To identify jets originating from a b quark, we apply the b-jet identification criteria that involve the use of secondary
vertices together with track-based lifetime information.
2
arXiv:1412.0139v1 [hep-ex] 29 Nov 2014
Experimental results on tt¯ + W/Z/γ and SM top
couplings from the Tevatron and the LHC
Tamara V´
azquez Schr¨
oder for the ATLAS, CDF, CMS and D0
Collaborations
II. Physikalisches Institut, Georg-August Universit¨
at G¨
ottingen, G¨
ottingen, Germany
E-mail: tamara.vazquez-schroeder@phys.uni-goettingen.de
Abstract. Experimental results from the CDF and D0 Collaborations at the Tevatron and
the ATLAS and CMS Collaborations at the LHC on the processes related to probing top quark
couplings are presented. Evidence of both tt¯Z and tt¯W processes is reported. All measurements
are in agreement with the SM expectations.
1. Motivation
The top quark was discovered in 1995 by the CDF and D0 Collaborations [1, 2]. It couples to the
Standard Model fields through its gauge and Yukawa interactions. Some of these couplings have
been investigated at the Tevatron, through studies of the W tb vertex and the tt¯γ production,
while others, such as the tt¯Z and tt¯H production, are becoming accessible only with the high
statistics top quark sample at the LHC, also called for this reason a ‘top quark factory’. At
hadron colliders, the first evidence of the coupling of the top quark to the γ, Z, and H boson
will come from the production rate, while constraints on the coupling of the top quark with the
W boson come from both the top quark decay and the single top production. Given its large
mass, the top quark may play a special role in the electroweak symmetry breaking (EWSB) and
therefore, new physics related to EWSB may be found first in top quark precision measurements.
Possible new physics signals would cause deviations of the top quark couplings tZ, tγ, and W tb,
from the SM prediction.
2. Wtb coupling
Information on the coupling of the top quark to the W boson can be obtained from the top
quark decay and electroweak single top production.
2.1. W-helicity measurements
Since the top quark decays almost exclusively as t → W + b, the measurement of the W boson
helicity in top decays probes the structure of the W tb vertex, which in the Standard Model
(SM) is V-A. Since W bosons are produced as on-shell particles in top quark decays, their
polarisation can be longitudinal, left-handed or right-handed. The fractions with a certain
polarisation, F0 , FL and FR , can be extracted from measurements of the angular distribution of
arXiv:1412.0106v1 [hep-ex] 29 Nov 2014
Measurement of Top-Quark Polarization in t-channel
Single-Top Production
Matthias Komm
Centre for Cosmology, Particle Physics and Phenomenology, Universit´e catholique de Louvain,
1348 Louvain-la-Neuve, Belgium
E-mail: Matthias.Komm@CERN.ch
Abstract. The measurement of the top quark polarization, sensitive to the electroweak
coupling structure, in t-channel single-top production is presented. Events are analyzed
corresponding to an integrated luminosity of approximately 20 fb−1 recorded with the CMS
√
detector during pp collisions at s = 8 TeV. By requiring one isolated lepton (muon or
electron), two jets, and missing transverse energy, an angular asymmetry, sensitive to the
polarization of the top quark, is reconstructed in the top-quark rest frame. The corresponding
angular asymmetry at parton level is inferred from data in a phase space with enhanced singletop t-channel candidates through unfolding. Remaining background contributions are estimated
through a ML-fit and subtracted. A polarization of Pt = 0.82 ± 0.12 (stat.) ± 0.32 (syst.) is
measured assuming a spin-analyzing power of the charged lepton stemming from the top decay
of 100%.
1. Introduction
In the theory of particle physics, the Standard Model (SM), electroweak interactions between
fermions via charged currents are maximally parity violating. Only left-handed fermions (or
right-handed anti-fermions) can couple to W bosons through a V-A coupling structure.
The top quark offers an unique possibility amongst all quarks to probe this prediction because
of its very short lifetime below the hadronization time scale. Therefore, its spin orientation stays
encoded in the angular distribution of its decay products.
An observable sensitive to the electroweak top quark coupling structure is given in t-channel
single top-quark production by the forward-backward asymmetry
(top)
A=
N (cos θl,q
(top)
N (cos θl,q
(top)
> 0) − N (cos θl,q
> 0) +
(top)
(top)
N (cos θl,q
< 0)
1
= Pt αl
2
< 0)
(1)
in the top-quark rest frame, where θl,q denotes the angle between the lepton and the light (u,
d, s, c) quark which may also be referred to as spectator quark. The polarization, Pt , denotes the
alignment of the top-quark spin with the light-quark momentum and the spin-analyzing power,
αl , quantifies the alignment of lepton with the top-quark spin. Theoretical calculations show
that the particular V-A structure leads to a high polarization, Pt = 0.98, and spin analyzing
power αl = 1 [1].
arXiv:1412.0104v1 [hep-ex] 29 Nov 2014
Experimental results with boosted top quarks in the
final state
Johannes Erdmann for the ATLAS and CMS collaborations
Technische Universit¨
at Dortmund, Fakult¨
at Physik, Experimentalphysik IV,
Otto-Hahn-Straße 4, 44227 Dortmund, Germany
E-mail: johannes.erdmann@cern.ch
√
Abstract. An overview of analyses using data at s = 7 TeV and 8 TeV of proton-proton
collisions at the LHC is presented. These analyses use boosted techniques to search for new
phenomena involving top quarks and to measure the production of top quarks at high transverse
momenta. Such techniques involve top-quark tagging algorithms, boson-tagging algorithms, and
strategies for b-tagging and lepton identification in the environment where the top quark decay
products are close to each other. The strategies are optimized for the different final states and
for different ranges of the transverse momenta of the particles involved, improving on traditional
resolved analysis strategies.
1. Introduction
√
With roughly 5 fb−1 of LHC proton-proton (pp) collision data at s = 7 TeV and roughly
20 fb−1 at 8 TeV available for analysis, the ATLAS and CMS collaborations are facing the
challenge of identifying top quarks in the boosted regime with top-tagging techniques [1] (toptagging). The traditional resolved strategy of identifying individual jets originating from the
decay of hadronically decaying top quarks fails for Lorentz boosts of the top quark for which
the decay products overlap in η–φ space. With the use of larger jet radii, however, all decay
products of hadronically decaying top quark may be contained in one single jet (large-R jets).
The substructure of such jets can be used to distinguish the three-prong decay of the top quark
from the background processes, in particular from jets originating from light quarks or gluons.
Similar strategies are used for the identification of hadronic decays of W , Z and Higgs bosons
(boson-tagging): W → q q¯0 , Z → q q¯ and H → b¯b. The identification of jets originating
from b-quarks, is more challenging in the boosted regime, because of nearby activity in the
tracking detector and the high transverse momentum of b-quarks. The application of b-tagging
to small-R subjets of the large-R jet (subjet b-tagging), however, improves the performance of
the top-tagging algorithms, and allows for multiple b-tags inside a single large-R jet as used
in the identification of hadronically decaying Higgs bosons. Moreover, lepton identification is
more challenging in the boosted regime, because nearby activity renders traditional isolation
criteria inefficient. Hence, analyses using leptons often make use of modified lepton-isolation
criteria. The top-tagging, boson-tagging and b-tagging strategies used by the ATLAS and CMS
collaborations in the boosted regime are described in several documents [2, 3, 4, 5, 6], where
also predictions from Monte Carlo (MC) simulations are compared to pp collision data.
CERN-PH-TH-2014-232
Towards realistic models from Higher-Dimensional theories
with Fuzzy extra dimensions∗
arXiv:1412.0438v1 [hep-th] 1 Dec 2014
D.Gavriil1 , G.Manolakos1 , G.Zoupanos1,2
1
Physics Department, National Technical University,
Zografou Campus, GR-15780 Athens, Greece
2
Theory Group, Physics Department
Cern, Geneva, Switzerland
E-mails: d.gavriil@yahoo.gr , gmanol@central.ntua.gr , George.Zoupanos@cern.ch
Abstract
We briefly review the Coset Space Dimensional Reduction (CSDR) programme and the best model constructed so far and then we present some details of the corresponding programme in the case that the extra
dimensions are considered to be fuzzy. In particular, we present a four-dimensional N = 4 Super Yang Mills
Theory, orbifolded by Z3 , which mimics the behaviour of a dimensionally reduced N = 1, 10-dimensional
gauge theory over a set of fuzzy spheres at intermediate high scales and leads to the trinification GUT SU (3)3
at slightly lower, which in turn can be spontaneously broken to the MSSM in low scales.
Keywords: coset space dimensional reduction, unification, fuzzy spheres, orbifold projection
1
Introduction
enter the theory, because of the ad hoc introduction
of the Higgs and Yukawa sectors, is a major problem demanding solution. This embarrassment can be
overcome by considering that those sectors originate
from a higher dimensional theory. Various frameworks
starting with the Coset Space Dimensional Reduction
(CSDR) [21–23] and the Scherk-Schwarz [24] reduction schemes suggest that unification of the gauge and
Higgs sectors can take place making use of higher
dimensions. This means that the four-dimensional
gauge and Higgs fields are the surviving components of
the reduction procedure of the gauge fields of a pure
higher-dimensional gauge theory. Furthermore, the
addition of fermions in the higher-dimensional gauge
theory leads naturally (after CSDR) to Yukawa couplings in four dimensions. The last step in this unified description in high dimensions is to relate the
gauge and fermion fields, which can be achieved by
demanding that the higher-dimensional gauge theory
is N = 1 supersymmetric, i.e. the gauge and fermion
fields are members of the same vector supermultiplet.
In order to maintain an N = 1 supersymmetry after dimensional reduction, Calabi-Yau (CY) manifolds
Since 1970’s there has been an intense pursuit of
unification, that is the establishment of a single theoretical model describing all interactions. Profound
research activity has resulted in two very interesting frameworks, namely Superstring Theories [1] and
Non-Commutative Geometry [2]. Both approaches, although developing independently, share common unification targets and aim at exhibiting improved renormalization properties in the ultraviolet regime as compared to ordinary field theories. Moreover, these two
(initially) different frameworks were bridged together
after realizing that a Non-Commutative gauge theory
can describe the effective physics on D-branes whilst
a non-vanishing background antisymmetric field is
present [3].
Significant progress has recently been made regarding the dimensional reduction of the E8 × E8 Heterotic String using non-symmetric coset spaces [4][20], in the presence of background fluxes and gaugino condensates. It is widely known that the large
number of Standard Model’s free parameters which
∗ Based on a talk presented at the International Conference "Quantum Field Theory and Gravity (QFTG’14)" (Tomsk, July 28 - August 3,
2014) by G.Z. (invited main speaker).
1
arXiv:1412.0407v1 [astro-ph.CO] 1 Dec 2014
Fitting BICEP2 with defects, primordial
gravitational waves and dust
Joanes Lizarraga1 , Jon Urrestilla1 , David Daverio2 , Mark
Hindmarsh3,4 , Martin Kunz2,5 , Andrew R. Liddle6
1
Department of Theoretical Physics, University of the Basque Country UPV/EHU, 48080
Bilbao, Spain
2
D´epartement de Physique Th´eorique & Center for Astroparticle Physics, Universit´e de
Gen`eve, Quai E. Ansermet 24, CH-1211 Gen`eve 4, Switzerland
3
Department of Physics & Astronomy, University of Sussex, Brighton, BN1 9QH, United
Kingdom
4
Department of Physics and Helsinki Institute of Physics, PL 64, FI-00014 University of
Helsinki, Finland
5
African Institute for Mathematical Sciences, 6 Melrose Road, Muizenberg, 7945, South Africa
6
Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ,
United Kingdom
E-mail: joanes.lizarraga@ehu.es
Abstract. In this work we discuss the possibility of cosmic defects being responsible for the
B-mode signal measured by the BICEP2 collaboration. We also allow for the presence of other
cosmological sources of B-modes such as inflationary gravitational waves and polarized dust
foregrounds, which might contribute to or dominate the signal. On the one hand, we find that
defects alone give a poor fit to the data points. On the other, we find that defects help to improve
the fit at higher multipoles when they are considered alongside inflationary gravitational waves
or polarized dust. Finally, we derive new defect constraints from models combining defects and
dust. This proceeding is based on previous works [1, 2].
1. Introduction
The recent detection of B-mode polarization on large angular scales [3] has opened a new window
to test and constrain models that predict primordial perturbations. The leading candidate, as
claimed by the BICEP2 team, is primordial inflationary gravitational waves. For a tensorto-scalar ratio r of around 0.2, these give a good match to the spectral shape in the region
` ≈ [40 150].
An alternative mechanism of generating primordial B-modes is the presence of cosmic defects.
Even though their relative contribution to the temperature power spectrum is expected to be
sub-dominant, they can still contribute importantly to the B-mode polarization. We explore
whether cosmic defects could explain or help other primary contributors fit the data better.
Recently some works have reported that the measurements made by BICEP2 can have a nonnegligible astrophysical source: polarized dust foregrounds [4, 5, 6]. We extended our primary
analysis including such a possible source.
Hyperfine Interactions manuscript No.
(will be inserted by the editor)
Pion-assisted N ∆ and ∆∆ dibaryons, and beyond
arXiv:1412.0198v1 [nucl-th] 30 Nov 2014
Avraham Gal
Received: date / Accepted: date
Abstract Experimental evidence for I(J P )=0(3+ ) ∆∆ dibaryon D03 (2370)
has been presented recently by the WASA-at-COSY Collaboration. Here I
review new hadronic-basis Faddeev calculations of L = 0 nonstrange pionassisted N ∆ and ∆∆ dibaryon candidates. These calculations are so far the
only ones to reproduce the relatively small D03 (2370) width of 70–80 MeV.
Predictions are also given for the location and width of D30 , the I(J P )=3(0+ )
exotic partner of D03 (2370). Extensions to strangeness S=−1 dibaryons are
briefly discussed.
Keywords Faddeev equations · nucleon-nucleon interactions · pion-baryon
interactions · dibaryons
PACS 11.80.Jy, 13.75.Cs, 13.75.Gx, 21.45.-v
1 Introduction
The WASA-at-COSY Collaboration has presented recently striking evidence
for a I(J P ) = 0(3+ ) ∆∆ dibaryon some 80–90 MeV below the ∆∆ threshold,
with a relatively small width of Γ ≈ 70 − 80 MeV, by observing a distinct
resonance in the energy spectrum of pn → dππ reactions [1,2] as shown in
Fig. 1–left. Isospin I = 0 is uniquely fixed in this particular π 0 π 0 production
reaction and the spin-parity 3+ assignment follows from the measured deuteron
and pions angular distributions, assuming s-wave decaying ∆∆ pair. The shape
2
of the M√
dπ distribution on the right panel supports ∆∆ assignment and its
peak at s ≈ 2.13 GeV, almost at the D12 (2150) N ∆ dibaryon location (see
below), might suggest a possible role for D12 in forming the ∆∆ dibaryon D03 .
A. Gal
Racah Institute of Physics, The Hebrew University, Jerusalem 91904, Israel
E-mail: avragal@savion.huji.ac.il
Shape of the inflaton potential and the efficiency of the universe heating
A.D. Dolgov,1, 2, 3, ∗ A.V. Popov,4, † and A.S. Rudenko1, 5, ‡
1
Novosibirsk State University, Novosibirsk, 630090, Russia
ITEP, Bol. Cheremushkinskaya ul., 25, 113259 Moscow, Russia
3
Dipartimento di Fisica e Scienze della Terra, Universit`
a degli Studi di Ferrara
Polo Scientifico e Tecnologico - Edificio C, Via Saragat 1, 44122 Ferrara, Italy
4
Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk, Moscow, 142190 Russia
5
Budker Institute of Nuclear Physics, Novosibirsk, 630090, Russia
arXiv:1412.0112v1 [astro-ph.CO] 29 Nov 2014
2
It is shown that the efficiency of the universe heating by an inflaton field depends not only on the
possible presence of parametric resonance in production of scalar particles but also strongly depends
on the shape of the oscillations of the inflaton around its equilibrium point. In particular, when
the inflaton oscillations deviate from pure harmonic one towards a succession of step functions,
the production probability rises by several orders of magnitude. This in turn leads to a higher
temperature of the universe after inflaton decay. An example of the inflaton potential, which leads
to such type of the field behavior and sufficiently long inflation, is presented.
I.
INTRODUCTION
The cosmological inflation included, roughly speaking, the following two epochs. The first one was a quasiexponential expansion, when the Hubble parameter, H, slowly changed with time and the universe expanded by
a huge factor, eN where
Z
N = Hdt ≫ 1.
(1.1)
During this period the Hubble parameter exceeded the inflaton mass or, better to say, the condition was fulfilled
2
d U (φ) ≡ |U ′′ (φ)| ,
H 2 > (1.2)
dφ2 where U (φ) is the potential of the inflaton field, φ. Due to the large Hubble friction (see eq. (3.3)) during this
time, the field φ remained almost constant slowly moving in the direction of the ”force” (−U ′ ).
The second stage began when H 2 dropped below |U ′′ | and lasted till the inflaton field reached the equilibrium
value at U ′ (φeq ) = 0. It is usually assumed that φeq = 0 and U (φeq ) = 0 to avoid nonzero vacuum energy. During
this period φ oscillated around φeq producing elementary particles, mostly with masses below the frequency of the
inflaton oscillations. This was a relatively short period which may be called big bang, when the initial vacuum-like
state exploded, creating the primeval cosmological plasma.
The process of the universe heating was first studied in refs. [1–3] within the framework of perturbation theory.
A non-perturbative approach was pioneered in refs. [4, 5]. In both these papers a possibility of excitation of
parametric resonance, which might grossly enhance the particle (boson) production rate was mentioned. In the
model of ref. [4] parametric resonance could not be effectively induced because of the red-shift and scattering of
the produced particles which were dragged out of the resonance zone and the main attention in this work was
dedicated to non-perturbative production of fermions. However, the resonance may be effective if it is sufficiently
wide. In this case the particle production rate can be strongly enhanced [5, 6].
As is well known, parametric resonance exists for bosons only. In quantum language, it can be understood as Bose
amplification of particle production due to presence of identical bosons in the final state, the same phenomena
as the laser induced radiation. For bosons there can be another phenomenon leading to very fast and strong
excitation of the bosonic field coupled to inflaton, if the effective mass squared of such field would be negative
(tachyonic situation). It might naturally happen for sufficiently large and negative product gφ, see below eqs.
(2.1, 2.2). This is the Higgs-like effect, when vacuum state becomes unstable.
Both phenomena are absent in the case of fermion production. Imaginary mass of fermions breaks hermicity
of the Lagrangian, so tachyons must be absent. As for parametric resonance, it is not present in the fermionic
∗ Electronic
address: dolgov@fe.infn.it
address: popov@izmiran.ru
‡ Electronic address: a.s.rudenko@inp.nsk.su
† Electronic
Noname manuscript No.
(will be inserted by the editor)
Fundamental cosmology in the E-ELT era:
The status and future role of tests of fundamental coupling stability
arXiv:1412.0108v1 [astro-ph.CO] 29 Nov 2014
C.J.A.P. Martins
Received: date / Accepted: date
Abstract The observational evidence for the recent acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete—if
not incorrect—and that new physics is out there, waiting to be discovered. The most
fundamental task for the next generation of astrophysical facilities is therefore to
search for, identify and ultimately characterise this new physics. Here we highlight
recent efforts along these lines, mostly focusing on ongoing work by CAUP’s Dark
Side Team aiming to develop some of the science case and optimise observational
strategies for forthcoming facilities. The discussion is centred on tests of the stability
of fundamental couplings (since the provide a direct handle on new physics), but synergies with other probes are also briefly considered. The goal is to show how a new
generation of precision consistency tests of the standard paradigm will soon become
possible.
Keywords Observational cosmology · Fundamental physics · Fundamental
couplings · Dark energy · Astronomical facilities
1 Introduction
In the middle of the XIX century Urbain Le Verrier and others mathematically discovered two new planets by insisting that the observed orbits of Uranus and Mercury
agree with the predictions of Newtonian physics. The first of these—which we now
call Neptune—was soon observed by Johann Galle and Heinrich d’Arrest. However,
the second (dubbed Vulcan) was never found. We now know that the discrepancies
in Mercury’s orbit were a consequence of the fact that Newtonian physics can’t adC.J.A.P. Martins
CAUP and IA-Porto, Rua das Estrelas s/n, 4150-762 Porto, Portugal
Tel.: +351-226089891
Fax: +351-226089831
E-mail: Carlos.Martins@astro.up.pt
Chiral symmetry and effective field theories for
hadronic, nuclear and stellar matter
Jeremy W. Holta , Mannque Rhob,c , Wolfram Weised,e
a Department
of Physics, University of Washington, Seattle, 98195, USA
of Physics, Hanyang University, Seoul 133-791, Korea
c Institut de Physique Th´
eorique, CEA Saclay, 91191 Gif-sur-Yvette, France
d Physik Department, Technische Universit¨
at M¨
unchen, D-85747 Garching, Germany
e ECT ∗ , Villa Tambosi, I-38123 Villazzano (TN), Italy
b Department
arXiv:1411.6681v1 [nucl-th] 24 Nov 2014
Abstract
Chiral symmetry, first entering in nuclear physics in the 1970’s for which Gerry Brown played a seminal role, has led to
a stunningly successful framework for describing strongly-correlated nuclear dynamics both in finite and infinite systems.
We review how the early, germinal idea conceived with the soft-pion theorems in the pre-QCD era has evolved into a
highly predictive theoretical framework for nuclear physics, aptly assessed by Steven Weinberg: “it (chiral effective field
theory) allows one to show in a fairly convincing way that what they (nuclear physicists) have been doing all along
... is the correct first step in a consistent approximation scheme.” Our review recounts both how the theory presently
fares in confronting Nature and how one can understand its extremely intricate workings in terms of the multifaceted
aspects of chiral symmetry, namely, chiral perturbation theory, skyrmions, Landau Fermi-liquid theory, the Cheshire cat
phenomenon, and hidden local and mended symmetries.
Keywords:
Contents
1 Prologue
3
2 Introductory survey
4
2.1
2.2
Low-energy QCD and chiral symmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
2.1.1
Chiral symmetry and the pion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
2.1.2
Pseudoscalar meson spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6
Chiral effective field theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.2.1
The Nambu-Goldstone boson sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.2.2
The baryon sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
2.2.3
Chiral pion-nucleon effective Lagrangian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
3 Chiral symmetry and hadron structure
11
3.1
From little bag to chiral bag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
3.2
Encoding chiral symmetry and confinement in the chiral bag . . . . . . . . . . . . . . . . . . . . . . . . .
12
3.2.1
13
Leakage of baryon charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Preprint submitted to Physics Reports
November 26, 2014
Inflation in R2 supergravity with non-minimal superpotentials
G. A. Diamandis, B. C. Georgalas, K. Kaskavelis,
P. Kouroumalou,, A. B. Lahanas,∗ and G. Pavlopoulos
arXiv:1411.5785v1 [hep-th] 21 Nov 2014
University of Athens, Physics Department, Nuclear and Particle Physics Section, GR–15771 Athens, Greece
We investigate the cosmological inflation in a class of supergravity models that are generalizations
of non-supersymmetric R2 models. Although such models have been extensively studied recently,
especially after the launch of the PLANCK and BICEP2 data, the class of models that can be
constructed has not been exhausted. In this note, working in a supergravity model that is a generalization of Cecotti’s model, we show that the appearance of new superpotential terms, which
are quadratic in the superfield Λ that couples to the Ricci supermultiplet, alters substantially the
form of the scalar potential. The arising potential has the form of the Starobinsky potential times a
factor that is exponential in the inflaton field and dominates for large inflaton values. We show that
the well-known Starobinsky inflation scenario is maintained only for unnaturally small fine-tuned
values of the coupling describing the Λ2 superpotential terms. A welcome feature is the possible
improvement of the tensor to scalar ratio r which however is not of the desired order of magnitude
to agree with the BICEP2 data if all observational constraints are taken into account.
Keywords: Supergravity, Cosmology, Modified Theories of Gravity, Relativity and Gravitation
PACS: 04.65.+e, 98.80.-k, 04.50.Kd, 95.30.Sf
I.
INTRODUCTION
Models of inflation are constrained by recent observations of WMAP [1] and Planck [2] satellites. The
spectral index is found in the range ns = 0.9608 ± 0.0054 while the tensor to scalar ratio is bounded from
above r < 0.111. Moreover the BICEP2 [4] experiment claims discovery of primordial gravitational waves
+0.06
resulting to a ratio r = 0.16−0.05
which, if finally confirmed, is a challenge for both experimentalists and
theorists. PLANCK satellite data [2] are in perfect agreement with the Starobinsky model of inflation [3]
which predicts a tensor to scalar ratio in the range r ' 0.004, which is almost two orders of magnitude
smaller than the claimed discovery of BICEP2 which points towards chaotic inflation [5] .
Much effort has been expended towards building inflationary models embedded in the framework of
supergravity theories. Chaotic inflation [5] scenario can be incorporated in supergravity schemes [6, 7]
and more recently general chaotic inflationary supergravity potentials have been studied [8]. Supergravity
models that incorporate R + R2 terms and reproduce Starobinsky’s inflation predictions for r, ns have
received a lot of attention recently[9–33]. A class of supergravity models are described by no-scale K¨ahler
potentials [34] and many of the proposed inflationary models have a no-scale structure [10, 11, 15, 22,
26, 27, 30, 33]. It is worth noting that in this class of models there is the possibility of accommodating
models interpolating between low ( r ∼ 0.001) and large values ( r ∼ 0.1) depending on the parameters.
This can be also accomplished in attractor solutions that relate in a continuous manner the predictions
of the Starobinsky model with those of the quadratic chaotic potential [35, 36].
Among the possible theoretical schemes, incorporating the virtues of the Starobinsky R2 model that
lead to successful inflation, are higher derivative supergravity Lagrangians [37–39]. In these, besides
the matter chiral and vector multiplets, additional chiral multiplets are unavoidably introduced. In the
minimal scenario [38] one uses two multiplets that after eliminations of the auxiliary fields involved leads
to a supergravity Lagrangian including R2 . This extends the Starobinsky model in a non-trivial manner
∗ Electronic
address: alahanas@phys.uoa.gr
Prepared for submission to JCAP
arXiv:1407.7123v2 [astro-ph.CO] 28 Nov 2014
Parameter estimation with
Sandage-Loeb test
Jia-Jia Geng,a Jing-Fei Zhang,a Xin Zhanga,b,1
a Department
of Physics, College of Sciences, Northeastern University,
Shenyang 110004, China
b Center for High Energy Physics, Peking University,
Beijing 100080, China
E-mail: gengjiajia163@163.com, jfzhang@mail.neu.edu.cn,
zhangxin@mail.neu.edu.cn
Abstract. The Sandage-Loeb (SL) test directly measures the expansion rate of the universe
in the redshift range of 2 . z . 5 by detecting redshift drift in the spectra of Lyman-α forest
of distant quasars. We discuss the impact of the future SL test data on parameter estimation
for the ΛCDM, the wCDM, and the w0 wa CDM models. To avoid the potential inconsistency
with other observational data, we take the best-fitting dark energy model constrained by
the current observations as the fiducial model to produce 30 mock SL test data. The SL
test data provide an important supplement to the other dark energy probes, since they are
extremely helpful in breaking the existing parameter degeneracies. We show that the strong
degeneracy between Ωm and H0 in all the three dark energy models is well broken by the
SL test. Compared to the current combined data of type Ia supernovae, baryon acoustic
oscillation, cosmic microwave background, and Hubble constant, the 30-yr observation of SL
test could improve the constraints on Ωm and H0 by more than 60% for all the three models.
But the SL test can only moderately improve the constraint on the equation of state of dark
energy. We show that a 30-yr observation of SL test could help improve the constraint on
constant w by about 25%, and improve the constraints on w0 and wa by about 20% and
15%, respectively. We also quantify the constraining power of the SL test in the future highprecision joint geometric constraints on dark energy. The mock future supernova and baryon
acoustic oscillation data are simulated based on the space-based project JDEM. We find that
the 30-yr observation of SL test would help improve the measurement precision of Ωm , H0 ,
and wa by more than 70%, 20%, and 60%, respectively, for the w0 wa CDM model.
1
Corresponding author.
Identification of Observables for Quark and Gluon Orbital Angular Momentum
Aurore Courtoy,1, ∗ Gary R. Goldstein,2, † J. Osvaldo Gonzalez Hernandez,3, ‡ Simonetta Liuti,4, § and Abha Rajan5, ¶
arXiv:1412.0647v1 [hep-ph] 1 Dec 2014
1
IFPA, AGO Department, Universit´e de Li`ege, Bˆ
at. B5, Sart Tilman B-4000 Li`ege, Belgium
and nstituto de Fsica, Universidad Nacional Autnoma de Mxico, A.P. 20-364, Mxico 01000, D.F., Mxico.
2
Department of Physics and Astronomy, Tufts University, Medford, MA 02155 USA.
3
Istituto Nazionale di Fisica Nucleare (INFN) - Sezione di Torino via P. Giuria, 1, 10125 Torino, ITALY, Italy
4
University of Virginia - Physics Department, 382 McCormick Rd., Charlottesville, Virginia 22904 - USA
and INFN, Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044, Frascati RM, Italy.
5
University of Virginia - Physics Department, 382 McCormick Rd., Charlottesville, Virginia 22904 - USA
A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular, on its observability, and on its partonic interpretation. Orbital momentum can be defined
in QCD using two different decomposition schemes that yield a kinetic and a canonical definition,
respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist
three generalized parton distributions, and it is therefore more readily observable, while, due to
parity constraints, canonical angular momentum, if defined as suggested in the literature in terms of
generalized transverse momentum distributions, cannot be observed in scattering processes involving
a single hadronic reaction plane.
PACS numbers: 13.60.Hb, 13.40.Gp, 24.85.+p
The question of the observability of Orbital Angular Momentum (OAM) in QCD was recently addressed in Ref.[1].
The main thrust of the paper was to identify an observable from DVCS experiments for OAM as given by the second
moment of the twist-3 GPD, G2 [2, 4]. Alongside with this identification, some difficulties were pointed out which
are inherent with the alternative definition of OAM in terms of Generalized Transverse Momentum Distributions
(GTMDs), concerning especially the way these objects would be measured in deeply virtual exclusive scattering
processes from the proton. This triggered a series of observations in Ref.[5], related to the treatment of parity
transformations in Ref.[1], some of which we believe are ill-founded. This situation, given the important issues at
stake, i.e. the definition of OAM in QCD, and the possibility of measuring it, necessitates therefore an additional
explanation.
The recent discussion follows in the steps of a debate which was initiated previously (see Refs.[6, 7] for reviews) on
the gauge invariant decomposition of the total quark and gluon angular momenta, J q , and J g , into their respective
spin and orbital components. One of the results out of this discussion was that it became clear that OAM could be
defined through a twist three contribution from the relation [2, 3],
Z
Z
Z
Z
1
e q (x, 0, 0) → dx x Gq (x, 0, 0) = −Lq , (1)
− dxx(H q (x, 0, 0) + E q (x, 0, 0)) + dxH
dx x Gq2 (x, 0, 0) =
2
2
where Gq2 is a specific twist three Generalized Parton Distribution (GPD) appearing in the parametrization of the
e2T in the full classification of GPDs given in Ref.[10]);
quark-quark correlation function [2, 4, 8, 9] (G2 was renamed E
q
q
q
e
H , E , and H are the twist two GPDs contributing to the observables for Deeply Virtual Compton Scattering
(DVCS) processes introduced in [11] (see reviews in Refs.[12, 13]. Lq is referred to as kinetic [7] or mechanical [6]
OAM, it appears in the relation [11],
1
1
∆Σ + Lq + J g = ,
2
2
and it is at variance with the canonical OAM, Lq,g
can which is defined through the decomposition [14],
1
1
= ∆Σ + Lqcan + ∆G + Lgcan .
2
2
∗ Electronic
address: aurore.courtoy@ulg.ac.be
address: gary.goldstein@tufts.edu
‡ Electronic address: jog4m@virginia.edu
§ Electronic address: sl4y@virginia.edu
¶ Electronic address: ar5xc@virginia.edu
1 In our previous paper we used the notation L = Lq
q
can .
† Electronic
(2)
1
(3)
MT 2 to the Rescue – Searching for Sleptons in Compressed Spectra at the LHC
Zhenyu Han
Institute for Theoretical Science, University of Oregon, Eugene, OR 97403, USA
Yandong Liu
arXiv:1412.0618v1 [hep-ph] 1 Dec 2014
Department of Physics and State Key Laboratory of Nuclear Physics and Technology,
Peking University, Beijing 100871, China
We propose a novel method for probing sleptons in compressed spectra at hadron colliders.
The process under study is slepton pair production in R-parity conserving supersymmetry,
where the slepton decays to a neutralino LSP of mass close to the slepton mass. In order
to pass the trigger and obtain large missing energy, an energetic mono-jet is required. Both
leptons need to be detected in order to suppress large standard model backgrounds with
one charged lepton. We study variables that can be used to distinguish the signal from the
remaining major backgrounds, which include tt¯, W W +jet, Z+jet, and single top production.
We find that the dilepton mT 2 , bound by the mass difference, can be used as an upper bound
to efficiently reduce the backgrounds. It is estimated that sleptons with masses up to about
150 GeV can be discovered at the 14 TeV LHC with 100 fb−1 integrated luminosity.
1
I.
INTRODUCTION
Low energy supersymmetry (SUSY) is an attractive theory of physics beyond the standard
model (SM). In order to avoid fine tuning to the Higgs mass, super partners of the SM particles are
predicted to be around or below the TeV scale, which is often dubbed “natural supersymmetry”
– see Ref. [1] and references therein. However, SUSY searches at the large hadron collider (LHC)
have not revealed any signal beyond the standard model, which have put stringent constraints on
the SUSY mass spectrum. To reconcile the null results with supersymmetry, one either (partially)
gives up naturalness and accepts that the super particles’ masses are beyond the current reach of
the 8 TeV LHC (which could, however, be discovered at 14 TeV or a future collider), or assumes
SUSY particles are light and accessible, but the signal is hidden in the SM backgrounds. In order
not to miss the SUSY signals, both the two possibilities should be explored. One way to hide light
SUSY particles is to make the spectrum compressed, that is, the mass splittings among the SUSY
particles are so small that the decay products of the SUSY cascades are soft. The signal events
that contain such soft particles, including jets, leptons or photons, are difficult to trigger on, and
even if recorded, they are usually buried in SM backgrounds. Special search strategies are required
to find the signal events and previous studies include those on a light stop [2–5], a light sbottom
[6] and light electroweakinos [7–12]. In this article, we focus on another important SUSY process,
slepton pair production.
We assume the lightest supersymmetric particle (LSP) is a neutralino with mass around 100
GeV. A light slepton with mass close to the LSP mass is not required by naturalness because its
loop contribution to the Higgs mass is small. Nevertheless a 5 ∼ 20 GeV mass splitting, which
we assume in this article, is certainly possible without “fine-tuning” model parameters. Moreover,
such a small splitting is needed to obtain the correct relic density in the co-annihilation scenario
[13]. When sleptons are pair produced and each of which decays to a neutralino, we have two soft
leptons and missing energy in a signal event. The major SM backgrounds include tt¯, W W +jet,
Z(→)τ τ +jet and single top production. In order to pass the trigger, we require an extra hard jet
and large missing energy to be present in the event. This is also the final state particles considered in
Refs. [10, 12], where the discovery potential of the LHC for quasi-degenerate Higgsinos is explored.A
crucial observation in the analysis which makes the discovery possible is the fact that the majority
of the lepton pairs are produced through off-shell Z 0 s in χ02 → χ01 decays, and the dilepton invariant
mass m`` is bound from above by the χ02 − χ01 mass difference. Therefore, we can apply an upper
cut on m`` to eliminate bulk of the background events, while retaining most of the signal events.
This feature is unfortunately absent for slepton pair production because the two leptons necessarily
come from two different decay chains. For a typical 10 GeV lepton pT acceptance cut, the dilepton
invariant mass spreads from ∼ 10 GeV to ∼ 80 GeV, which significantly overlaps with the SM
backgrounds. Clearly, a different strategy is needed.
In this article, we propose a novel method for searching slepton pairs in a compressed spectrum.
In order to exploit the small mass splitting, we consider the mT 2 variable defined from the two
leptons and the missing transverse momentum. This variable, to a good approximation, is bound
by the mass difference between the slepton and the LSP. Because of this property, we use it as an
upper bound in our method. This is in contrast to the traditional use of mT 2 in SUSY searches,
where mT 2 is a variable alternative to the missing transverse momentum and usually used as a lower
Few-Body Systems manuscript No.
(will be inserted by the editor)
V.A. Karmanov · J. Carbonell
arXiv:1412.0590v1 [hep-ph] 1 Dec 2014
Current conservation in electrodisintegration of a
bound system in the Bethe-Salpeter approach
Received: date / Accepted: date
Abstract Using our solutions of the Bethe-Salpeter equation with OBE kernel in Minkowski space
both for the bound and scattering states, we calculate the transition form factors for electrodisintegration of the bound system which determine the electromagnetic current J of this process. Special
emphasis is put on verifying the gauge invariance which should manifest itself in the current conservation. We find that for any value of the momentum transfer q the contributions of the plane wave and
the final state interaction to the quantity J · q cancel each other thus providing J · q = 0. However,
this cancellation is obtained only if the initial Bethe-Salpeter amplitude (bound state), the final one
(scattering state) and the current operator are strictly consistent with each other. A reliable result for
the transition form factor can be found only in this case.
Keywords Bethe-Salpeter equation · Electromagnetic current · Electromagnetic form factors
1 Introduction
Bethe-Salpeter (BS) equation [1] provides an efficient theoretical framework to describe bound and
scattering states of a relativistic system. Finding its solution is complicated by the singularities in
the integrand of the equation as well as by the singular character of the amplitude itself. To avoid
this difficulty, one can perform Wick rotation [2] and transform the BS equation in the Euclidean
form. However, the Wick rotation cannot be performed in the integral for electromagnetic (e.m.) form
factors (see e.g. [3]). Therefore, to calculate form factors, we need the BS solution in Minkowski space.
In finding these solutions, an important progress was achieved in the recent years using different and
independent methods (see [4] for a brief review).
In one of these methods [5] the kernel of the BS equation is approximately represented in a separable form. This allows to perform more advanced analytical calculations and therefore simplifies
finding solutions and form factors. Another method is based on representing the BS amplitude via the
Nakanishi integral [6] both for bound [7; 8; 9; 10; 11] and scattering [12] states. The elastic e.m. form
factor in this method was calculated in [13].
Recently we developed a method [14] based on the direct treatment of singularities of the BS
equation. Both the bound and scattering state amplitudes in Minkowski space were found. They allow
to calculate [15] the electrodisintegration of the bound system, i.e., form factor of the transition: bound
→ scattering state. The contribution of the final state interaction (FSI) to this form factor is given by
V.A. Karmanov
Lebedev Physical Institute, Leninsky Prospekt 53, 119991 Moscow, Russia
E-mail: karmanov@sci.lebedev.ru
J. Carbonell
Institut de Physique Nucl´eaire, Universit´e Paris-Sud, IN2P3-CNRS, 91406 Orsay Cedex, France
Chiral Superfluidity for QCD
T. Kalaydzhyan∗
Department of Physics and Astronomy, Stony Brook University,
Stony Brook, NY 11794-3800, U.S.A.
arXiv:1412.0536v1 [hep-ph] 1 Dec 2014
Abstract
We argue that the strongly coupled quark-gluon plasma formed at LHC and RHIC can
be considered as a chiral superfluid. The “normal” component of the fluid is the thermalized
matter in common sense, while the “superfluid” part consists of long wavelength (chiral)
fermionic states moving independently. We use the bosonization procedure with a finite
cut-off and obtain a dynamical axion-like field out of the chiral fermionic modes. Then we
use relativistic hydrodynamics for macroscopic description of the effective theory obtained
after the bosonization. Finally, solving the hydrodynamic equations in gradient expansion,
we find that in the presence of external electromagnetic fields or rotation the motion of the
“superfluid” component gives rise to the chiral magnetic, chiral vortical, chiral electric and
dipole wave effects. Latter two effects are specific for a two-component fluid, which provides
us with crucial experimental tests of the model.
Introduction
The non-trivial structure of the QCD vacuum attracted much attention in light of recent heavyion experiments performed at RHIC and LHC. These experiments make it possible to study
the strongly-coupled quark-gluon plasma (sQGP) in hadronic scale magnetic fields [1]. The
non-trivial gluonic configurations may induce an imbalance between densities of left- and righthanded light quarks (chirality). As a strong magnetic field is applied to the system, the imbalance can give rise to a net electric current in sQGP along the magnetic field (chiral magnetic
effect [2, 3]). So far it was difficult to build a first-principles theory, describing this and similar
effects, since the physics of sQGP is essentially nonperturbative. However, there is a need in
such a theory, because constant axial chemical potentials, introduced by hand, break unitarity
[4] and lead to various consistency and stability problems [5, 6]. At the same time, without
the knowledge of all possible anomalous effects of a similar kind, one will face difficulties in
the experimental searches for each of them. Fortunately, it seems that such a theory can be
established (and it is sketched below), because QCD contains a long-wave axion-like degree
of freedom, which can play a role of carrier for the chirality. Indeed, one can consider QCD
coupled to QED with an auxiliary gauged UA (1), and bosonize quarks with Dirac eigenvalues
smaller than some fixed scale Λ. Since there is no gauge UA (1) in nature, one can choose a pure
gauge form of the external axial vector field and, as a result of the procedure, one obtains the
∗
e-mail: tigran.kalaydzhyan@stonybrook.edu
1
Prepared for submission to JHEP
arXiv:1412.0520v1 [hep-ph] 1 Dec 2014
Classification of effective operators for interactions
between the Standard Model and dark matter
M. Duch,a B. Grzadkowski
a
b
a
J. Wudkab
Faculty of Physics, University of Warsaw, Ho˙za 69, 00-681 Warsaw, Poland
Department of Physics and Astronomy, UC Riverside,
Riverside, CA 92521, USA
E-mail: mateusz.duch@fuw.edu.pl, bohdan.grzadkowski@fuw.edu.pl,
jose.wudka@ucr.edu
Abstract: We construct a basis for effective operators responsible for interactions between the Standard Model and a dark sector composed of particles with spin ≤ 1. Redundant operators are eliminated using dim-4 equations of motion. We consider simple
scenarios where the dark matter components are stabilized against decay by Z2 symmetries. We determine operators which are loop-generated within an underlying theory and
those that are potentially tree-level generated.
Impact of ηc hadroproduction data on charmonium production and polarization within
NRQCD framework
Hong-Fei Zhang1 , Zhan Sun2 , Wen-Long Sang3 , and Rong Li4
1
arXiv:1412.0508v1 [hep-ph] 1 Dec 2014
3
Department of Physics, School of Biomedical Engineering,
Third Military Medical University, Chongqing 400038, China.
2
Department of Physics, Chongqing University, Chongqing 401331, P.R. China
School of Physical Science and Technology, Southwest University, Chongqing 400700, China
4
Department of Applied Physics, Xi’an Jiaotong University, Xi’an 710049, China
(Dated: December 2, 2014)
With the recent LHCb data on ηc production and based on heavy quark spin symmetry, we obtain
the long-distance matrix elements for both ηc and J/ψ productions, among which, the color-singlet
one for ηc is obtained directly by the fit of experiment for the first time. Using our long-distance
matrix elements, we can provide good description of the ηc and J/ψ hadroproduction measurements.
Our predictions on J/ψ polarization are in good agreement with the LHCb data and pass through
the two sets of CDF measurements in medium pt region. Considering all the possible uncertainties
carefully, we obtained quite narrow bands of the J/ψ polarization curves.
PACS numbers: 12.38.Bx, 12.39.St, 13.85.Ni, 14.40.Pq
Nonrelativistic QCD (NRQCD) factorization framework [1] has gained its reputation from the success
in many processes, among which, heavy quarkonia
hadroproduction [2–4] is one of the most remarkable
examples. Moreover, several groups have accomplished
their computer programs for the calculation of QCD corrections to quarkonium related processes. QCD next-toleading order (NLO) predictions [5–10] based on NRQCD
achieved good agreement with almost all the experimental measurements on quarkonia hadroproduction. However, for the J/ψ case, one is still suffering from the
ambiguity caused by the freedom in the determination
of the color-octet (CO) long-distance matrix elements
(LDMEs) [5–7, 10–13]. In addition, the J/ψ polarization puzzle is another challenge that NRQCD is facing.
Despite that three groups [11–13] have made great efforts to proceed the calculation to NLO in αs , none
of their CO LDMEs can reproduce the recent LHCb
data [14, 15] with good precision. On the other hand,
many works [3, 4, 16, 17] have proceeded their concerns to the processes in which no experimental data
can be used to extract the LDMEs. There, they estimate these LDMEs based on heavy quark spin symmetry
(HQSS) and velocity scaling rule (VSR). Nevertheless,
the proof of NRQCD factorization does not require the
two rules [18, 19], hence, the phenomenological test of
them is urgent.
Recently, LHCb data [20] on ηc produciton came out
and provided an opportunity to further investigate these
problems. Ref. [21, 22] studied direct ηc hadroproduction
at leading order (LO) in αs within NRQCD framework,
[8]
however, missing the 1 S0 channel. Since only inclusive
and prompt ηc production rate has been measured, one
should also consider contributions from hc feeddown, the
asymptotic behavior of which, in large transverse momentum (pt ) limit, scales as p−6
t . According to our previous work [17], the contribution of this part is negligible
comparing with experimental data. Feeddown contribu-
tions from other excited c¯
c bound states are even smaller
than that from hc , so that they are not under our consideration. For direct ηc production, up to the order of
v 4 , where v is the typical relative velocity of the constituent quark and antiquark in the quarkonium, four
[1]
[8]
[8]
[8]
channels (1 S0 , 1 S0 , 3 S1 , 1 P1 ) are involved. Among
[8]
them, 3 S1 channel scales as p−4
in large pt limit, while
t
the other three scale as p−6
.
Moreover,
the NLO QCD
t
corrections to all the channels are not significant, which
indicates good convergence in αs expansion. Therefore,
[8]
it is possible to determine hOηc (3 S1 )i precisely by the
fit of the experimental data. Further, we can assume
HQSS and fix the other two CO LDMEs for ηc produciton as well as those for J/ψ production, and see
whether they are able to provide reasonable descriptions
of J/ψ production and polarization. Noticing that, in
Ref. [6, 12, 13], the LDMEs obtained by minimizing χ2
do not indicate the VSR, we give up employing this rule
as the basis of our arguement.
We should also notice that the values of the produc[1]
[1]
tion LDMEs hOηc (1 S0 )i and hOJ/ψ (3 S1 )i have never
been obtained directly from the fit of experiment; only
the values of the decay ones have been extracted from
experiment. The production LDMEs are considered to
be the same as the decay ones in the sense of VSR, the
importance of the higher order effects of which is not
clear. Since the absolute values of the CS LDMEs play
a very important role in the exclusive double charmonia
production in e+ e− collisions, high-precision determination of them would be urgent. LHCb data on ηc production rate provides an opportunity to obtain the value of
[1]
hOηc (1 S0 )i by fitting experimental data. As a result,
precise evaluation of the short-distance coefficient (SDC)
[1]
of 1 S0 channel is necessary, and our calculation will be
accurate to NLO in αs as well as in v 2 , while, higher
order corrections are neglected. We should also consider
the uncertainty caused by the possible large logarithmic
arXiv:1412.0503v1 [hep-ph] 1 Dec 2014
Heavy flavours in high-energy nuclear collisions:
quenching, flow and correlations
A. Beraudo† , A. De Pace, M. Monteno, M. Nardi, F. Prino
INFN, sezione di Torino, Via Pietro Giuria 1, I-10125 Torino
E-mail: † beraudo@to.infn.it
Abstract. We present results for the quenching, elliptic flow and azimuthal correlations
of heavy flavour particles in high-energy nucleus-nucleus collisions obtained through the
POWLANG transport setup, developed in the past to study the propagation of heavy quarks
in the Quark-Gluon Plasma and here extended to include a modeling of their hadronization in
the presence of a medium. Hadronization is described as occurring via the fragmentation of
strings with endpoints given by the heavy (anti-)quark Q(Q) and a thermal parton q(q) from
the medium. The flow of the light quarks is shown to affect significantly the RAA and v2 of the
final D mesons, leading to a better agreement with the experimental data.
Heavy quarks – indirectly accessible through D-mesons, heavy-flavour decay electrons and
muons and J/ψ’s from B decays – have been used for a long time as probes of the medium
formed in heavy-ion collisions. In a series of papers [1, 2, 3] over the last few years we developed
a complete setup (referred to as POWLANG) for the study of heavy flavour observables in highenergy nucleus-nucleus collisions, describing the initial hard production of the QQ pairs and the
corresponding parton-shower stage through the POWHEG-BOX package [4, 5] and addressing
the successive evolution in the plasma through the relativistic Langevin equation. Here we
present a brief summary of our recent efforts aimed at supplementing the above numerical tool
by modeling the hadronization of the heavy quarks accounting for the presence of a surrounding
medium made of light thermal partons feeling the collective flow of the fluid: a comprehensive
exposition can be found in [6].
In order to simulate the hadronization of heavy quarks in the medium at the end of their
propagation in the QGP we proceed as follows. Once a heavy quark Q, during its stochastic
propagation in the fireball, has reached a fluid cell below the decoupling temperature Tdec ,
it is forced to hadronize. One extracts then a light antiquark q light (up, down or strange,
with relative thermal abundances dictated by the ratio m/Tdec ) from a thermal momentum
distribution corresponding to the temperature Tdec in the Local Rest Frame (LRF) of the fluid;
information on the local fluid four-velocity uµfluid provided by hydrodynamics allows one to boost
the momentum of q light from the LRF to the laboratory frame. A string is then constructed
joining the endpoints given by Q and q light and is then passed to PYTHIA 6.4 [7] to simulate its
fragmentation into hadrons (and their final decays). In agreement with PYTHIA, in evaluating
their momentum distribution, light quarks are taken as “dressed” particles with the effective
masses mu/d = 0.33 GeV and ms = 0.5 GeV. Concerning Tdec the values 0.155 and 0.17 GeV
are explored. In the following some representative results obtained with the new hadronization
procedure are displayed and compared to experimental data (when available).
EPJ Web of Conferences will be set by the publisher
DOI: will be set by the publisher
c Owned by the authors, published by EDP Sciences, 2014
Possible Implication of a Single Nonextensive pT Distribution for Hadron Production in High-Energy pp Collisions ⋆
Cheuk-Yin Wong1 , a , Grzegorz Wilk2 , b , Leonardo J. L. Cirto3 , c , Constantino Tsallis2,4 , d
arXiv:1412.0474v1 [hep-ph] 1 Dec 2014
1
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
National Centre for Nuclear Research, Warsaw 00-681, Poland
3
Centro Brasileiro de Pesquisas Fisicas & National Institute of Science and Technology for Complex Systems,
Rua Xavier Sigaud 150, 22290-180 Rio de Janeiro-RJ, Brazil
4
Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA
2
Abstract. Multiparticle production processes in pp collisions at the central rapidity region are usually considered to be divided into independent "soft" and "hard" components. The first is described by exponential
(thermal-like) transverse momentum spectra in the low-pT region with a scale parameter T associated with
the temperature of the hadronizing system. The second is governed by a power-like distributions of transverse
momenta with power index n at high-pT associated with the hard scattering between partons. We show that the
hard-scattering integral can be approximated as a nonextensive distribution of a quasi-power-law containing a
scale parameter T and a power index n = 1/(q−1), where q is the nonextensivity parameter. We demonstrate that
the whole region of transverse momenta presently measurable at LHC experiments at central rapidity (in which
the observed cross sections varies by 14 orders of magnitude down to the low pT region) can be adequately
described by a single nonextensive distribution. These results suggest the dominance of the hard-scattering
hadron-production process and the approximate validity of a “no-hair" statistical-mechanical description of the
pT spectra for the whole pT region at central rapidity for pp collisions at high-energies.
1 Introduction
Particle production in pp collisions comprises of many
different mechanisms in different parts of the phase space.
We shall be interested in particle production in the central
rapidity region where it is customary to divide the multiparticle production into independent soft and hard processes populating different parts of the transverse momentum space separated by a momentum scale p0 . As a rule
of thumb, the spectra of the soft processes in the low-pT
region are (almost) exponential, F(pT )∼exp(−pT /T ), and
are usually associated with the thermodynamical description of the hadronizing system, the fragmentation of a flux
tube with a transverse dimension, or the production of particles by the Schwinger mechanism [1–5]. The pT spectra
of the hard process in the high-pT region are regarded as
essentially power-like, F(pT )∼p−n
T , and are usually associated with the hard scattering process [6–10]. However,
it was found already long time ago that both description
could be replaced by simple interpolating formula [11],
!−n
pT
F(pT ) = A 1 +
,
(1)
p0
⋆ Presented by G.Wilk
a e-mail: wongc@ornl.gov
b e-mail: wilk@fuw.edu.pl
c e-mail: cirto@cbpf.br
d e-mail: tsallis@cbpf.br
that becomes power-like for high pT and exponential-like
for low pT . Notice that for high pT , where we are usually
neglecting the constant term, the scale parameter p0 becomes irrelevant, whereas for low pT it becomes, together
with power index n, an effective temperature T = p0 /n.
The same formula re-emerged later to become known as
the QCD-based Hagedorn formula [12]. It was used for
the first time in the analysis of UA1 experimental data [13]
and it became one of the standard phenomenological formulas for pT data analysis.
In the mean time it was realized that Eq. (1) is just another realization of the nonextensive distribution [14] with
parameters q and T , and a normalization constant A,
pT 1/(1−q)
F (pT ) = A 1 − (1 − q)
,
T
(2)
that has been widely used in many other branches of
physics. For our purposes, both formulas are equivalent
with the identification of n = 1/(q−1) and p0 = nT , and we
shall use them interchangeably. Because Eq. (2) describes
nonextensive systems in statistical mechanics, the parameter q is usually called the nonextensivity parameter. As
one can see, Eq. (2) becomes the usual Boltzmann-Gibbs
exponential distribution for q → 1, with T becoming the
temperature. Both Eqs. (1) and (2) have been widely used
Nuclear
Physics A
Nuclear Physics A 00 (2014) 1–8
arXiv:1412.0471v1 [hep-ph] 1 Dec 2014
Initial state in relativistic nuclear collisions
and Color Glass Condensate
Fran¸cois Gelis
Institut de Physique Th´eorique, CEA/Saclay, 91191 Gif sur Yvette cedex, France
Abstract
In this talk, I discuss recent works related to the pre-hydrodynamical stages of ultra-relativistic heavy ion collisions.
Keywords: Heavy Ion Collisions, Color Glass Condensate, Initial State
1. Introduction
Hydrodynamical models are very successful at reproducing bulk observables in high energy heavy ion collisions.
However, it is a long standing puzzle to understand from the underlying Quantum Chromodynamics (QCD) why
this description is so effective. Indeed, the description of the early stages of heavy ion collisions which is most
closely related to QCD –the Color Glass Condensate (CGC) framework– predicts at the very beginning of the fireball
evolution a situation which is very different from a quasi perfect fluid.
The purpose of this talk is to discuss recent works aiming at a first principles CGC description of the early stages
of heavy ion collisions, where by “early stages” we mean the pre-hydrodynamical evolution (left part of fig. 1).
Ultimately, the goal is to have a description of these early stages that explains how the hydrodynamical behavior
develops and that matches smoothly into hydrodynamics (right part of fig. 1), in such a way that the time τ0 at which
the switching happens becomes unessential (in the same spirit as a factorization scale for parton distributions). Note
PL / PT
t
+1
freeze out
Pre-Hydro
hadrons
kinetic theory
gluons & quarks in eq.
time
viscous hydro
τ0
gluons & quarks out of eq.
strong fields
classical dynamics
Hydro
z
-1
Figure 1. Left: stages of a heavy ion collision. Right: matching to hydrodynamics.
1
Calibrating Analytical Models for Semilocal Strings
arXiv:1412.0432v1 [hep-ph] 1 Dec 2014
A. Lopez-Eiguren1
Department of Theoretical Physics, University of the Basque Country UPV-EHU, 48040
Bilbao, Spain
E-mail: asier.lopez@ehu.es
Abstract. In this work we calibrate two different analytic models of semilocal strings by
constraining the values of their free parameters. In order to do so, we use data obtained from
the largest and most accurate field theory simulations of semilocal strings to date, and compare
several key properties with the predictions of the models. As this is still work in progress, we
present some preliminary results together with descriptions of the methodology we are using in
the characterisation of semilocal string networks.
1. Introduction
Understanding the evolution of string networks is crucial for predicting their number densities,
which in turn determine their potentially observable effects. However, the quantitatively
accurate modelling of string network evolution is a difficult problem, requiring the combination
of a range of techniques (both numerical and analytical), and interpolating between physics at
very different energy scales.
Here, we present a calibration of analytical models for semilocal strings using field theory
simulations. This work is part of an ongoing project where we tackle in turn different aspects
of the calibration procedure by comparing the numerical simulations with predictions for the
analytic models. Firstly, in section 3, we study the large-scale properties of the simulated
networks [1]. Then, in section 4, we outline the comparison between field theory simulations
and the analytic models, anticipating work that will appear in [2]. Section 5 shows the last
ingredient of our analysis, where we present the techniques we will use in a future work [3] to
estimate the velocities of the semilocal strings. Prior to all this, in section 2 we introduce the
semilocal model and the analytic models used in this work, as well as the numerical simulations
performed.
2. The Model
2.1. Semilocal Model
Semilocal strings [5, 6, 7] were introduced as a minimal extension of the Abelian Higgs (AH)
model with two complex scalar fields instead of just one, that form an SU (2) doublet. This leads
to U (1) flux-tube solutions even though the vacuum manifold is simply connected. The strings
of this extended model have some similarities with ordinary local U (1) strings, but they are not
purely topological and will therefore have different properties. For example, since they are not
1
Work in collaboration with A.Ach´
ucarro, A.Avgoustidis, A.M.M.Leite, C.J.A.P.Martins, A.S.Nunes, J.Urrestilla
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–6
Radiative corrections to Higgs coupling constants in two Higgs doublet models
Mariko Kikuchi∗
arXiv:1412.0375v1 [hep-ph] 1 Dec 2014
Department of Physics, University of Toyama, 3190 Gofuku, Toyama 930-8555, JAPAN
Abstract
A pattern of deviations in the Standard Model (SM) like Higgs boson (h) couplings from their SM predictions
depends on the structure of the Higgs sector and the Yukawa interaction. In particular, in Two Higgs Doublet Models
(THDMs) with a softly-broken Z2 symmetry, different characteristic patterns of deviation in Yukawa coupling constants (h f f¯) can be allowed depending on four types of Yukawa interactions. We calculate h f f¯ coupling constants at
the one-loop level in all the types of THDMs. Even if there is no deviation in the h f f¯ couplings at the tree level, they
can deviate from the SM predictions by a few percent due to extra Higgs boson loop contributions. We find that if the
deviations in the gauge couplings hVV (V = Z, W) are found with an enough large to be measured at the International
Linear Collider (ILC), the scale factors for the h f f¯ couplings do not overlap among the THDMs with four types of
Yukawa interactions even taking into account the radiative corrections. Therefore, in such a case, we can indirectly
determine the type of the THDMs at the ILC even without information from direct searches of the additional Higgs
bosons.
Keywords: Extended Higgs sectors, Radiative corrections
1. Introduction
Although the standard model (SM) like Higgs boson
(h) was discovered at the LHC experiment [2, 3], a lot of
things are still unknown in the Higgs sector: e.g., what
is the origin of negative mass term in the SM Higgs potential, whether the Higgs field is an elementary field or
a composite field. Furthermore, we have not yet understood the shape of the Higgs sector. The minimal Higgs
sector of the SM is just an assumption. There is no principle that only one isospin doublet field must be present.
There are possibilities that the Higgs sector is extended,
and all extended Higgs sectors have not excluded at all
by the data of the LHC. On the other hand, we can say
that the structure of the Higgs sector is strongly related
to a scenario of the new physics beyond the SM, because
a lot of models based on those scenarios introduce extended the Higgs sectors. Determining the structure of
∗ This talk is based on the collaboration with Shinya Kanemura and
Kei Yagyu [1]
the Higgs sector by bottom up approach is one of the
most effective procedure to establish the new physics.
In this talk, we consider a possibility to reconstruct
the shape of the Higgs sector by coupling measurements
of the SM like Higgs boson at future collider experiments. In general, in extended Higgs models, coupling
constants of the SM like Higgs boson h deviate from
the predictions in the SM due to two kinds of effects.
One is the effect of field mixing. The other is the loop
effect due to the extra Higgs bosons. A pattern of deviations in Higgs couplings depend on the number of the
Higgs field, their representations and the mass of Higgs
bosons in the loop. It is possible to discriminate extended Higgs sectors by using future precision data and
comprehensively evaluating all coupling constants of h
in each model.
Within the
√ relatively large uncertainties in the current
LHC data ( s = 7, 8 TeV, the integrated luminosity (L)
is about 25 fb−1 ), measured Higgs couplings seem to be
consistent with the SM at both ATLAS
√ [2] and CMS [3].
At the high luminosity LHC with s = 14 TeV and
Baryon and lepton number violating effective operators in a
non-universal extension of the Standard Model
J. Fuentes-Martín
arXiv:1412.0370v1 [hep-ph] 1 Dec 2014
Instituto de Física Corpuscular, CSIC - Universitat de València,
Apt. Correus 22085, E-46071 València, Spain
Abstract. It is well known that non-abelian Yang-Mills theories present non-trivial minima of the action, the so-called
instantons. In the context of electroweak theories these instanton solutions may induce violations of baryon and lepton number
of the form ∆B = ∆L = n f , with n f being the number of families coupled to the gauge group. An interesting feature of
these violations is that the flavor structure of the gauge couplings is inherited by the instanton transitions. This effect is
generally neglected in the literature. We will show that the inclusion of flavor interactions in the instanton solutions may
be interesting in certain theoretical frameworks and will provide an approach to include these effects. In particular we will
perform this implementation in the non-universal SU(2)l ⊗ SU(2)h ⊗U(1)Y model that singularizes the third family. Within
this framework, we will use the instanton transitions to set a bound on the SU(2)h gauge coupling.
Keywords: Baryon Number Violation, Lepton Number Violation, Non-perturbative effects
PACS: 11.30.Fs, 11.30.Hv, 12.60.Cn
INTRODUCTION
It has been known for some time that baryon (B) and lepton (L) numbers are violated in the electroweak sector
of the Standard Model (SM) due to anomalies [1, 2]. This violation takes place in such a way that, at lowest
order, ∆B = ∆L = n f with n f the number of families coupled to the gauge group and therefore the quantity B − L
remains conserved. ’t Hooft realized that the explicit violation of these global symmetries is due to classical gauge
configurations with non-trivial topological charge [3, 4]. These gauge configurations are termed instantons and
describe tunneling transitions between different inequivalent vacua. At zero temperature thepotential barrier that
separate the different vacua has a huge height, which gives rise to a suppression factor O exp −8π 2 /g2 for these
B + L violating processes. It has been suggested that B + L violating processes might be unsuppressed in high-energy
collisions [5] where the vacuum transitions, denoted now sphalerons, take place from above the potential barrier
and therefore are free of the exponential suppression. The computation of these processes was done in Refs. [6, 7].
Unfortunately, the calculations performed in this direction violate the unitarity bound and therefore are unreliable.
Even though the SM is in perfect agreement with the current experimental data, several theoretical and experimental
issues need to be addressed. They have been extensively treated in the literature giving rise to many theories Beyond
the Standard Model (BSM). Although low-energy instanton transitions are highly suppressed in the SM model this
might no longer be true for BSM theories where the gauge couplings are larger. This possibility was explored in
the framework of gauge non-universal models in Ref. [8] where the inclusion of flavor dynamics was missing in the
calculation. This talk follows closely the work done in Ref. [9] and is devoted to the introduction of inter-family
mixing in the one-instanton transitions. We will show that these effects are crucial in the calculation of proton decay
observables and will present a systematic approach to its inclusion in the model. Once that the instanton-mediated
baryon and lepton number violating amplitudes have been calculated, we will obtain an effective Lagrangian for these
interactions that violates not only baryon and lepton number but also flavor. These operators will be used in order to
constrain the gauge couplings from proton decay. For the sake of concreteness, we will perform this calculation in the
non-universal SU(2)l ⊗ SU(2)h ⊗U(1)Y model. However, many of the results presented here can be easily applied to
other new physics models.
Non-sterile electroweak-scale right-handed neutrinos and the dual nature of the
126-GeV scalar
Vinh Hoang,1, ∗ Pham Q. Hung,1, 2, † and Ajinkya Shrish Kamat1, ‡
1
arXiv:1412.0343v1 [hep-ph] 1 Dec 2014
2
Department of Physics, University of Virginia, Charlottesville, VA 22904-4714, USA
Center for Theoretical and Computational Physics, Hue University College of Education, Hue, Vietnam
(Dated: December 2, 2014)
Can, and under which conditions, the 126-GeV SM-like scalar with the signal strengths for its decays into W + W − , ZZ, γγ, b¯b and τ τ¯ being consistent with the SM predictions be accommodated in
models that go beyond the Standard Model? Is it truly what it appears to be? A minimal extension
of the original electroweak-scale right-handed neutrino model, in which right-handed neutrinos naturally obtain electroweak-scale masses, shows a scalar spectrum which includes the 126-GeV SM-like
scalar possessing signal strengths compatible with experiment but also a dual nature quite unlike
that of the Standard Model. In other words, the 126-GeV SM-like scalar could be an impostor.
I.
INTRODUCTION
The discovery of the 126-GeV SM-like scalar [1] and
the present absence of any new physics signals has opened
up a whole host of questions as to the true nature of the
electroweak symmetry breaking and to what may lie beyond the Standard Model. The sole existence of the 126GeV particle would leave unanswered several deep questions such as the origin of neutrino masses, the hierarchy
of quark and lepton masses among many others. It also
implies that the electroweak vacuum is metastable with
drastic consequences in the very far-distant future [2]. It
remains to be seen whether this most simple picture- albeit one with many question marks- will be the ultimate
theory of nature or it is merely an effective theory at
current accessible energies whose reality tests are incomplete and more non-SM phenomena will pop up in the
not-too-distant future with Run II of the LHC.
Despite the present lack of new physics at the LHC,
it does not imply that it is not there. On the contrary,
new physics has already appeared in the neutrino sector
through neutrino oscillation and its implication on neutrino masses. This evidence, although quite clear, is only
indirect and does not show where the new physics that
gives rise to the aforementioned phenomena may appear.
This difficulty in finding a direct evidence for the new
physics involved in generating neutrino masses is compounded by the fact that these masses are so tiny, more
than seven orders of magnitude smaller than the light-
∗
†
‡
vvh9ux@virginia.edu
pqh@virginia.edu
ask4db@virginia.edu
est lepton: the electron. In the most generic scenario of
the elegant seesaw mechanism for generating tiny masses,
the right-handed neutrinos are sterile i.e. singlets under
the electroweak gauge group. In a nutshell, the two mass
eigenvalues are m2D /M and M where the Dirac mass mD
is proportional to the electroweak scale while the Majorana mass M is mD . In addition to the fact that νR ’s
are assumed to be electroweak singlets, the very large values for M in a generic scenario makes it very very difficult
to probe the crucial physics, namely that which gives rise
to M which is responsible for the lightness of the “active”
neutrinos. Another facet of this new physics is the Majorana nature of the “active” neutrinos themselves which
could manifest itself through neutrino less double beta
decays which so far have not been observed. Through
neutrino oscillations, we have a hint of new physics but
what it might be and where to look for it is still a big
mystery at the present time.
The aforementioned uncertainties rest in large part
on the assumption that right-handed neutrinos are electroweak singlets. This usually comes from a certain
extension of the SM such as the Left-Right symmetric
model SU (2)L × SU (2)R × U (1)B−L [3] or the Grand
Unified model SO(10), among others. It goes without
saying that the singlet assumption is not verified in the
absence of experimental signals of right-handed neutrinos. If one is however willing to entertain the idea that
right-handed neutrinos are not sterile, there is an entire
panorama of accessible phenomena that can be searched
for and studied. A non-sterile right-handed neutrino necessarily interacts with the electroweak gauge bosons and
the Majorana mass term is expected to carry the electroweak quantum number and hence is proportional to
The chiral magnetic effect in heavy-ion collisions
from event-by-event anomalous hydrodynamics
Yuji Hirono,1, ∗ Tetsufumi Hirano,2 and Dmitri E. Kharzeev1, 3
1
Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA
2
Department of Physics, Sophia University, Tokyo 102-8554, Japan
3
Department of Physics, Brookhaven National Laboratory, Upton, New York 11973-5000, USA
(Dated: December 2, 2014)
The (3+1)D relativistic hydrodynamics with chiral anomaly is used to obtain a quantitative
description of the chiral magnetic effect (CME) in heavy-ion collisions. We find that the chargedependent hadron azimuthal correlations are sensitive to the CME, and that the experimental
observations are consistent with the presence of the effect.
arXiv:1412.0311v1 [hep-ph] 1 Dec 2014
PACS numbers:
The experimental study of charge-dependent hadron
azimuthal correlations in heavy-ion collisions at RHIC
[1, 2] and LHC [3] revealed a signal qualitatively consistent with the separation of electric charge predicted
[4] as a signature of local P- and CP-odd fluctuations in
QCD matter. The subsequent studies [5–7] improved the
theoretical understanding of the underlying phenomenon
– the separation of electric charge in the quark-gluon
plasma induced by the chirality imbalance in the presence
of background magnetic field, or the “chiral magnetic effect” (CME), see Ref. [8] for a review and additional references. The existence of CME has been confirmed in
first-principle lattice QCD×QED simulations [9–12]. By
holographic methods, the CME has also been found to
persist at strong coupling [13], in accord with its nondissipative, topologically protected nature.
Because the macroscopic behavior of matter at strong
coupling is described by hydrodynamics, it is natural
to address the question of the existence of CME within
the framework of fluid dynamics. Son and Surowka [14]
showed that the CME indeed is an integral part of relativistic hydrodynamics, and moreover its strength as
fixed by the second law of thermodynamics is consistent
with the field-theoretical prediction. The CME current
in the hydrodynamic regime is carried by a novel collective gapless excitation, the chiral magnetic wave [15, 16].
Conformal anomalous hydrodynamics at second order in
the derivative expansion has been formulated in [17].
Relativistic hydrodynamics with fluctuating initial
conditions proved very successful in explaining the bulk
of RHIC and LHC data (see Refs. [18–20] for recent
reviews). It is thus appropriate to rely on this approach also for describing the CME in heavy-ion collisions, by using hydrodynamics with the terms induced
by chiral anomaly and magnetic fields – so-called anomalous hydrodynamics, or chiral magnetohydrodynamics
(CMHD). The first pilot numerical study of anomalous
hydrodynamics was performed in Ref. [21], where the
effects of anomaly on the charge-dependent elliptic flow
were investigated. Nevertheless, a fully quantitative description of the experimental data on charge-dependent
azimuthal correlations has not been performed until now.
In this Letter, we perform such a study basing on threedimensional ideal CMHD with event-by-event fluctuations in the initial conditions.
Let us first describe the measured experimental observable [22] sensitive to the CME that we aim to describe.
The azimuthal-angle distribution of observed particles
reads
dN α
∝ 1 + 2v1α cos(φ − ΨRP ) + 2aα
1 sin(φ − ΨRP )
dφ
X
(1)
+
2vnα cos n(φ − Ψn ),
n>1
where α ∈ {+, −}. The Fourier coefficients vn± of the
azimuthal-angle distribution characterize the shape of
the produced matter in momentum space. The component with n = 1 is called the directed flow. In Eq. (1), we
decomposed the directed flow into two directions, along
FIG. 1: Schematic picture of a heavy-ion collision event in
the transverse plane. B indicates the magnetic field, and J
is the electric current induced by the chiral magnetic effect in
the case of a positive initial axial charge density. The direction
of J is flipped if the initial axial charge is negative.
Next-to-leading Order Calculation for Jets Defined
arXiv:1412.0298v1 [hep-ph] 30 Nov 2014
by a Maximized Jet Function
Tom Kaufmann a , Asmita Mukherjee b , Werner Vogelsang a
a
Institute for Theoretical Physics, T¨
ubingen University, Auf der Morgenstelle 14,
72076 T¨
ubingen, Germany
b
Department of Physics, Indian Institute of Technology Bombay,
Powai, Mumbai 400076, India
Abstract
We present a next-to-leading order QCD calculation for the single-inclusive production of collimated jets at hadron colliders, when the jet is defined by maximizing a suitable jet function
that depends on the momenta of final-state particles in the event. A jet algorithm of this type
was initially proposed by Georgi and subsequently further developed into the class of “JET algorithms”. Our calculation establishes the infrared safety of the algorithms at this perturbative
order. We derive analytical results for the relevant partonic cross sections. We discuss similarities
and differences with respect to jets defined by cone or (anti-)kt algorithms and present numerical
results for the Tevatron and the LHC.
Jet quenching in pp and pA collisions
∗
B.G. Zakharov1
arXiv:1412.0295v1 [hep-ph] 30 Nov 2014
1
L.D. Landau Institute for Theoretical Physics, GSP-1, 117940, Kosygina Str. 2, 117334 Moscow, Russia
We study jet quenching in pp and pA collisions in the scenario with formation of a mini quark-gluon
plasma. We find a significant suppression effect. For light hadrons at pT √
∼ 10 GeV we obtained the
reduction of the spectra by ∼ [20−30, 25−35, 30−40]% in pp collisions at s = [0.2, 2.76, 7] TeV. We
discuss how jet quenching in pp collisions may change the predictions for the nuclear modification
factors in AA collisions for light and heavy flavors. We also give predictions for modification of the
photon-tagged and inclusive jet fragmentation functions in high multiplicity pp events.
PACS numbers:
I.
INTRODUCTION
One of the manifestation of the quark-gluon plasma (QGP) formation in AA collisions is the jet quenching phenomenon which is dominated by the radiative parton energy loss [1–7]. It leads to suppression of
the high-pT spectra, which is characterized by the nuclear modification factor RAA given by the ratio of
the inclusive cross section for AA collisions to the binary-scaled inclusive cross section for pp collisions
RAA =
dσ(AA → hX)/dpT dy
.
Nbin dσ(pp → hX)/dpT dy
(1)
It would be extremely interesting to observe jet quenching in pp and pA collisions, since it would be a
direct signal of the mini-QGP formation. The QGP formation in pp and pA collisions have been addressed
in several publications recently [8–10] from the viewpoint of the hydrodynamical flow effects. In recent
papers [11, 12] we studied the possible manifestations of jet quenching in pp collisions within the lightcone path integral approach [3], which we previously used for analysis of jet quenching in AA collisions
[13–16]. In [11] we discussed the medium modification of the γ-tagged fragmentation functions (FFs)
and in [12] the medium modification factor Rpp and its effect on the nuclear modification factors RAA
and RpA . The medium modification factor Rpp characterizes the difference between the real inclusive pp
cross section, accounting for the final-state jet interaction in the QGP, and the perturbative one, i.e.,
dσ(pp → hX)/dpT dy = Rpp dσpert (pp → hX)/dpT dy .
(2)
Since we cannot switch off the final state interaction in the QGP, the Rpp is not an observable quantity.
Nevertheless, it may affect the theoretical predictions for RAA . Indeed, in the scenario with the QGP
formation in pp collisions one should use in the denominator in (1) the real inclusive pp cross section
which differs from the perturbative one. In this case one should compare with experimental RAA the
following quantity:
st
RAA = RAA
/Rpp ,
(3)
st
where RAA
is the standard nuclear modification factor calculated using the pQCD predictions for the
particle spectrum in pp collisions. The effect of the Rpp may be important for the centrality dependence
of RAA and the azimuthal anisotropy (simply because in the scenario with the QGP formation in pp
collisions αs becomes bigger). It should also be important for the jet flavor tomography of the QGP [15–
18]. Because the effect of Rpp on RAA for heavy quarks should be smaller due to weaker jet quenching
for heavy quarks in pp collisions. In this talk I review the results of [11, 12] and extend the analysis [12]
to heavy flavors.
∗
Talk at XIth Quark Confinement and the Hadron Spectrum, Saint-Petersburg, Russia, 8-12 September 2014.
Prepared for submission to JHEP
arXiv:1412.0258v1 [hep-ph] 30 Nov 2014
The Higgs Portal Above Threshold
Nathaniel Craig,a Hou Keong Lou,b Matthew McCullough,c and Arun Thalapillild
a
Department of Physics, University of California, Santa Barbara, CA 93106, USA
Department of Physics, Princeton University, Princeton, NJ 08540, USA
c
Theory Division, CERN, 1211 Geneva 23, Switzerland
d
Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA
b
E-mail: ncraig@physics.ucsb.edu, hlou@princeton.edu,
matthew.mccullough@cern.ch, thalapillil@physics.rutgers.edu
Abstract: The discovery of the Higgs boson opens the door to new physics interacting via
the Higgs Portal, including motivated scenarios relating to baryogenesis, dark matter, and
electroweak naturalness. We systematically explore the collider signatures of singlet scalars
produced via the Higgs Portal at the 14 TeV LHC and a prospective 100 TeV hadron collider.
We focus on the challenging regime where the scalars are too heavy to be produced in the
decays of an on-shell Higgs boson, and instead are produced primarily via an off-shell Higgs.
Assuming these scalars escape the detector, promising channels include missing energy in
association with vector boson fusion, monojets, and top pairs. We forecast the sensitivity of
√
searches in these channels at s = 14 & 100 TeV and compare collider reach to the motivated
parameter space of singlet-assisted electroweak baryogenesis, Higgs Portal dark matter, and
neutral naturalness.
ArXiv ePrint: 14xx.xxxx
Average gluon and quark jet multiplicities
A.V. Kotikov
arXiv:1412.0224v1 [hep-ph] 30 Nov 2014
Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
Abstract. We show the results in [1, 2] for computing the QCD contributions to the scale evolution of average gluon and quark
jet multiplicities. The new results came due a recent progress in timelike small-x resummation obtained in the MS factorization
scheme. They depend on two nonperturbative parameters with clear and simple physical interpretations. A global fit of these
two quantities to all available experimental data sets demonstrates by its goodness how our results solve a longstandig problem
(5)
of QCD. Including all the available theoretical input within our approach, αs (Mz ) = 0.1199 ± 0.0026 has been obtained in
the MS scheme in an approximation equivalent to next-to-next-to-leading order enhanced by the resummations of ln x terms
through the NNLL level and of ln Q2 terms by the renormalization group. This result is in excellent agreement with the present
world average.
Keywords: Gluon and quark multiplicities, evolution, diagonalization
PACS: 12.38.Cy, 12.39.St, 13.66.Bc, 13.87.Fh
INTRODUCTION
Collisions of particles and nuclei at high energies usually produce many hadrons and their production is a typical
process where nonperturbative phenomena are involved. However, for particular observables, this problem can be
avoided. In particular, the counting of hadrons in a jet that is initiated at a certain scale Q belongs to this class of
observables. In this case, one can adopt with quite high accuracy the hypothesis of Local Parton-Hadron Duality
(LPHD), which simply states that parton distributions are renormalized in the hadronization process without changing
their shapes [3]. Hence, if the scale Q is large enough, this would in principle allow perturbative QCD to be
predictive without the need to consider phenomenological models of hadronization. Nevertheless, such processes
are dominated by soft-gluon emissions, and it is a well-known fact that, in such kinematic regions of phase space,
fixed-order perturbation theory fails, rendering the usage of resummation techniques indispensable. As we shall
see, the computation of avarage jet multiplicities indeed requires small-x resummation, as was already realized a
long time ago [4]. In Ref. [4], it was shown that the singularities for x ∼ 0, which are encoded in large logarithms
of the kind 1/x lnk (1/x), spoil perturbation theory, and also render integral observables in x ill-defined, disappear
after resummation. Usually, resummation includes the singularities from all orders according to a certain logarithmic
accuracy, for which it restores perturbation theory.
Small-x resummation has recently been carried out for timelike splitting fuctions in the MS factorization scheme,
which is generally preferable to other schemes, yielding fully analytic expressions. In a first step, the next-to-leadinglogarithmic (NLL) level of accuracy has been reached [5, 6]. In a second step, this has been pushed to the next-to-nextto-leading-logarithmic (NNLL), and partially even to the next-to-next-to-next-to-leading-logarithmic (N3 LL), level
[7]. Thanks to these results, we were able in [1, 2] to analytically compute the NNLL contributions to the evolutions
of the average gluon and quark jet multiplicities with normalization
factors evaluated to next-to-leading (NLO) and
√
approximately to next-to-next-to-next-to-order (N3 LO) in the αs expansion. The previous literature contains a NLL
result on the small-x resummation of timelike splitting fuctions obtained in a massive-gluon scheme. Unfortunately,
this is unsuitable for the combination with available fixed-order corrections, which are routinely evaluated in the MS
scheme. A general discussion of the scheme choice and dependence in this context may be found in Refs. [8].
The average gluon and quark jet multiplicities, which we denote as hnh (Q2 )ig and hnh (Q2 )iq , respectively, represent
the average numbers of hadrons in a jet initiated by a gluon or a quark at scale Q. In the past, analytic predictions were
obtained by solving the equations for the generating functionals in the modified leading-logarithmic approximation
√
3/2
(MLLA) in Ref. [9] through N3 LO in the expansion parameter αs , i.e. through O(αs ). However, the theoretical
prediction for the ratio r(Q2 ) = hnh (Q2 )ig /hnh (Q2 )iq given in Ref. [9] is about 10% higher than the experimental
data at the scale of the Z 0 boson, and the difference with the data becomes even larger at lower scales, although the
perturbative series seems to converge very well. An alternative approach was proposed in Ref. [10], where a differential
No-go for tree level R-symmetry breaking
Feihu Liua, * , Muyang Liub, † and Zheng Sunb, c ‡
arXiv:1412.0183v1 [hep-ph] 30 Nov 2014
a
School of Physical Electronics, University of Electronic Science and Technology of China,
Chengdu 610054, P. R. China
b
Center for Theoretical Physics, College of Physical Science and Technology,
Sichuan University, Chengdu 610064, P. R. China
c
State Key Laboratory of Theoretical Physics and Kavli Institute for Theoretical Physics China (KITPC),
Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China
E-mail: * liufeihu04@gmail.com, † liumuyang14@hotmail.com, ‡ sun ctp@scu.edu.cn
Abstract
We show that in gauge mediation models with tree level R-symmetry breaking where supersymmetry and Rsymmetries are broken by different fields, the gaugino mass either vanishes or finds contribution from loop level Rsymmetry breaking. Thus tree-level R-symmetry breaking is either no-go or redundant for phenomenology model
building.
1
Introduction
Supersymmetry (SUSY) [1] provides a natural solution to several unsolved problems in the Standard Model (SM), such
as the gauge hierarchy problem, gauge coupling unification and dark matter candidates. Since supersymmetric particles (sparticles) have not been discovered yet, SUSY must be broken to give them heavy masses escaping the current
experimental limit. To avoid light sparticles in the supersymmetric standard model (SSM), SUSY must be broken in a
hidden sector, and then the SUSY breaking effects are mediated to the observable SSM sector by a messenger sector,
giving sparticle mass spectrum and coupling constants which may be examined at the LHC or other future experiments.
There are three competitive mediation mechanisms: gravity mediation, gauge mediation, and anomaly mediation. We are
focusing on gauge mediation models [2, 3, 4] in this work.
Following the discussion of the Nelson-Seiberg theorem [5, 6, 7], R-symmetries are required to build a generic SUSY
breaking model. From phenomenology point of view, the R-symmetry needs to be broken spontaneously in order to allow
for the gaugino mass. The R-symmetry is usually broken by the SUSY breaking pseudomodulus [8, 9, 10, 11] which gets
a vacuum expectation value (VEV) at loop level through the Coleman-Weinberg potential [12], or through the inclusion
of D-terms [13, 14]. There are also models with tree level R-symmetry breaking from tree level VEVs of fields other than
the pseudomodulus [15, 16]. These models usually involve many fields with specific R-charges, and the gaugino mass is
often generated from multiple VEVs of fields at both loop level and tree level in such complicated models [17]. A wide
class of tree-level SUSY and R-symmetry breaking models with classically stable pseudomoduli spaces have been shown to
give zero gaugino masses at one loop level [18, 19]. Nevertheness, it still remains unclear whether in principle the gaugino
mass could be generated from tree level R-symmetry breaking.
In gauge mediation models, the SUSY breaking fields are coupled to messengers which are charged under the SM gauge
symmetry. SUSY breaking is mediated to the SSM sector through gauge interactions, and soft terms such as the gaugino
mass emerge at low energy. For loop level R-symmetry breaking, the SUSY breaking pseudomodulus field X also breaks
the R-symmetry at loop level. It has the VEV
X = hXi + θ2 FX .
(1)
The resulting gaugino mass is
Mg˜ ∼
α FX
.
4π hXi
(2)
For a tree level R-symmetry breaking model, we have two fields which breaks SUSY and R-Symmetry respectively. They
have VEVs
X = θ2 FX , Y = hY i.
(3)
1
Large-Nc Regge spectroscopy∗
arXiv:1412.0124v1 [hep-ph] 29 Nov 2014
Wojciech Broniowski
Institute of Physics, Jan Kochanowski University, 25-406 Kielce, Poland
The H. Niewodnicza´
nski Institute of Nuclear Physics, Polish Academy of
Sciences, PL-31342 Cracow, Poland
Enrique Ruiz Arriola
Departamento de F´ısica At´
omica, Molecular y Nuclear and Instituto Carlos I de
F´ısica Te´
orica y Computacional, Universidad de Granada, E-18071 Granada,
Spain
Pere Masjuan
PRISMA Cluster of Excellence, Institut f¨
ur Kernphysik, Johannes
Gutenberg-Universt¨at, Mainz D-55099, Germany
This talk, dedicated to Eef van Beveren on the occasion of his birthday,
reviews some of our results concerning the hadron spectroscopy, Regge
trajectories, and the large-Nc meson-dominance of hadronic form factors.
PACS numbers: 12.38.Lg, 11.30, 12.38.-t
The presentation is based on several of our recent papers [1–5] devoted
to hadron spectroscopy involving the large-Nc arguments and Regge trajectories. We begin with a brief review of the old Hagedorn [6] idea, applied to
the fundamental question of understanding the spectrum of QCD, as well
as its applications to thermodynamic properties which find practical use in
understanding the lattice data and modeling the relativistic heavy-ion collisions. The excitation function of QCD is presented in Fig. 1, where we plot
the density of states (left panel) represented via the Breit-Wigner functions
(for plotting purposes the stable states were attributed some finite width),
as well as the cumulative number of states with mass below m. We include
∗
Talk presented by WB at EEF70, Workshop on Unquenched Hadron Spectroscopy:
Non-Perturbative Models and Methods of QCD vs. Experiment, Coimbra, Portugal,
1-5 September 2014
(1)
An underlying symmetry determines all elements of CKM and
PMNS up to a universal constant?
1
2
Hong-Wei Ke1∗ and Xue-Qian Li2†
School of Science, Tianjin University, Tianjin 300072, China
School of Physics, Nankai University, Tianjin 300071, China
arXiv:1412.0116v1 [hep-ph] 29 Nov 2014
Abstract
Observing the CKM matrix elements written in different parametrization schemes, one can notice
obvious relations among the sine-values of the CP phases in those schemes. Using the relations,
we establish a few parametrization-independent equations, by which the matrix elements of the
CKM matrix can be completely fixed up to a universal parameter. If it is true, we expect that
there should exist a hidden symmetry in the nature which determines the relations. Moreover, it
requires a universal parameter, naturally it would be the famous Jarlskog invariant which is also
parametrization independent. Thus the four parameters (three mixing angles and one CP phase)
of the CKM matrix are not free, but determined by the symmetry and the universal parameter. As
we generalize the rules to the PMNS matrix for neutrino mixing, the CP phase of the lepton sector
is predicted to be within a range of 0 ∼ 59◦ centered at 39◦ (in the Pa parametrization) which will
be tested in the future experiments.
PACS numbers: 12.15.Ff, 14.60.Pq, 12.15.Hh
∗
†
khw020056@hotmail.com
lixq@nankai.edu.cn
1
Complete One-Loop Corrections to e+ e− → χ˜01 χ˜01 h0 for Different
Scenarios
1
S. M. Seif1 , T.A. Azim1
Faculty of Science, Physics Department, Cairo University, Giza, Egypt.
(Dated: November 20, 2014)
arXiv:1412.0109v1 [hep-ph] 29 Nov 2014
Abstract
In the present work, the full one-loop corrections to the production of a light neutral minimal supersymmetric
standard model Higgs boson (h0 ) with a pair of lightest neutralinos (χ
˜01 ) in e+ e− collisions within the Minimal
Supersymmetric Standard Model (MSSM) are presented. The details of the renormalization scheme used are
presented. Our results also include the QED corrections as well as the weak corrections. It is found that
the contribution from the weak and QED corrections is significant and needs to be taken into account in the
future linear collider experiments. Numerical results for two different SUSY scenarios —Higgsino and Gaugino
scenarios— for e+ e− → χ
˜01 χ
˜01 h0 are given.
PACS numbers:
1
Introduction
fields. If supersymmetry is realized in nature, neutralinos should be found in the next generation of high enOne of the main goals of the Tevatron and the LHC ex- ergy experiments at Tevatron, LHC [6] and a future e+ e−
perimental programs was to detect a Higgs boson. On collider. Especially at a linear e+ e− collider, it will be
the 4th of July 2012, the CMS and the ATLAS exper- possible to perform measurements with high precision
imental teams at the LHC, announced independently, [7, 8].
that they both discovered a previously unknown boson
of mass between 125 and 127 GeV [1, 2, 3], whose beIn view of the experimental prospects, it is inevitable
havior so far is "consistent with" a Higgs boson, and it
is confirmed likely, on March 2013, to be a Higgs boson, to include higher–order terms in the calculation of the
although yet it is unclear which model best supports the measured quantities in order to achieve theoretical preparticle or whether multiple Higgs bosons exist. This dictions matching the experimental accuracy. Former
discovery has impact on the search for particles such as studies on char- gino–pair production [9, 10, 11] and
neutralino [4]. Supersymmetry (SUSY) is a novel space- scalar–quark decays [12] have revealed that the Born–
time symmetry between bosons and fermions. In realistic level predictions can be influenced significantly by one–
models, SUSY is broken at the weak scale implying that loop radiative corrections.
all Standard Model (SM) particles must have superpartners with masses in the range ∼ 100 – 1000 GeV that will
be accessible to colliders. In the Minimal Supersymmetric Standard Model (MSSM), there are as many as five
Higgs mass states: two scalars, h 0 and H 0 , a pseudo
scalar, A0 and a pair of charged bosons, H ± , which
makes the experimental search more involved. The couplings of the Higgs bosons to the SUSY scalar fermions
f˜ to the charginos χ
˜± and neutralinos χ
˜0 depend on the
soft–SUSY breaking parameters and therefore carry information on the fundamental SUSY theory.
Since the mass of neutralinos are among the precision observables with lots of information on the SUSYbreaking structure, the relations between the particle
masses and the SUSY parameters are important theoretical quantities for precision calculations. In (MSSM)
˜04 , which are the fermion
[5], one has four neutralinos χ
˜01 -χ
mass eigenstates of the supersymmetric partners of the
photon, the Z 0 boson, and the neutral Higgs bosons H01,2 .
Their mass matrix depends on the parameters M1 , M2 ,
µ, and tan β, where M1 and M2 the SU(2) and U(1)
gauge mass parameter, tan β = v1 /v2 with v1,2 the vacuum expectation values of the two neutral Higgs doublet
In this paper, we use on-shell renormalization scheme
in the loop calculations of the Higgs and neutralino
sectors of the CP-conserving MSSM. The calculation
was performed using the FeynArts and FormCalc computer packages. All the renormalization constants, required to determine the various counterterms for the
Higgs, neutralino and other sectors, being implemented
in the MSSM version of FeynArts [13] for completion at
the one-loop level. The resulting amplitudes were algebraically simplified using FormCalc and then converted
to a FORTRAN program. The LoopTools package was
used to evaluate the one-loop scalar and tensor integrals
[14].
The paper is arranged as follows: The analytical calculations of the Born cross section to the e+ e− → χ
˜01 χ
˜01 h0
process is given in section 2, where some numerical results are shown. The virtual, the electroweak, and the
soft photonic corrections are studied in section 3. The
numerical results are presented in section 4. Finally, the
conclusions are given in section 5.
1
EPJ Web of Conferences will be set by the publisher
DOI: will be set by the publisher
c Owned by the authors, published by EDP Sciences, 2014
QCD prediction of jet structure in 2D trigger-associated momentum correlations and implications for multiple parton interactions
Thomas A. Trainor1
arXiv:1412.0082v1 [hep-ph] 29 Nov 2014
1
CENPA 354290 University of Washington, Seattle, Washington, USA
Abstract. The expression “multiple parton interactions” (MPI) denotes a conjectured QCD mechanism representing contributions from secondary (semi)hard parton scattering to the transverse azimuth region (TR) of
jet-triggered p-p collisions. MPI is an object of underlying-event (UE) studies that consider variation of TR
nch or pt yields relative to a trigger condition (leading hadron or jet pt ). An alternative approach is 2D triggerassociated (TA) correlations on hadron transverse momentum pt or rapidity yt in which all hadrons from all p-p
events are included. Based on a two-component (soft+hard) model (TCM) of TA correlations a jet-related TA
hard component is isolated. Contributions to the hard component from the triggered dijet and from secondary
dijets (MPI) can be distinguished, including their azimuth dependence relative to the trigger direction. Measured e+ -e− and p- p¯ fragmentation functions and a minimum-bias jet spectrum from 200 GeV p- p¯ collisions are
convoluted to predict the 2D hard component of TA correlations as a function of p-p collision multiplicity. The
agreement between QCD predictions and TA correlation data is quantitative, confirming a dijet interpretation
for the TCM hard component. The TA azimuth dependence is inconsistent with conventional UE assumptions.
1 Introduction
In a high-energy physics (HEP) context dijet production
has long been accepted as an important mechanism for
hadron formation by parton fragmentation [1–3]. But
in a heavy-ion context “freezeout” from a flowing bulk
medium is assumed to be the nearly-exclusive hadron production mechanism [4–6], and there are claims that bulkmedium collectivity may even play a role in p-p, p-A and
d-A systems [7]. Previously-accepted contributions from
minimum-bias (MB) dijets to high energy collisions are
displaced by the claimed presence of strong collective motion (flows) in a thermalized bulk medium or quark-gluon
plasma to explain spectrum and correlation structure.
Such claims are based in part on the a priori assumption that all hadrons with transverse momentum pt < 2
GeV/c emerge from a thermalized bulk medium [8]. But
that interval includes more than 90% of minimum-bias
(MB) jet fragments, according to jet measurements and
QCD predictions [9–12]. Analysis of spectra and correlations does appear to confirm a dominant role for dijet
production at low pt in all collision systems [10, 12–17].
But we can further extend the QCD description of MB dijet manifestations at low pt , at least in p-p collisions.
In previous studies a jet-related hard component was
isolated from the pt spectrum of 200 GeV p-p collisions by means of its charge multiplicity nch dependence,
leading to a two-component (soft+hard) spectrum model
(TCM) [15]. The spectrum hard component for p-p spectra has been described quantitatively by a pQCD calculation [12] based on a MB jet (hard-scattered parton) spec-
trum [18] and measured parton fragmentation functions
(FFs) [9]. Those results establish that the spectrum and
angular-correlation hard components in p-p collisions are
jet related [10, 12],
The present study extends that program with a method
to predict 2D trigger-associated (TA) hadron correlations
arising from dijets produced in high-energy p-p collisions
based on measured FFs and a large-angle-scattered parton spectrum [19–21]. Identification of unique triggereddijet contributions to TA correlations in p-p collisions may
then probe the phenomenon of multiple parton interactions
(MPI) and test claims of bulk collectivity in p-A, d-A and
heavy ion (A-A) collisions at the Relativistic Heavy-Ion
Collider (RHIC) and the Large Hadron Collider (LHC).
In this paper we define 2D trigger-associated (TA) correlations, derive a TA two-component model (TCM) and
extract a TA hard component (HC) that may represent dijet
fragments. We then derive a system to predict the TA HC
via a measured MB jet spectrum and parton FFs. Comparisons with measured TA hard components serve to identify
kinematic limits on dijet formation in p-p collisions. We
isolate triggered dijets from secondary dijets (MPI) and
test underlying-event (UE) assumptions.
2 p-p spectra and dijet production
The TCM for 2D TA correlations is based on the TCM for
1D yt spectra from p-p collisions which we briefly summarize here. The p-p spectrum TCM is derived from the
nch dependence of pt or transverse rapidity yt ≡ ln[(mt +
pt )/mπ ] spectra. A “soft” component S (yt ) with fixed
Femtoscopic Signature of Strong Radial Flow
in High-multiplicity pp Collisions
Yuji Hirono∗ and Edward Shuryak
Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA
(Dated: December 2, 2014)
arXiv:1412.0063v1 [hep-ph] 29 Nov 2014
Hydrodynamic simulations are used to calculate the identical pion HBT radii, as a function of the
pair momentum kT . This dependence is sensitive to the magnitude of the collective radial flow in the
transverse plane, and thus comparison to ALICE data enables us to derive its magnitude. By using
hydro solutions with variable initial parameters we conclude that in this case fireball explosions
starts with a very small initial size, well below 1 fm.
I.
INTRODUCTION
The so called Hanbury-Brown-Twiss (HBT) interferometry method originally came from radio astronomy [1]
as intensity interferometry. The influence of Bose symmetrization of the wave function of the observed mesons
in particle physics was first emphasized by Goldhaber et
al. [2] and applied to proton-antiproton annihilation. Its
use for the determination of the size/duration of the particle production processes had been proposed by Kopylov and Podgoretsky [3] and one of us [4]. Heavy-ion
collisions, with its large multiplicities, turned the “femtoscopy” technique into a large industry. Early applications for RHIC heavy-ion collisions were in certain tension with the hydrodynamical models, but this issue was
later resolved, see e.g. [5]. The development of the HBT
method had made it possible to detect the magnitude
and even deformations of the flow.
Makhlin and Sinyukov [6] made the important observation that HBT radii are sensitive to collective flows of the
matter. The radii decrease with the increase of the total
transverse momentum kT = (p1T + p2T )/2 of the pair.
A sketch shown in Fig.1 provides a qualitative explanation to this effect: the larger is kT , the brighter becomes a
small (shaded) part of the fireball, which the radial flow is
maximal and the its direction coincides with the direction
of kT . This follows from maximization of the Dopplerblue-shifted thermal spectrum ∼ exp (−pµ uµ /Tf ). In this
paper we will rely on this effect, as well as on ALICE
HBT data, to deduce the magnitude of the flow in high
multiplicity pp collisions.
(Although we will not use those, let us also mention
that the HBT method can also be used not only for determination of the radial flow, but for elliptic flow as well:
see e.g. early STAR measurements [7]. Another development in the HBT field was a shift from two-particle
to three-particle correlations [8], [9] available due to very
high multiplicity of events as well as high luminosities of
RHIC and LHC colliders.)
With the advent of LHC it became possible to trigger
on high multiplicity events, both in pp and pP b collisions:
∗ Electronic
address: yuji.hirono@stonybrook.edu
k1
kt
v
k2
FIG. 1: (Color online)Sketch of how the radial flow (arrows
directed radially from the fireball center) influences the HBT
radii. At small kT the whole fireball (the circle) is visible,
but at larger kT one sees only the part co-moving in the same
direction – shown by shaded ellipse.
the resulting sample revealed angular anisotropies v2 , v3
similar to anisotropic flows in heavy-ion (AA) collisions.
At the moment the issue whether those can or cannot be
described hydrodynamically is under debate. So far the
discussion of the strength of the radial flow was based
on the spectra of identified particles, see [12, 13]. In this
paper we look at the radial flow from a different angle,
using the measured HBT radii [10].
The HBT radii for pp collisions at LHC has been measured by the ALICE collaboration [10], as a function
of multiplicity. Their magnitude has been compared to
those coming from hydro modelling in Refs. [21, 22]. Our
analysis of the HBT radii focus on the strength of the radial flow. We illustrate how the radii, and especially the
ratio Ro /Rs , are indicative of the flow magnitude.
While at minimally biased collisions and small multiplicities the observed HBT radii are basically independent of the pair transverse momentum kT , for high multiplicity the observed radii decrease with kT . So, the
effect we are after appears only at the highest multiplicities – the same ones which display hydro-like angular correlations and modifications of the particle spectra.
The strongest decrease, as expected, is seen for the so
called Ro radius, for which this reduction in the interval
kT = 0.1 · · · 0.7 GeV reaches about factor 4 in magnitude.
The kT dependence of the HBT radii tells us about
the strength of the flow. The reason these data are quite
important is the following: the HBT radii at small kT
Modified ππ amplitude with σ pole
P. Bydˇzovsk´
ya , R. Kami´
nskib , V. Nazarib
ˇ z/Prague 25068, Czech Republic
Nuclear Physics Institute, ASCR, Reˇ
Institute of Nuclear Physics, Polish Academy of Sciences, Krak´
ow 31-342, Poland
a
arXiv:1412.0013v1 [hep-ph] 28 Nov 2014
b
A set of well known once subtracted dispersion relations with imposed crossing symmetry condi¯ and ηη) and P (ππ, ρ2π, and ρσ) wave
tion is used to modify unitary multichannel S (ππ, K K,
amplitudes mostly below 1 GeV. Before the modifications, these amplitudes significantly did not
satisfy the crossing symmetry condition and did not describe the ππ threshold region. Moreover,
the pole of the S wave amplitude related with the f0 (500) meson (former f0 (600) or σ) had much
smaller imaginary part and bigger real one in comparison with those in the newest Particle Data
Group Tables. Here, these amplitudes are supplemented by near threshold expansion polynomials
and refitted to the experimental data in the effective two pion mass from the threshold to 1.8 GeV
and to the dispersion relations up to 1.1 GeV. In result the self consistent, i.e. unitary and fulfilling
the crossing symmetry condition, S and P wave amplitudes are formed and the σ pole becomes
much narrower and lighter. To eliminate doubts about the uniqueness of the so obtained sigma pole
position short and purely mathematical proof of the uniqueness of the results is also presented. This
analysis is addressed to a wide group of physicists and aims at providing a very effective and easy
method of modification of, many presently used, ππ amplitudes with a heavy and broad σ meson
without changing of their original mathematical structure.
PACS numbers: 11.55.Fv,11.55.-m,11.80.Et,13.75.Lb
I.
INTRODUCTION
New once-subtracted dispersion relations with the imposed crossing symmetry condition for the S-F wave ππ
amplitudes have recently been derived and presented in
the Refs. [1, 2]. Further analysis of these equations in
the Ref. [3] for the S and P waves (the so-called GKPY
equations) led inter alia to very precise determination of
the position of the pole related with the f0 (500) resonance (hereafter σ).
Importance and effectiveness of similar dispersion relations but with two subtractions, i.e. of the so-called Roy
equations [4], were already presented on the example of
the elimination of long standing up-down ambiguity in
the ππ S wave amplitude below 1 GeV [5, 6] and of determination of the quark condensate constants [7].
Quite recently the Roy’s equations were once again
effectively exploited in searching for unique determination of the S and P wave ππ scattering amplitudes [8–
10]. Due to incorporation of two boundary conditions for
these amplitudes, it was possible to find such analytical
solution below 800 MeV in accordance with derived and
proven theorem on the uniqueness of such solutions [11].
One of the byproduct of these analyses and those with
GKPY equations [1, 3] was official and long-awaited significant modification of the position of the σ pole in Particle Data Tables. For many years this state was appearing with mass and width noticeably larger than 500 MeV.
For example in the Particle Data Tables in 2010 [12] the
mass was in the range M = 400–1200 MeV and the full
width Γ = 600–1000 MeV. Before year 1994 the σ meson
was even excluded from the Tables for about 20 years.
Since 2012 its parameters are much better determined,
i.e., M = 400–550 MeV and Γ = 400–700 MeV [13].
The reason for this many years of confusion and uncer-
tainty about these parameters was that their determination was based mostly on fairly disparate and uncertain
experimental results. Fortunately, well-grounded theoretical works based on dispersion relations with the imposed crossing symmetry condition, presented, e.g. in
[1, 3, 8–10], provided very strong arguments to resolve
the existing uncertainties.
Despite of those big and widely accepted changes in
parameters of the σ meson many analyses can still use the
old, i.e. significantly too wide and too massive, scalarisoscalar state below 1 GeV. The reason for this may
be difficulties in changing parameters of some models or
parametrizations to adapt them to the new requirements.
Use of the correct and precise parametrizations of the
ππ amplitudes is, however, sometimes crucial especially
when high precision of the final results is required. This
can be particularly well seen, for example, in analyses
of the ππ final state interactions in the heavy mesons
decays (e.g. B or D → M ππ where M is K or π) needed
to determine parameters of a very small CP violation.
Another kind of analyses which need correct and very
precise ππ amplitudes are those which pretend to describe spectrum of light mesons decaying into ππ pairs
in given partial waves and which strongly require verification of compliance with the crossing symmetry condition.
¯ and ηη) analOne of them is the multichannel (ππ, K K,
ysis of the ππ scattering data presented in [14–16] which
uses unitary amplitudes up to 1.8 GeV with proper analytical properties on the whole Riemann surface. However, in the construction of these amplitudes the crossing
symmetry condition was not required what resulted in
insufficiently precise description of the ππ elastic region.
Moreover, these amplitudes did not describe correctly the
experimental data in the vicinity of the ππ threshold.
The aim of this work is to present a general method of
On the microscopic nature of the photon strength function
O. Achakovskiy and A. Avdeenkov
Institute for Physics and Power Engineering, 249033 Obninsk, Russia
S. Goriely
Institut d’Astronomie et d’Astrophysique, ULB, CP 226, B-1050 Brussels, Belgium
S. Kamerdzhiev∗
Institute for Nuclear Power Engineering NRNU MEPHI, 249040 Obninsk, Russia
arXiv:1412.0268v1 [nucl-th] 30 Nov 2014
S. Krewald
Institut f¨
ur Kernphysik, Forschungszentrum J¨
ulich, D-52425 J¨
ulich, Germany
The pygmy dipole resonances and photon strength functions in stable and unstable Ni and Sn
isotopes are calculated within the microscopic self-consistent version of the extended theory of finite
fermi systems which includes phonon coupling effects. The Skyrme forces SLy4 is used. A pygmy
dipole resonance in 72 Ni is predicted at the mean energy of 12.4 MeV exhausting 25% of the total
energy-weighted sum rule. The microscopically obtained photon E1 strength functions are used
to calculate nuclear reaction properties. For the first time, average radiative widths and radiative
neutron capture cross sections have been calculated taking the phonon coupling into account as
well as the uncertainties caused by various microscopic level density models. In all three quantities
considered, the contribution of phonon coupling turned out to be significant and is found necessary
to explain available experimental data.
PACS numbers: 24.10.-i, 24.60.Dr, 24.30.Cz, 21.60.Jz
Recently, Photon Strength Functions (PSF) for Snisotopes below the neutron separation threshold have
been determined using the (3 He,3 He’γ) and (3 He,αγ) reactions [1] (and references therein). Commonly, one parameterizes the PSF phenomenologically using, for example, generalized Lorentzian models [2, 3]. The Sn data
obtained in Ref.[1] show some extra strength near 8 MeV,
which cannot be described by the traditional smooth
phenomenological parameterizations. Such an additional
strength is interpreted as a pygmy dipole resonance
(PDR). Pygmy resonances exhausts typically about 1-2%
of the Energy Weighted Sum Rule (EWSR) but, nevertheless, significantly increases the radiative neutron capture cross section and may affect the nucleosynthesis of
neutron-rich nuclei by the r-process [4]. In neutron-rich
nuclei, for example, 68 Ni [5] and, probably, 72 Ni, 74 Ni, the
EWSR fraction is much larger. Note that for nuclei with
small neutron separation energy, less than typically 3–4
MeV, the PDR properties are changed significantly [4],
and therefore, phenomenological systematics obtained by
fitting characteristics of stable nuclei cannot be applied.
Given the importance of PSF both in astrophysics [4]
and nuclear engineering [6], microscopic investigations
are required, especially when extrapolations to exotic
nuclei are needed. Mean-field approaches using effective nucleon interactions, such as the Hartree-Fock Bogoliubov method and the quasi-particle random-phase
approximation (HFB+QRPA) [4], allow systematic self-
∗ kaev@obninsk.com
consistent studies of isotope chains, and indeed have been
included in modern nuclear reaction codes like EMPIRE
[7] and TALYS [8]. Such an approach is of higher predictive power in comparison with phenomenological models.
However, as we discuss below and as confirmed by recent
experiments, the HFB+QRPA approach is necessary but
not sufficient. To be exact, it should be complemented
by the effect describing the interaction of single-particle
degrees of freedom with the low-lying collective phonon
degrees of freedom, known as the phonon coupling (PC).
The experiments in the PDR energy region [1, 9, 10]
have given additional information about the PDR and
PSF structures. The PSF structures at 8-9 MeV in six
Sn isotopes obtained by the Oslo method [1] could not
be explained within both the standard phenomenological
approach [1] and the microscopic HFB+QRPA approach
[10]. In both cases, to explain the experiment, it was
necessary to add ”by hand” some additional strength of
about 1–2% of the EWSR. The results [10] directly confirm the necessity to go beyond the HFB+QRPA method.
In particular, the PC effects discussed in Refs.[11–13]1
may be at the origin of such an extra strength.
In this work, we use the self-consistent version of the
extended theory of finite fermi systems (ETFFS) [11] in
1
There are misprints in the English version of Ref.[13]: in all
figure captions and in the discussions of the corresponding results
there must stand QTBA instead of RQTBA, i.e. all calculations
in Ref.[13] have been performed within the ETFFS(QTBA), or
simply QTBA, (not RQTBA !).
Activation cross sections of α-particle induced nuclear reactions on hafnium and
deuteron induced nuclear reaction on tantalum: production of 178 W/178m Ta
generator
F. T´ark´anyia , S. Tak´acsa , F. Ditr´oia,∗, A. Hermanneb , A.V. Ignatyukd , M.S. Uddinc
arXiv:1412.0411v1 [nucl-ex] 1 Dec 2014
a Institute
for Nuclear Research, Hungarian Academy of Sciences (ATOMKI), Debrecen, Hungary
b Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels, Belgium
c Cyclotron Radioisotope Center (CYRIC), Tohoku University, Sendai, Japan
d Institute of Physics and Power Engineering (IPPE), Obninsk, Russia
Abstract
In the frame of a systematic study of charged particle production routes of medically relevant radionuclei, the excitation function for indirect production of 178m Ta through nat Hf(α,xn)178−178m Ta nuclear reaction was measured for the
first time up to 40 MeV. In parallel, the side reactions nat Hf(α,x)179,177,176,175 W, 183,182,178g,177,176,175 Ta, 179m,177m,175 Hf
were also assessed. Stacked foil irradiation technique and γ-ray spectrometry were used. New experimental cross
section data for the nat Ta(d,xn)178 W reaction are also reported up to 40 MeV. The measured excitation functions are
compared with the results of the ALICE-IPPE, and EMPIRE nuclear reaction model codes and with the TALYS 1.4
based data in the TENDL-2013 library. The thick target yields were deduced and compared with yields of other
charged particle ((p,4n), (d,5n) and (3 He,x)) production routes for 178 W.
Keywords: hafnium and tantalum target, α-irradiation, deuteron irradiation, hafnium, tantalum and tungsten
radioisotopes, physical yield, 178 W production
1. Introduction
The short-lived (9.3 min) metastable state of the 178 Ta
a radioisotope can be used both for diagnostic (PET
studies, total β+ decay: 1.24%) as well as for therapeutic purposes (Kα1 + Kα 2 60%) (Lacy et al., 2001;
Layne and Lacy, 1990; Nichols, 2013; Wilson et al.,
1987). It can be produced from long-lived (21.7 d) 178 W
via a 178 W/178 Ta generator. The used production routes
include proton and deuteron induced reactions on tantalum and alpha and 3 He particle induced reactions on
hafnium. In the frame of a coordinated research project
of the IAEA the evaluation of cross sections of production routes of several medical radioisotopes, including
the so called generator isotopes, is in progress (Nichols,
2013). The production routes for a 178 W/178 Ta generator were previously compiled (not evaluated) in another
IAEA project dealing with the physical characteristics
and production methods of cyclotron produced radionuclides (Haji-Saeid et al., 2009). The compilation of the
available experimental cross section results showed no
∗ Corresponding
satisfactory data set. No cross section data are available for the nat Hf(α,xn)178 W reaction. Among the possible production routes we also measured cross sections
(up to 70 MeV) and made theoretical calculation for the
nat
Ta(p,x)178 W reaction (Uddin et al., 2004). We also investigated activation cross sections for deuteron induced
reactions on Ta up to 40 MeV, but cross section data for
178
W production were not reported (Hermanne et al.,
2009). In this work we experimentally investigate the
excitation function of the nat Hf(α,xn)178 W reaction and
the accompanying side reactions, and by re-evaluating
the spectra obtained in our earlier nat Ta(d,x) experiment we report cross sections of the nat Ta(d,x)178 W reaction. To show the capability of different nuclear reaction codes, the measured excitation functions are compared with the results obtained with ALICE-IPPE, EMPIRE and TALYS 1.4 (data from the TENDL-2013 online library) nuclear reaction codes. The thick target
yields were deduced and also compared with yields of
other charged particle production routes for 178 W. The
Ta is nearly monoisotopic, consists of 99.988% 181 Ta
and only 0.012 % 180 Ta, therefore under the present un-
author: ditroi@atomki.hu
Preprint submitted to Applied Radiation and Isotopes
December 2, 2014
arXiv:1412.0274v1 [nucl-ex] 30 Nov 2014
Measurements of ep → e0 π + n at 1.6 < W < 2.0 GeV and extraction of nucleon
resonance electrocouplings at CLAS
K. Park,35, 28 I.G. Aznauryan,35, 41 V.D. Burkert,35 K.P. Adhikari,28 M.J. Amaryan,28 S. Anefalos Pereira,16
H. Avakian,35 M. Battaglieri,17 R. Badui,10 I. Bedlinskiy,21 A.S. Biselli,9, 29 J. Bono,10 W.J. Briscoe,13
W.K. Brooks,36, 35 D.S. Carman,35 A. Celentano,17 S. Chandavar,27 G. Charles,20 L. Colaneri,18 P.L. Cole,14, 35
M. Contalbrigo,15 O. Cortes,14 V. Crede,11 A. D’Angelo,18, 31 N. Dashyan,41 R. De Vita,17 E. De Sanctis,16
A. Deur,35 C. Djalali,33 D. Doughty,7, 35 R. Dupre,20 H. Egiyan,35 A. El Alaoui,36 L. Elouadrhiri,35 L. El Fassi,28, ∗
P. Eugenio,11 G. Fedotov,33, 32 S. Fegan,17 R. Fersch,40, † A. Filippi,19 J.A. Fleming,37 B. Garillon,20 M. Gar¸con,6
N. Gevorgyan,41 G.P. Gilfoyle,30 K.L. Giovanetti,22 F.X. Girod,35 H.S. Joo,20 J.T. Goetz,27 E. Golovatch,32
R.W. Gothe,33 K.A. Griffioen,40 B. Guegan,20 M. Guidal,20 L. Guo,10, 35 H. Hakobyan,36, 41 C. Hanretty,39, ‡
M. Hattawy,20 K. Hicks,27 M. Holtrop,25 S.M. Hughes,37 C.E. Hyde,28 Y. Ilieva,33 D.G. Ireland,38 B.S. Ishkhanov,32
E.L. Isupov,32 D. Jenkins,43 H. Jiang,33 H.S. Jo,20 K. Joo,8 S. Joosten,34 D. Keller,39 M. Khandaker,14, 26
A. Kim,23, § W. Kim,23 A. Klein,28 F.J. Klein,5 V. Kubarovsky,35, 29 S.E. Kuhn,28 S.V. Kuleshov,36, 21 P. Lenisa,15
K. Livingston,38 H.Y. Lu,33 I .J .D. MacGregor,38 N. Markov,8 D. Martinez,14 B. McKinnon,38 V. Mokeev,35, 32
R.A. Montgomery,16, ¶ H. Moutarde,6 C. Munoz Camacho,20 P. Nadel-Turonski,35 S. Niccolai,20, 13 G. Niculescu,22, 27
I. Niculescu,22 M. Osipenko,17 A.I. Ostrovidov,11 M. Paolone,34 E. Pasyuk,35 P. Peng,39 W. Phelps,10 J.J. Phillips,38
S. Pisano,16 O. Pogorelko,21 J.W. Price,2 S. Procureur,6 Y. Prok,28, 39 D. Protopopescu,38 A.J.R. Puckett,8
B.A. Raue,10, 35 M. Ripani,17 A. Rizzo,18 G. Rosner,38 P. Rossi,16, 35 P. Roy,11 F. Sabati´e,6 C. Salgado,26
D. Schott,13 R.A. Schumacher,4 E. Seder,8 Y.G. Sharabian,35 A. Simonyan,41 Iu. Skorodumina,33, 44 E.S. Smith,35
G.D. Smith,37 N. Sparveris,34 P. Stoler,29 I.I. Strakovsky,13 S. Strauch,33 V. Sytnik,36 M. Taiuti,12, ∗∗ W. Tang,27
C.E. Taylor,14 Ye Tian,33 A. Trivedi,33 M. Ungaro,35, 29 H. Voskanyan,41 E. Voutier,24 N.K. Walford,5 D.P. Watts,37
X. Wei,35 L.B. Weinstein,28 M.H. Wood,3, 33 N. Zachariou,33 L. Zana,37 J. Zhang,35 Z.W. Zhao,39 and I. Zonta18
(The CLAS Collaboration)
1
Arizona State University, Tempe, Arizona 85287-1504, USA
California State University, Dominguez Hills, Carson, California 90747, USA
3
Canisius College, Buffalo, New York, USA
4
Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
5
Catholic University of America, Washington, D.C. 20064, USA
6
CEA, Centre de Saclay, Irfu/Service de Physique Nucl´eaire, 91191 Gif-sur-Yvette, France
7
Christopher Newport University, Newport News, Virginia 23606, USA
8
University of Connecticut, Storrs, Connecticut 06269, USA
9
Fairfield University, Fairfield Connecticut 06824, USA
10
Florida International University, Miami, Florida 33199, USA
11
Florida State University, Tallahassee, Florida 32306, USA
12
Universit`
a di Genova, 16146 Genova, Italy
13
The George Washington University, Washington, DC 20052, USA
14
Idaho State University, Pocatello, Idaho 83209, USA
15
INFN, Sezione di Ferrara, 44100 Ferrara, Italy
16
INFN, Laboratori Nazionali di Frascati, 00044 Frascati, Italy
17
INFN, Sezione di Genova, 16146 Genova, Italy
18
INFN, Sezione di Roma Tor Vergata, 00133 Rome, Italy
19
INFN, sez. di Torino, 10125 Torino, Italy
20
Institut de Physique Nucl´eaire ORSAY, Orsay, France
21
Institute of Theoretical and Experimental Physics, Moscow, 117259, Russia
22
James Madison University, Harrisonburg, Virginia 22807, USA
23
Kyungpook National University, Daegu 702-701, Republic of Korea
24
LPSC, Universit´e Grenoble-Alpes, CNRS/IN2P3, Grenoble, France
25
University of New Hampshire, Durham, New Hampshire 03824-3568, USA
26
Norfolk State University, Norfolk, Virginia 23504, USA
27
Ohio University, Athens, Ohio 45701, USA
28
Old Dominion University, Norfolk, Virginia 23529, USA
29
Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA
30
University of Richmond, Richmond, Virginia 23173, USA
31
Universita’ di Roma Tor Vergata, 00133 Rome Italy
32
Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119234 Moscow, Russia
33
University of South Carolina, Columbia, South Carolina 29208, USA
34
Temple University, Philadelphia, PA 19122, USA
35
Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
2
2
36
Universidad T´ecnica Federico Santa Mar´ıa, Casilla 110-V Valpara´ıso, Chile
37
Edinburgh University, Edinburgh EH9 3JZ, United Kingdom
38
University of Glasgow, Glasgow G12 8QQ, United Kingdom
39
University of Virginia, Charlottesville, Virginia 22901, USA
40
College of William and Mary, Williamsburg, Virginia 23187-8795, USA
41
Yerevan Physics Institute, 375036 Yerevan, Armenia
42
Argonne National Laboratory, Argonne, Illinois 60439, USA
43
Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0435, USA
44
M.V.Lomonosov Moscow State University,Leninskie Gory, Moscow 119991, Russia
Differential cross sections of the exclusive process ep → e0 π + n were measured with good precision
in the range of the photon virtuality Q2 = 1.8 − 4.5 GeV2 , and the invariant mass range of the
+
π n final state W = 1.6 − 2.0 GeV using the CEBAF Large Acceptance Spectrometer. Data were
collected with nearly complete coverage in the azimuthal and polar angles of the nπ + center-of-mass
system. More than 37,000 cross section points were measured. The contributions of the isospin I = 21
−
+
+
resonances N (1675) 52 , N (1680) 52 and N (1710) 21 were extracted at different values of Q2 using
a single-channel, energy-dependent resonance amplitude analysis. Two different approaches, the
unitary isobar model and the fixed-t dispersion relations, were employed in the analysis. We observe
−
significant strength of the N (1675) 25 in the A1/2 amplitude, which is in strong disagreement with
+
quark models that predict both transverse amplitudes to be strongly suppressed. For the N (1680) 52
we observe a slow changeover from the dominance of the A3/2 amplitude at the real photon point
(Q2 = 0) to a Q2 where A1/2 begins to dominate. The scalar amplitude S1/2 drops rapidly with Q2
+
consistent with quark model prediction. For the N (1710) 12 resonance our analysis shows significant
strength for the A1/2 amplitude at Q2 < 2.5 GeV2 .
PACS numbers: 13.40.Gp, 13.60.Le, 14.20.Gk, 25.30.Rw
I.
INTRODUCTION
The study of the excited states of the nucleon is an important step in the development of a fundamental understanding of the strong interaction [1]. While the existing
data on the low-lying resonances are consistent with the
well-studied SU (6) ⊗ O(3) constituent quark model classification, many open questions remain. On a fundamental level there exists only a very limited understanding
of the relationship between Quantum Chromo-Dynamics
(QCD), the field theory of the strong interaction, and the
constituent quark model (CQM) or alternative hadron
models, however recent developments in Lattice QCD,
most notably the predictions of the spectrum of N ∗ and
∆∗ states, have shown [2] that the same symmetry of
SU (6) ⊗ O(3) is likely at work here as is underlying the
spectrum in the CQM.
Experimentally, we still do not have sufficiently complete data that can be used to uncover unambiguously
the structure of the nucleon and its excited states in the
∗ Current
address:Mississippi State University, 125 Hilbun Hall,
Miss State, Mississippi 39762, USA
† Current address:Christopher Newport University, Newport News,
Virginia 23606, USA
‡ Current address:Thomas Jefferson National Accelerator Facility,
Newport News, Virginia 23606, USA
§ Current address:University of Connecticut, Storrs, Connecticut
06269, USA
¶ Current address:University of Glasgow, Glasgow G12 8QQ,
United Kingdom
∗∗ Current address:INFN, Sezione di Genova, 16146 Genova, Italy
entire resonance mass range. While this remains an important long term goal, very significant advances have
been made during the past decade that have enabled the
precise determination of resonance electrocouplings for a
set of lower mass states and in a wide space-time range.
Precise data have become available in recent years [3–10]
to study the transition from the nucleon ground state
to the ∆(1232), in π 0 electroproduction on the proton
with wide angular coverage and in a wide range of fourmomentum transfer Q2 . This has allowed for the determination of the magnetic dipole transition form factor
and the electric and scalar quadrupole transition, covering a range of 0 ≤ Q2 ≤ 7 GeV2 (we set c = 1).
This information, combined with precise cross section
and polarization data for the processes ep → e0 π 0 p [3, 4,
11], ep → e0 π + n [12–14] and ep → e0 ηp [15–17] in the second nucleon resonance region near W = 1.35 − 1.6 GeV
allowed for precise measurements of electrocouplings of
+
the ”Roper” resonance N (1440) 12 [18], which in the
CQM is the first radial excitation of the nucleon. These
results solved a longstanding question regarding the nature of this state. Precise results have also been obtained
−
−
for the transition to the N (1535) 12 and the N (1520) 32
states. Following these breakthroughs, the process ep →
+ −
2
epπ π was measured in the lower Q and low mass
range [19], and a reaction model was developed [20] that
enabled extraction of the electrocoupling amplitudes for
+
−
the resonances N (1440) 12 and N (1520) 32 [21] from this
channel. The two-pion results were consistent with the
results from the single pion analysis, and thus validated
the analysis approach for this more complex reaction
channel. This is a highly non-trivial result as the non-
Status of some P-wave baryon resonances
and importance of inelastic channels
Volker D. Burkert,1 Hiroyuki Kamano,2 Eberhard Klempt,3 Deborah R¨onchen,4 Andrey
6
ˇ
V. Sarantsev,3 Toru Sato,5 Alfred Svarc,
Lothar Tiator,7 and Ron L. Workman8
1
arXiv:1412.0241v1 [nucl-ex] 30 Nov 2014
2
Jefferson Lab, 12000 Jefferson Avenue, Newport News, Virginia 23606, USA
Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan
3
Helmholtz-Institut f¨
ur Strahlen- und Kernphysik, Universit¨
at Bonn, Germany
Petersburg Nuclear Physics Institute, Gatchina, Russia
4
Helmholtz-Institut f¨
ur Strahlen- und Kernphysik (Theorie) and Bethe Center for
Theoretical Physics, Universit¨
at Bonn, Nußallee 14-16, 53115 Bonn, Germany
5
Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
6
Rudjer Boˇskovi´c Institute, Bijeniˇcka cesta 54, P.O. Box 180, 10002 Zagreb, Croatia
7
Institut f¨
ur Kernphysik, Universit¨
at Mainz, D-55099 Mainz, Germany
8
Data Analysis Center at the Institute for Nuclear Studies, Department
of Physics, The George Washington University, Washington, D.C. 20052
(Dated: December 2, 2014)
Abstract
We analyze the current status of three P-wave baryon states N (1710)1/2+ , N (1900)3/2+ , and
∆(1600)3/2+ as given in the Review of Particles Physics (RPP). Since the evidence for a particle’s
existence is linked to its RPP ”star” rating, we discuss its subjective present definition. We also
present the accumulating evidence supporting these states and give our new ”star” rating recommendations.
PACS numbers:
I.
INTRODUCTION
In recent years, the field of light-flavor baryon spectroscopy has seen a tremendous increase in experimental activity. High-precision cross section and polarization data are now available, from numerous single and
double-meson photoproduction experiments, and these
have become the broadest source of information on new
baryon states. The bi-annually released Review of Particle Physics (RPP) is the primary source of information relied upon by researchers in the field of baryon
physics. The RPP tabulates baryon resonance candidates
together with their properties and provides an assessment
of their reliability, both overall and separately from pion
and photon induced reactions. We have therefore focused
our discussion on the ratings provided by this source.
The RPP assigns a star-rating from one to four stars
for baryon resonance candidates. The one and two-star
states are rated from poor to fair, whereas the three
and four-star states have a rating from likely to certain.
These higher-rated states appear in the Baryon Summary
Tables without reference to any star rating. The more
detailed Particle Listings tabulate overall and reactionspecific star ratings for each resonance. The three P+
wave baryon states, N (1710)(1/2)+ , N (1900)3/2 , and
+
∆(1600)3/2 , are presently given an overall three-star
rating, which prompts the question: Have these states
been confirmed or are they merely ’likely’ to exist?
It should be mentioned that neither the definition of
a star rating nor the ratings themselves have remained
static since these states were identified. Many states
were downgraded, with some three-star rated states being
eliminated, between the 1982 [1] and 1984 [2] editions of
the RPP. This upheaval was prompted by disagreements
between newer measurements and the older existing data
and analyses [3]. In particular, the N (1710)(1/2)+ was
demoted from a 4-star to a 3-star status, while the
∆(1600)(3/2)+ dropped from a 3-star to a 2-star status.
As a result, the ∆(1600)(3/2)+ was dropped from the
Baryon Summary Table. Its status was later raised back
to three stars [4], having been seen in subsequent analyses [5, 6] of the Virginia Tech and Kent State groups, the
uncertainty in its properties preventing a 4-star rating.
Many topics related to the extraction of resonance
properties, from the newly accumulated high-precision
data, were subjects of discussions at the 2014 ECT*
Workshop ”Exciting Baryons: Design and Analysis of
Complete Experiments for Meson Photoproduction” [7].
The presence of many experts in the field enabled a
meeting where the status of prominent 3-star resonances
Momentum sharing in imbalanced Fermi systems
Authors: O. Hen40*, M. Sargsian10, L.B. Weinstein27, E. Piasetzky40, H. Hakobyan34,39, D. W.
Higinbotham33, M. Braverman40, W.K. Brooks34, S. Gilad41, K. P. Adhikari27, J. Arrington1, G.
Asryan39, H. Avakian33, J. Ball7, N. A. Baltzell1, M. Battaglieri17, A. Beck40,43, S. May-Tal
Beck40,43, I. Bedlinskiy20, W. Bertozzi41, A. Biselli42, V. D. Burkert33, T. Cao32, D. S. Carman33,
A. Celentano17, S. Chandavar26, L. Colaneri18, P. L. Cole14,6,33, V. Crede11, A. D’Angelo18,30, R.
De Vita17, A. Deur33, C. Djalali32, D. Doughty8,33, M. Dugger2, R. Dupre19, H. Egiyan33, A. El
Alaoui1, L. El Fassi27, L. Elouadrhiri33, G. Fedotov32,31, S. Fegan17, T. Forest14, B. Garillon19, M.
Garcon7, N. Gevorgyan39, Y. Ghandilyan39, G. P. Gilfoyle29, F. X. Girod33, J. T. Goetz26, R. W.
Gothe32, K. A. Griffioen38, M. Guidal19, L. Guo10,33, K. Hafidi1, C. Hanretty37, M. Hattawy19, K.
Hicks26, M. Holtrop24, C. E. Hyde27, Y. Ilieva32,13, D. G. Ireland36, B.I. Ishkanov31, E. L.
Isupov31, H. Jiang32, H. S. Jo19, K. Joo9, D. Keller37, M. Khandaker14,25, A. Kim22, W. Kim22, F.
J. Klein6, S. Koirala27, I. Korover40, S. E. Kuhn27, V. Kubarovsky33, P. Lenisa15, W. I. Levine5,
K. Livingston36, M. Lowry33, H. Y. Lu32, I. J. D. MacGregor36, N. Markov9, M. Mayer27, B.
McKinnon36, T. Mineeva9, V. Mokeev19,33, A. Movsisyan15, C. Munoz Camacho19, B.
Mustapha1, P. Nadel-Turonski33, S. Niccolai19, G. Niculescu21, I. Niculescu21, M. Osipenko17, L.
L. Pappalardo15, R. Paremuzyan39, K. Park33,22, E. Pasyuk33, W. Phelps10, S. Pisano16, O.
Pogorelko20, J. W. Price3, S. Procureur7, Y. Prok27,37, D. Protopopescu36, A. J. R. Puckett9, D.
Rimal10, M. Ripani17, B. G. Ritchie2, A. Rizzo18, G. Rosner36, P. Rossi33, P. Roy11, F. Sabati ́e7,
D. Schott13, R. A. Schumacher5, Y. G. Sharabian33, G. D. Smith35, R. Shneor40, D. Sokhan36, S.
S. Stepanyan22, S. Stepanyan33, P. Stoler28, S. Strauch32,13, V. Sytnik34, M. Taiuti12, S.
Tkachenko37, M. Ungaro33, A. V. Vlassov20, E. Voutier23, N. K. Walford6, X. Wei33, M. H.
Wood4,32, S. A. Wood33, N. Zachariou32, L. Zana35,24, Z. W. Zhao37, X. Zheng37, and I. Zonta18.
(Jefferson Lab CLAS Collaboration)
Affiliations:
1
Argonne National Laboratory, Argonne, Illinois 60439.
2
Arizona State University, Tempe, Arizona 85287-1504.
3
California State University, Dominguez Hills, Carson, CA 90747.
4
Canisius College, Buffalo, NY.
5
Carnegie Mellon University, Pittsburgh, Pennsylvania 15213.
6
Catholic University of America, Washington, D.C. 20064.
7
CEA, Centre de Saclay, Irfu/Service de Physique Nucl ́eaire, 91191 Gif-sur-Yvette, France.
8
Christopher Newport University, Newport News, Virginia 23606.
9
University of Connecticut, Storrs, Connecticut 06269.
10
Florida International University, Miami, Florida 33199.
11
Florida State University, Tallahassee, Florida 32306.
12
Universita` di Genova, 16146 Genova, Italy.
Abstract: The atomic nucleus is composed of two different kinds of fermions, protons and
neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force
the majority fermions (usually neutrons) to have a higher average momentum. Our high-energy
electron scattering measurements using 12C, 27Al, 56Fe and 208Pb targets show that, even in heavy
neutron-rich nuclei, short-range interactions between the fermions form correlated highmomentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability
than neutrons to have momentum greater than the Fermi momentum.
This finding has
implications ranging from nuclear few body systems to neutron stars and may also be observable
experimentally in two-spin state, ultra-cold atomic gas systems.
Main Text: Many-body systems composed of interacting fermions are common in nature,
ranging from high-temperature superconductors and Fermi liquids to atomic nuclei, quark matter
and neutron-stars. Particularly intriguing are systems that include a short-range interaction that is
strong between unlike fermions and weak between fermions of the same kind. Recent theoretical
advances show that even though the underlying interaction can be very different, these systems
share several universal features (1-4). In all these systems, this interaction creates short-range
correlated (SRC) pairs of unlike fermions with a large relative momentum (krel > kF) and a small
center of mass (CM) momentum (ktot < kF), where kF is the Fermi momentum of the system. This
pushes fermions from low momenta (k < kF where k is the fermion momentum) to high momenta
(k > kF), creating a “high momentum tail”.
SRC pairs in atomic nuclei have been studied using many different reactions, including pickup,
stripping and electron and proton scattering. The results of these studies highlighted the
importance of correlations in nuclei, which lead to a high momentum tail and decreased
occupancy of low-lying nuclear states (5-13).
Recent experimental studies of balanced (symmetric) interacting Fermi systems, with an equal
number of fermions of the two kinds, confirmed these predictions of a high momentum tail
populated almost exclusively by pairs of unlike fermions (8-11,14-16). These experiments were
done using very different Fermi systems: protons and neutrons in atomic nuclei and two-spin
state ultra-cold atomic gasses. These systems span more than 15 orders of magnitude in Fermi
energy from 106 to 10-9 eV and exhibit different short-range interactions (predominantly a strong
tensor interaction in the nuclear systems (8,9,17,18), and a tunable Feshbach resonance in the