1. science
2. physics

The Speedster-EXD - A New Event-Triggered Hybrid CMOS
X-ray Detector
Christopher V. Griffitha , Abraham D. Falconea , Zachary R. Prieskorna , David N. Burrowsa
a The
Pennsylvania State University, 525 Davey Lab, University Park, PA, USA;
arXiv:1411.4655v1 [astro-ph.IM] 17 Nov 2014
ABSTRACT
We present preliminary characterization of the Speedster-EXD, a new event driven hybrid CMOS detector (HCD)
developed in collaboration with Penn State University and Teledyne Imaging Systems. HCDs have advantages
over CCDs including lower susceptibility to radiation damage, lower power consumption, and faster read-out
time to avoid pile-up. They are deeply depleted and able to detect x-rays down to approximately 0.1 keV.
The Speedster-EXD has additional in-pixel features compared to previously published HCDs including: (1) an
in-pixel comparator that enables read out of only the pixels with signal from an x-ray event, (2) four different
gain modes to optimize either full well capacity or energy resolution, (3) in-pixel CDS subtraction to reduce
read noise, and (4) a low-noise, high-gain CTIA amplifier to eliminate interpixel capacitance crosstalk. When
using the comparator feature, the user can set a comparator threshold and only pixels above the threshold will
be read out. This feature can be run in two modes including single pixel readout in which only pixels above the
threshold are read out and 3x3 readout where a 3x3 region centered on the central pixel of the X-ray event is read
out. The comparator feature of the Speedster-EXD increases the detector array effective frame rate by orders
of magnitude. The new features of the Speedster-EXD hybrid CMOS x-ray detector are particularly relevant to
future high throughput x-ray missions requiring large-format silicon imagers.
Keywords: hybrid CMOS, interpixel capacitance crosstalk, speedster, sparse read out, x-ray, comparator
1. INTRODUCTION
Future x-ray missions, such as SMART-X,1 will have much larger collecting areas than current missions such
as Chandra and XMM-Newton. Future missions will focus on observing much fainter objects, such as new xray bursts at early times in the universe (z > 7) which will explore cosmic structure and the birth of stars. In
addition to the faint objects, future x-ray missions will observe bright objects such as blazars. With the increased
collecting area of future missions combined with the observation of bright objects such as blazars, current x-ray
CCDs do not have fast enough read out times to keep up with the amount of x-rays that will be collected.
Hybrid CMOS x-ray detectors offer the fast read out times needed for future high throughput x-ray space
missions. Their pixel architecture enables the speed to capture the source image before multiple photons saturate
a pixel. Hybrid CMOS detectors also require less power and are more radiation hard than CCDs, adding to
mission lifetimes. A more thorough overview of the advantages of hybrid CMOS x-ray detectors can be seen in
Falcone et al. 2014.2
In this paper, we present two Speedster-EXD hybrid CMOS detectors and their characterization. The
Speedster-EXD detector has new in-pixel circuitry that includes a CTIA amplifier to eliminate interpixel capacitance crosstalk, in-pixel CDS subtraction to reduce noise, four different gain modes, and an in-pixel comparator
that enables the read out of only pixels with signal from an x-ray event. The detector can be run in full frame
read out mode where all pixels are read out, and in sparse mode where only pixels which contain an x-ray event
are read out. We discuss the performance of each of these features and present the measured read noise, energy
resolution, interpixel capacitance, and gain variation.
Further author information: (Send correspondence to C.V.G.)
C.V.G.: E-mail: cvg5124@psu.edu
1
arXiv:1411.4924v1 [physics.ins-det] 18 Nov 2014
LC-DET-2014-010
ECFA Detector R&D Panel
Review Report
The FCAL Collaboration
June 2013
Abstract
Two special calorimeters are foreseen for the instrumentation of the very forward region of an ILC or
CLIC detector; a luminometer (LumiCal) designed to measure the rate of low angle Bhabha scattering
events with a precision better than 10−3 at the ILC and 10−2 at CLIC, and a low polar-angle calorimeter
(BeamCal). The latter will be hit by a large amount of beamstrahlung remnants. The intensity and
the spatial shape of these depositions will provide a fast luminosity estimate, as well as determination
of beam parameters. The sensors of this calorimeter must be radiation-hard. Both devices will improve
the e.m. hermeticity of the detector in the search for new particles. Finely segmented and very compact
electromagnetic calorimeters will match these requirements. Due to the high occupancy, fast front-end
electronics will be needed. Monte Carlo studies were performed to investigate the impact of beam-beam
interactions and physics background processes on the luminosity measurement, and of beamstrahlung on
the performance of BeamCal, as well as to optimise the design of both calorimeters. Dedicated sensors,
front-end and ADC ASICs have been designed for the ILC and prototypes are available. Prototypes of
sensor planes fully assembled with readout electronics have been studied in electron beams.
Preprint typeset in JINST style - HYPER VERSION
arXiv:1411.4830v1 [physics.ins-det] 18 Nov 2014
The calibration system for the photomultiplier array
of the SNO+ experiment
R. Alvesa , S. Andringab , S. Bradburyc , J. Carvalhoa , D. Chauhanbd , K. Clarkek∗, I.
Coulter f †, F. Descampsg , E. Falke , L. Gurrianab , C. Krausd , G. Lefeuvree‡, A. Maiobhi ,
J. Maneirabh§, M. Mottrame , S. Peeterse , J. Rose j , L. Seabrab , J. Sinclaire , P.
Skensvedk , J. Waterfielde , R. Whitee , J.R. Wilsonl
a Laboratório
de Instrumentação e Física Experimental de Partículas and Departamento de
Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal,
b Laboratório de Instrumentação e Física Experimental de Partículas, Av. Elias Garcia, 14, 1◦ ,
1000-149 Lisboa, Portugal,
c School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom,
d Dept. of Physics and Astronomy, Laurentian University, Sudbury, Ontario P3E 2C6, Canada,
e Dept. of Physics and Astronomy, University of Sussex, Falmer Campus, Brighton BN1 9QH,
United Kingdom,
f Dept. of Physics, Oxford University, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH,
United Kingdom.
g Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720,
USA,
h Dep.to de Física, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, Edifício
C8, 1749-016 Lisboa, Portugal,
i Centro de Física Nuclear da Universidade de Lisboa, Av. Prof. Gama Pinto, 2, 1649-003
Lisboa, Portugal,
j Dept. of Physics, University of Liverpool, Liverpool L69 7ZE, United Kingdom,
k Queen’s University, Physics Dept., Kingston, Ontario K7L 3N6, Canada,
l School of Physics and Astronomy, Queen Mary, University of London, 327 Mile End Road,
London, E1 4NS, United Kingdom.
E-mail: maneira@lip.pt
A BSTRACT: A light injection system using LEDs and optical fibres was designed for the calibration
and monitoring of the photomultiplier array of the SNO+ experiment at SNOLAB. Large volume,
non-segmented, low-background detectors for rare event physics, such as the multi-purpose SNO+
experiment, need a calibration system that allow an accurate and regular measurement of the performance parameters of their photomultiplier arrays, while minimising the risk of radioactivity
ingress. The design implemented for SNO+ uses a set of optical fibres to inject light pulses from
external LEDs into the detector. The design, fabrication and installation of this light injection
system, as well as the first commissioning tests, are described in this paper. Monte Carlo simulations were compared with the commissioning test results, confirming that the system meets the
performance requirements.
–1–
Extraction of Physics Signals Near Threshold with Germanium Detectors in Neutrino
and Dark Matter Experiments
A.K. Soma,1, 2 G. Kiran Kumar,1, ∗ F.K. Lin,1 M.K. Singh,1, 2 H. Jiang,3 S.K. Liu,4 L. Singh,1, 2
Y.C. Wu,3 L.T. Yang,3 W. Zhao,3 M. Agartioglu,1, 5 G. Asryan,1 Y.C. Chuang,1 M. Deniz,1, 5, 6
C.L. Hsu,1 Y.H. Hsu,1 T.R. Huang,1 H.B. Li,1 J. Li,3 F.T. Liao,1 H.Y. Liao,1 C.W. Lin,1 S.T. Lin,1, 4
J.L. Ma,3 V. Sharma,1, 2 Y.T. Shen,1 V. Singh,2 J. Su,3 V.S. Subrahmanyam,1, 2 C.H. Tseng,1
J.J. Wang,1 H.T. Wong,1, † Y. Xu,1, 7 S.W. Yang,1 C.X. Yu,1, 7 X.C. Yuan,8 Q. Yue,3 and M. Zeyrek6
(TEXONO Collaboration)
1
Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
Department of Physics, Banaras Hindu University, Varanasi 221005, India.
3
Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
4
Department of Physics, Sichuan University, Chengdu 610065, China.
5
˙
Department of Physics, Dokuz Eyl¨
ul University, Buca, Izmir
35160, Turkey.
6
Department of Physics, Middle East Technical University, Ankara 06531, Turkey.
7
Department of Physics, Nankai University, Tianjin 300071, China.
8
Department of Nuclear Physics, Institute of Atomic Energy, Beijing 102413, China.
(Dated: November 19, 2014)
arXiv:1411.4802v1 [physics.ins-det] 18 Nov 2014
2
Germanium ionization detectors with sensitivities as low as 100 eVee open new windows for the
studies of neutrino and dark matter physics. The physics motivations of sub-keV germanium detectors are summarized. The amplitude of physics signals is comparable to those due to fluctuations of
the pedestal electronic noise. Various experimental issues have to be attended before the promises
of this new detector technique can be fully exploited. These include quenching factors, energy
definition and calibration, signal triggering and selection together with their associated efficiencies
derivation. The efforts and results of an R&D program to address these challenges are presented.
PACS numbers: 29.40.-n, 14.60.Lm, 95.35.+d.
I.
INTRODUCTION
Sensitivities and dynamic ranges on several important
research programs in neutrino and dark matter physics
can be significantly enhanced when the lower reach of detection − the “physics threshold” − can be extended [1].
This motivates efforts to characterize detector behavior
and to devise optimal analysis methods in this domain
where the amplitude of physics signals is comparable to
those of electronic noise.
We report our research program and results on advanced germanium (Ge) ionization detectors in this article. Following a survey on the physics topics relevant
to low-background low-threshold techniques, the crucial
aspects of detector operation and optimizations near electronic “noise-edge” are discussed. These include studies
on energy calibration, trigger rates, signal event selection
and their efficiencies. In particular, software techniques
are devised to extract physics signals below the noiseedge.
Data taken with point-contact Ge detectors with subkeV sensitivities were used to establish the results. However, the techniques would also be applicable to other detector systems, and at other energy ranges. Unless oth-
∗ Present
Address: Physics Department, KL University, Guntur
522502, India.
† Corresponding Author: htwong@phys.sinica.edu.tw
erwise stated, electron-equivalent energy (eVee ) is used
throughout in this article to denote detector response.
II.
SCIENTIFIC MOTIVATIONS
The objective of our research program is to develop
detectors with modular mass of O(1 kg), physics threshold of O(100eVee ) and background level at threshold of
O(1 kg−1 keV−1 day−1 ) [1]. Germanium semiconductors
in ionization mode were selected as the detection technique. When the “benchmark” specifications are fulfilled,
several important topics discussed in subsequent sections
can be experimentally pursued.
A.
Neutrino Electromagnetic Properties
Investigations on anomalous neutrino properties and
interactions can probe new physics beyond the Standard
Model. An avenue is on the studies of possible neutrino
electromagnetic interactions [2].
Neutrino magnetic moments (µν ) is an intrinsic neutrino property that describes possible neutrino-photon
couplings via its spin [3, 4]. The helicity is flipped in
µν -induced interactions. Observations of µν at levels relevant to present or future generations of experiments will
strongly favor the neutrinos are Majorana particles [5].
Conventionally, experimental studies on µν make use of
DESY 14-214
Extracting Hidden-Photon Dark Matter From an LC-Circuit
Paola Arias1 , Ariel Arza1 , Babette D¨obrich2 , Jorge Gamboa1 and Fernando Mendez1
arXiv:1411.4986v1 [hep-ph] 18 Nov 2014
1
Departmento de F´ısica, Universidad de Santiago de Chile, Casilla 307, Santiago, Chile
2
Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany
(Dated: November 19, 2014)
We point out that a cold dark matter condensate made of gauge bosons from an extra hidden
U(1) sector - dubbed hidden- photons - can create a small, oscillating electric density current. Thus,
they could also be searched for in the recently proposed LC-circuit setup conceived for axion cold
dark matter search by Sikivie, Sullivan and Tanner. We estimate the sensitivity of this setup for
hidden-photon cold dark matter and we find it could cover a sizable, so far unexplored parameter
space.
I.
INTRODUCTION
Nowadays, direct dark matter searches are mainly taking two alternative and complementary routes: one of
them aims to detect high-mass candidates – so-called
Weakly Interacting Massive Particles (WIMPs) – exploiting scattering experiments [1], and the other one looks
for light mass candidates – so-called Weakly Interacting
Slim particles (WISPs) – using precision experiments and
strong magnetic fields [2].
Among WISPs, the axion is a prime candidate. It was
originally proposed as a mechanism to solve the strong
CP problem [3]. Soon after this proposal, it was realized
that axions can be non-thermally produced by a misalignment mechanism, making it a strong cold dark matter
(CDM) candidate in the range of masses ma . 10−4 eV
[4].
A common feature among WISPs is their weak coupling to the Standard Model, and the smallness of their
masses. This is often a heritage from the high-energy
scale at which their underlying symmetries break. Many
indirect astrophysical observations have placed strong
constraints on these particles [5], but there is still plenty
of parameter space in which they could hide. In particular, the parameter space where they can be CDM remains
still quite open.
The WISPs relevant to this study are hidden sector
U (1) gauge bosons [6], also known as paraphotons, or hidden photons. Remarkably, the same non-thermal mechanism of axion CDM production also works to produce
a condensate of cold hidden photons [7, 8], whose viable
parameter space spans a wide range and remains almost
unconstrained by observations.
Consequently, experimental efforts have increased in
lasts years, and several precision experiments have been
and will be set up, like ADMX [9], ALPS [10], CAST,
CROWS [11], IAXO [12] (just to name a few) and help
to cover some of the unexplored parameter space.
Novel proposals, specially thought to reach the hinted
cold dark matter parameter space have emerged, such as
a dish antenna experiment [13]. In this study we want to
revisit the proposal made by Sikivie, Sullivan and Tanner
[14], in which they explore the particular form taken by
the Maxwell equations if axion CDM is present.
This new setup has interesting features; the first is the
simplicity of the idea, namely an LC-circuit carrying an
electric current generated by CDM axions in an external
magnetic field. Secondly, the signal produced by axions
can be amplified by the circuit, making it detectable by
magnetic flux detection techniques.
The aim of this letter is to show that hidden-photon
CDM can also provide an oscillating electric current,
without the need of an external electromagnetic field,
which can act as a source for the proposed experiment
[14]. Therefore, this setup can also hunt for these particles. We note that LC circuits have been mentioned in
[15] as hidden photons receivers, however not adapted to
the context of Dark Matter detection.
The paper is organized as follows: in section II we
briefly review the operating mechanism of the LC circuit
designed to detect axions. In section III we show how an
oscillating current from hidden- photon CDM emerges
from the coupling of the latter with photons, and we
obtain the sensitivity of the experiment proposed in [14]
for hidden photons. Finally in section IV we conclude.
II.
ESSENTIALS OF THE AXION SEARCH
WITH AN LC-CIRCUIT
Let us recall the essentials of the proposal made in [14].
The idea exploits the fact that the coupling of axions and
photons
L = −g aFµν F˜ µν ,
(1)
gives rise to a modified electrodynamics
∇×B−
∂E
da
= −g B
+ Jext
∂t
dt
(2)
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH
CERN-PH-EP-2014-254
08 October 2014
arXiv:1411.4969v1 [nucl-ex] 18 Nov 2014
Charged jet cross sections and properties
√
in proton-proton collisions at s = 7 TeV
ALICE Collaboration∗
Abstract
The differential charged jet cross sections, jet fragmentation distributions,
√ and jet shapes are measured in minimum bias proton-proton collisions at centre-of-mass energy s = 7 TeV using the ALICE detector at the LHC. Jets are reconstructed from charged particle momenta in the mid-rapidity
region using the sequential recombination kT and anti-kT as well as the SISCone jet finding algorithms with several resolution parameters in the range R = 0.2 – 0.6. Differential jet production cross
sections measured with the three jet finders are in agreement in the transverse momentum (pT ) injet,ch
< 100 GeV/c. They are also consistent with prior measurements carried out at
terval 20 < pT
the LHC by the ATLAS collaboration. The jet charged particle multiplicity rises monotonically with
increasing jet pT , in qualitative agreement with prior observations at lower energies. The transverse
profiles of leading jets are investigated using radial momentum density distributions as well as distributions of the average radius containing 80% (hR80 i) of the reconstructed jet pT . The fragmentation
of leading jets with R = 0.4 using scaled pT spectra of the jet constituents is studied. The measurements are compared to model calculations from event generators (PYTHIA, PHOJET, HERWIG).
The measured radial density distributions and hR80 i distributions are well described by the PYTHIA
model (tune Perugia-2011). The fragmentation distributions are better described by HERWIG.
c 2014 CERN for the benefit of the ALICE Collaboration.
Reproduction of this article or parts of it is allowed as specified in the CC-BY-3.0 license.
∗ See
Appendix A for the list of collaboration members
arXiv:1411.4874v1 [physics.acc-ph] 18 Nov 2014
KEK Preprint 2014-35
November 2014
H
A Multi-MW Proton/Electron Linac
at KEK
R. BELUSEVIC
IPNS, High Energy Accelerator Research Organization (KEK)
1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
belusev@post.kek.jp
Contents
1 Introduction
3
2 The Proposed Proton/Electron Facility at KEK
2.1 Main Characteristics of an ILC-Type Linac . . . . . . . . . . . . . . . . . . . . . .
2.2 Proton Injector (PI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
5
8
3 Physics at the Proposed Facility
3.1 Neutrino Flavor Oscillations and Leptonic CP Violation
3.2 Physics with Polarized Electrons and Positrons . . . . .
3.3 Rare Kaon Decays . . . . . . . . . . . . . . . . . . . . .
3.4 A Novel g -2 Experiment with Ultra-Slow Muons . . . .
.
.
.
.
9
9
11
13
15
4 An XFEL Based on the Proposed Superconducting Linac
4.1 A Simplified Description of X-Ray Free-Electron Lasers . . . . . . . . . . . . . . .
4.2 The European XFEL as a Prototype of the Proposed X-Ray FEL . . . . . . . . . .
16
16
19
5 Summary and Acknowledgements
22
References
2
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
arXiv:1411.4791v1 [hep-ph] 18 Nov 2014
Neutrinoless Double-Beta Decay: a Probe of
Physics Beyond the Standard Model
S.M. Bilenky
Joint Institute for Nuclear Research, Dubna, R-141980, Russia,
and
TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada
C. Giunti
INFN, Sezione di Torino, Via P. Giuria 1, I–10125 Torino, Italy
18 November 2014
Abstract
In the Standard Model the total lepton number is conserved. Thus, neutrinoless
double-β decay, in which the total lepton number is violated by two units, is a probe
of physics beyond the Standard Model. After a brief summary of the present status
of our knowledge of neutrino masses and mixing and an introduction to the seesaw
mechanism for the generation of light Majorana neutrino masses, in this review we
discuss the theory and phenomenology of neutrinoless double-β decay. We present the
basic elements of the theory of neutrinoless double-β decay, our view of the present
status of the challenging problem of the calculation of the nuclear matrix element of
the process and a summary of the experimental results.
1
Submitted to ”Chinese Physics C” Previous R&D of vibrating wire alignment technique for HEPS
WU Lei(吴蕾)1,2 WANG Xiao-long(王小龙)1,3 LI Chun-hua(李春华)1
1
Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
2
3
Abstract:
QU Hua-min(屈化民)1,3
University of Chinese Academy of Sciences, Beijing 100049, China
Dongguan Institute of Neutron Science (DINS), Dongguan 523808, China
The alignment tolerance of multipoles on a girder is better than 30m in the storage ring of High Energy Photon Source (HEPS)
which will be the next project at IHEP (Institute of High Energy Physics). This is difficult to meet the precision only using the traditional optical
survey method. In order to achieve this goal, vibrating wire alignment technique with high precision and sensitivity is considered to be used in
this project. This paper presents some previous research works about theory, scheme design and achievements.
vibrating wire, alignment, magnetic field measurement, accelerator, magnet
Key words:
PACS: 29.20.db
1
Vibrating wire technique has been used in some
Introduction
different projects in many labs. It has demonstrated the
HEPS will be a 5 GeV, 1296 meters circumference
potential to measure the magnetic center to the required
third generation synchrotron radiation facility with ultra
accuracy. These applications of vibrating wire are based
emittance and extremely high brightness. The emittance
on the same fundamental principle, but the specific
will be better than 0.1nmrad. The storage ring is a 48 cell
purposes are distinct. Vibrating wire is firstly be used at
7BA lattice. Figure 1 is one of 48 typical cells. The
Cornell University to find the magnetic center of
multipole girder that supports several quadrupoles and
superconducting quadrupoles placed inside the cryostat
sextuples is designed 3.8 meters. But this is not the final
for CESR [2]. Later, it has been used to find the solenoid
value, the lattice is still in the design [1].
magnetic center [3] and study the characterization of
undulator magnets [4]. In SLAC, this technique is used to
fiducialize the quadrupoles between undulator segments
for LCLS [5] and align quadrupole for FFTB. In CERN,
Fig. 1. One of 48 typical cells.
Table 1.
HEPS alignment tolerance.
its application is solenoid magnetic center finding [6]. In
PSI, vibrating wire is used to find the magnetic axis of
quadrupoles for Swiss Free Electron Laser [7]. In BNL,
Tolerances
Horizontal
Magnet to
Girder to
Magnet
Girder
0.03mm
0.05mm
this technique is used to align the quadrupoles and
sextupoles on one girder for NSLS-II [8].
Vibrating wire is based on measurement of the
magnetic axis to align the magnets. It is a further
vertical
0.03mm
0.05mm
Beam direction
0.5mm
0.5mm
diagrammatic sketch is like Figure 2 [9]. The specific
Roll angle
0.2mrad
0.2mrad
principle of this method is like that: a single conducting
evolution
of
pulsed
wire
method.
The
simple
wire is stretched through the magnet aperture and driven
Table 1 shows the alignment tolerance in HEPS. It is
by an alternating current. Transversal vibrations are
difficult to achieve the required accuracy using the
continuously excited by period Lorentz Force. By
traditional optical survey. So vibrating wire alignment
matching current frequency to one of the resonant modes
technique is considered to meet the tolerance 0.03mm
of wire, the vibration amplitude and sensitivity are
between magnet to magnet on one multipole girder.
enhanced and the magnetic induction intensity at the wire
Besides, automatic adjustment girder can help to achieve
position can be calculated. Move the wire across the
the tolerance 0.05mm between girder to girder.
aperture in horizontal direction(x) or vertical(y) direction,
The neutron anomaly in the γN → ηN cross section through the
looking glass of the flavour SU(3) symmetry
T. Boiko1 , V. Kuznetsov2 and M.V. Polyakov2,3∗
arXiv:1411.4375v1 [nucl-th] 17 Nov 2014
1
Bodwell High School, 955 Harbourside Drive, Vancouver, BC, Canada V7P 3S4
Petersburg Nuclear Physics Institute, Gatchina, 188300, St. Petersburg, Russia
3
Institute f¨
ur Theoretische Physik II, Ruhr-Universit¨at Bochum, D - 44780 Bochum,
Germany
2
Abstract
We study the implications of the flavour SU(3) symmetry for various interpretations
of the neutron anomaly in the γN → ηN cross section. We show that the explanation of the neutron anomaly due to interference of known N(1535) and N(1650)
resonances implies that N(1650) resonance should have a huge coupling to φ-meson
– at least 5 times larger than the corresponding ρ0 coupling. In terms of quark
degrees of freedom this means that the well-known N(1650) resonance must be a
“cryptoexotic pentaquark”– its wave function should contain predominantly an s¯
s
component.
It turns out that the “conventional” interpretation of the neutron anomaly by the interference of known resonances metamorphoses into unconventional physics picture
of N(1650).
Introduction
The discovery of the neutron anomaly† in the γN → ηN cross section was reported in
Ref. [1], in this paper the GRAAL data on the photon scattering off the deuteron were
analysed. Presently three other collaborations ( LNS [2],CBELSA/TAPS[3], and A2 [4])
confirmed the neutron anomaly beyond any doubts. For an illustration of the neutron
anomaly in γN → ηN we show on Fig. 1 the most recent results of the A2 collaboration
[4]. Furthermore the neutron anomaly at the same invariant mass of W ∼ 1680 MeV was
also observed in the Compton scattering [5].
In our view the observation of the neutron anomaly is the most striking discovery in
the field of the nucleon resonances spectroscopy during the last decade. It is important to
figure out the physics nature of the phenomenon. In the present paper we study the implications of the flavour SU(3) symmetry for various explanations of the neutron anomaly.
∗
e-mail address: maxim.polyakov@tp2.rub.de
Existence of the narrow (Γ ∼10-40 MeV) peak in the γn → ηn cross section around 1680 MeV and
its absence in the γp → ηp process
†
1
SNSN-323-63
November 15, 2014
arXiv:1411.4964v1 [hep-ex] 18 Nov 2014
Bs0 → µ+µ− at LHC
Flavio Archilli1
European Organisation for Nuclear Research
CH1211, Gen`eve 23, Switzerland
0
Rare leptonic decays of B(s)
mesons are sensitive probes of New Physics
effects. A combination combination of the CMS and LHCb analyses on
the search for the rare decays Bs0 → µ+ µ− and B 0 → µ+ µ− is pre+ −
0
+ −
sented. The branching fractions of Bs0 →
µ µ−9 and B 0→ µ +µ − are
measured
to be B(Bs0 → µ+ µ− ) = 2.8 +0.7
and B(B → µ µ ) =
−0.6 × 10
−10
3.9 +1.6
, respectively. A statistical significances of 6.2 σ is evalu−1.4 × 10
ated for Bs0 → µ+ µ− from the Wilks’ theorem while a significance of 3.0 σ
is measured for B 0 → µ+ µ− from the Feldman-Cousins procedure.
PRESENTED AT
Presented at the 8th International Workshop on the CKM
Unitarity Triangle (CKM 2014), Vienna, Austria, September
8-12, 2014
1
1
On behalf of LHCb and CMS collaborations.
Introduction
0
Limits on the rare B(s)
→ µ+ µ− decays Branching Fractions (BF) are one of the most
promising ways to constrain New Physics (NP) models. These decays are highly
suppressed in the Standard Model (SM), because they are flavour changing neutral current processes, that occur through Z penguin diagrams or W -box diagrams.
Moreover, the helicity suppression of axial vector terms makes these decays particularly sensitive to NP scalar and pseudoscalar contributions, such as extra Higgs
doublets, that can raise their BF with respect to SM expectations. The untagged
time-integrated SM predictions for these decays are [1]:
B(Bs0 → µ+ µ− )SM = (3.66 ± 0.23) × 10−9 ,
B(B 0 → µ+ µ− )SM = (1.06 ± 0.09) × 10−10 ,
which use the latest combined value for the top mass from LHC and Tevatron experiments [2]. Moreover, the ratio R of the BFs of these two modes proves to be
powerful to discriminate among models beyond the SM (BSM). This ratio is precisely
predicted in the SM to be:
B(B 0 → µ+ µ− )
τB 0
R=
=
B(Bs0 → µ+ µ− )
1/ΓsH
fB 0
fBs0
2 2
Vtd Vts s
4m2µ
1− 2
M 0
B
v
u
4m2µ
u
MB 0 t1− 2
M 0
s
MB 0
= 0.0295+0.0028
−0.0025
(1)
Bs
where τB 0 and 1/ΓsH are the lifetimes of the B 0 and of the heavy mass eigenstate of
0
0
0
the Bs0 ; MB(s)
is the mass and fB(s)
is the decay constant of the B(s)
meson; Vtd and
Vts are the elements of the CKM matrix and mµ is the mass of the muon. In BSM
models with minimal flavour violation property this quantity is predicted to be equal
to the SM ratio.
The LHCb collaboration has reported the first evidence of the Bs0 → µ+ µ− decay
with a 3.5 σ significance [3] in 2012 using 2 fb−1 collected during the first two years
of data taking. In 2013, CMS and LHCb presented their updated results based on
25 fb−1 and 3 fb−1 , respectively [4] [5]. The two measurements are in good agreement
with each other, and have comparable precisions; however, none of them is precise
enough to claim the first observation of the Bs0 → µ+ µ− decay.
A na¨ıve combination of LHCb and CMS results was presented during the European
Physical Society Conference on High Energy Physics in 2013 [6]. The result was:
B(Bs0 → µ+ µ− )SM = (2.9 ± 0.7) × 10−9 ,
−10
B(B 0 → µ+ µ− )SM = (3.6+1.6
.
−1.4 ) × 10
0
Despite they represent the most precise measurements on the rare decays B(s)
→
µ+ µ− , no accurate attempt was made to take into account for all the correlations
1
Eur. Phys. J. C manuscript No.
(will be inserted by the editor)
arXiv:1411.4963v1 [hep-ex] 18 Nov 2014
Measurement of√the forward charged particle pseudorapidity density in
pp collisions at s = 8 TeV using a displaced interaction point
The TOTEM Collaboration: G. Antchev20, P. Aspell13 , I. Atanassov13,22 , V. Avati13,
J. Baechler13 , V. Berardi8,7 , M. Berretti12,13 , E. Bossini12,23 , U. Bottigli12,23 , M. Bozzo10,9 ,
4,5 , A. Buzzo9 , F. S. Cafagna7 , M. G. Catanesi7 , C. Covault14 , M. Csan´
E. Brucken
¨
ad6,26 ,
6
13
2
14
17
9
T. Cs¨org˝o , M. Deile , M. Doubek , K. Eggert , V. Eremin , F. Ferro , A.
Fiergolski7,24 , F. Garcia4, V. Georgiev16, S. Giani13 , L. Grzanka15,25 , J. Hammerbauer16,
J. Heino4 , T. Hilden4,5 , A. Karev13, J. Kaˇspar1,13 , J. Kopal1,13 , V. Kundr´at1 ,
S. Lami11 , G. Latino12,23 , R. Lauhakangas4 , T. Leszko21 , E. Lippmaa3 , J. Lippmaa3 ,
M. V. Lokaj´ıcˇ ek1 , L. Losurdo12,23 , M. Lo Vetere10,9 , F. Lucas Rodr´ıguez13, M. Macr´ı9 ,
T. M¨aki4 , A. Mercadante7, N. Minafra8,13 , S. Minutoli9 , F. Nemes6,26 , H. Niewiadomski13 ,
4,5
¨
E. Oliveri12 , F. Oljemark4,5 , R. Orava4,5 , M. Oriunno18 , K. Osterberg
, P. Palazzi12,
16
1
7,8
13
Z. Peroutka , J. Proch´azka , M. Quinto , E. Radermacher , E. Radicioni7 ,
F. Ravotti13, E. Robutti9 , L. Ropelewski13 , G. Ruggiero13, H. Saarikko4,5 ,
A. Scribano12,23 , J. Smajek13 , W. Snoeys13 , J. Sziklai6 , C. Taylor14 , N. Turini12,23 ,
V. Vacek2 , J. Welti4,5 , J. Whitmore19, P. Wyszkowski15 , K. Zielinski15
1 Institute
of Physics of ASCR, Praha, Czech Republic,
Technical University, Praha, Czech Republic,
3 National Institute of Chemical Physics and Biophysics NICPB, Tallinn, Estonia,
4 Helsinki Institute of Physics, Helsinki, Finland,
5 Department of Physics, University of Helsinki, Helsinki, Finland,
6 MTA Wigner Research Center, RMKI Budapest, Hungary,
7 INFN Sezione di Bari, Bari, Italy,
8 Dipartimento Interateneo di Fisica di Bari, Italy,
9 INFN Sezione di Genova, Genova, Italy,
10 Universit`
a degli Studi di Genova, Genova, Italy,
11 INFN Sezione di Pisa, Pisa, Italy,
12 Universit`
a degli Studi di Siena and Gruppo Collegato INFN di Siena, Siena, Italy,
13 CERN, Geneva, Switzerland,
14 Case Western Reserve University, Dept. of Physics, Cleveland, OH, USA,
15 AGH University of Science and Technology, Krakow, Poland,
16 University of West Bohemia, Pilsen, Czech Republic,
17 Ioffe Physical - Technical Institute of Russian Academy of Sciences, St.Petersburg, Russia,
18 SLAC National Accelerator Laboratory, Stanford CA, USA,
19 Penn State University, Dept. of Physics, University Park, PA USA,
20 INRNE-BAS, Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia, Bulgaria,
21 Warsaw University of Technology, Warsaw, Poland.
22 Also at INRNE-BAS, Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia, Bulgaria,
23 Also at INFN Sezione di Pisa, Pisa, Italy,
24 Also at Warsaw University of Technology, Warsaw, Poland,
25 Also at Institute of Nuclear Physics, Polish Academy of Science, Cracow, Poland,
26 Also at Department of Atomic Physics, E¨
otv¨os University, Budapest, Hungary,
27 Also at Penn State University, Dept. of Physics, University Park, PA USA.
November 19, 2014
2 Czech
Abstract The pseudorapidity density of charged particles
dNch /dη is measured by the TOTEM experiment in pp col√
lisions at s = 8 TeV within the range 3.9 < η < 4.7 and
−6.95 < η < −6.9. Data were collected in a low intensity
LHC run with collisions occurring at a distance of 11.25 m
a Corresponding
author’s e-mail: mirko.berretti@cern.ch
from the nominal interaction point. The data sample is expected to include 96-97% of the inelastic proton-proton interactions. The measurement reported here considers charged
particles with pT > 0 MeV/c, produced in inelastic interactions with at least one charged particle in −7 < η < −6
or 3.7 < η < 4.8. The dNch /dη has been found to decrease
SNSN-323-63
November 19, 2014
arXiv:1411.4865v1 [hep-ex] 18 Nov 2014
Measurement of CP observables in Bs0 → Ds∓K ± at LHCb
Vladimir Gligorov
On behalf of the LHCb collaboration
CERN
Geneva, Switzerland
The time-dependent CP -violating observables accessible through Bs0 →
Ds∓ K ± decays have been measured for the first time using data corresponding to an integrated luminosity of 1 f b−1 collected in 2011 by the
LHCb detector. The CP -violating observables are found to be: Cf =
= 0.20 ± 0.41 ± 0.20,
0.53 ± 0.25 ± 0.04, A∆Γ
= 0.37 ± 0.42 ± 0.20, A∆Γ
f
f
Sf = 1.09±0.33±0.08, Sf = 0.36±0.34±0.08, where the first uncertainty
is statistical and the second systematic. Using these observables, the CKM
◦
◦
angle γ is determined to be (115+28
−43 ) modulo 180 at 68% CL, where the
uncertainty contains both statistical and systematic components.
PRESENTED AT
The 8th International Workshop on the CKM Unitarity
Triangle (CKM 2014)
Vienna, Austria, September 8-12, 2014
1
Introduction
Matter-antimatter asymmetry (CP violation) in weak interactions is described by a
single, irreducible phase in the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing
matrix [1, 2]. As this is a 3 × 3 unitary, hermitian, matrix, it can be represented as a
“Unitarity Triangle” in the complex plane. Since the matter-antimatter asymmetry
in the Standard Model is too small [3] to account for the disappearance of antimatter
following the Big Bang, it is reasonable to suppose that the Standard Model picture of
CP violation is not self-consistent and breaks down at some level. By experimentally
overconstraining the Unitarity Triangle, we are therefore directly probing the energy
scale of potential physics beyond the Standard Model.
0
The time-dependent decay rates of the |Bs0 (t = 0)i and |B s (t = 0)i flavour eigenstates to final state f are:
dΓB0 →f (t)
s
dt
(t)
0
B s →f
dΓ
dt
∆Γs t
∝ e−Γs t [cosh( ∆Γ2 s t ) + A∆Γ
f sinh( 2 ) + Cf cos(∆ms t) − Sf sin(∆ms t)],
∆Γs t
∝ e−Γs t [cosh( ∆Γ2 s t ) + A∆Γ
f sinh( 2 ) − Cf cos(∆ms t) + Sf sin(∆ms t)].
Similar decay rates hold for the conjugate processes. In the case where f ≡
Ds− K + , the four decay rates give five independently measureable CP -violating ob0
servables (“CP observables” henceforth), which are related to rDs K ≡ |A(Bs →
Ds− K + )/A(Bs0 → Ds− K + )|, the ratio of the magnitudes of the interfering diagrams,
as well as the strong phase difference δ and the weak phase difference γ − 2βs :
Cf =
2
1−rDsK
,
2
1+rDsK
A∆Γ
=
f
Sf =
−2rDsK cos(δ−(γ−2βs ))
,
2
1+rDsK
2rDsK sin(δ−(γ−2βs ))
,
2
1+rDsK
Sf =
A∆Γ
=
f
−2rDsK cos(δ+(γ−2βs ))
,
2
1+rDsK
−2rDsK sin(δ+(γ−2βs ))
,
2
1+rDsK
where βs ≡ arg(−Vts Vtb∗ /Vcs Vcb∗ ). These observables can therefore be used to measure γ, an angle of the Unitarity Triangle, with negligible [4] theoretical uncertainty.
2
Cancellation of ambiguities
As discussed in [5], the fact that ∆Γs is relatively large makes both the sinusoidal and
hyperbolic CP observables in Bs0 → Ds∓ K ± measurable and hence results in only a
twofold ambiguity on the measured value of the CKM angle γ and the strong phase
difference δ. In order to illustrate this point, it is useful to consider the constraints on
γ due to each of the observables listed in Eq. 1. These are illustrated in Fig. 1, which
clearly shows how the diagonal staggering of the sinusoidal and hyperbolic constraints
in the δ − γ plane cancels all but one of the ambiguous solutions.
1
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
arXiv:1411.4849v1 [hep-ex] 18 Nov 2014
CERN-PH-EP-2014-279
LHCb-PAPER-2014-061
November 18, 2014
Observation of two new Ξb− baryon
resonances
The LHCb collaboration†
Abstract
Two structures are observed close to the kinematic threshold in the Ξb0 π − mass
spectrum in a sample of proton-proton collision data, corresponding to an integrated
luminosity of 3.0 fb−1 , recorded by the LHCb experiment. In the quark model, two
baryonic resonances with quark content bds are expected in this mass region: the
+
+
spin-parity J P = 12 and J P = 32 states, denoted Ξb0− and Ξb∗− . Interpreting the
structures as these resonances, we measure the mass differences and the width of
the heavier state to be
m(Ξb0− ) − m(Ξb0 ) − m(π − ) = 3.653 ± 0.018 ± 0.006 MeV/c2 ,
m(Ξb∗− ) − m(Ξb0 ) − m(π − ) = 23.96 ± 0.12 ± 0.06 MeV/c2 ,
Γ(Ξb∗− ) = 1.65 ± 0.31 ± 0.10 MeV,
where the first and second uncertainties are statistical and systematic, respectively.
The width of the lighter state is consistent with zero, and we place an upper limit
of Γ(Ξb0− ) < 0.08 MeV at 95% confidence level. Relative production rates of these
states are also reported.
Submitted to Phys. Rev. Lett.
c CERN on behalf of the LHCb collaboration, license CC-BY-4.0.
†
Authors are listed at the end of this Letter.
SNSN-323-63
November 19, 2014
arXiv:1411.4822v1 [hep-ex] 18 Nov 2014
Direct CPV in two-body and multi-body charm decays at
LHCb
Evelina Gersabeck on behalf of the LHCb collaboration
Ruprecht-Karls-Universitaet Heidelberg
Physikalisches Institut
Im Neuenheimer Feld 226
69120 Heidelberg, Germany
The Standard Model predicts CP asymmetries in charm decays of
O(10−3) and the observation of significantly larger CP violation could
indicate non-Standard Model physics effects. During 2011 and 2012, the
LHCb experiment collected a sample corresponding to 3/f b yielding the
worlds largest sample of decays of charmed hadrons. This allowed the CP
violation in charm to be studied with unprecedented precision in many
two- body and multibody decay modes. The most recent LHCb searches
for direct CP violation are presented in these proceedings.
PRESENTED AT
Presented at the 8th International Workshop on the CKM
Unitarity Triangle (CKM 2014), Vienna, Austria,
September 8-12, 2014
1
Introduction
The excellent performance of the LHC and the LHCb
√ experiment, along with large
production cc cross sections for pp collisions at s of 7 and 8 TeV has enabled
unprecedentedly large samples of charm decays to be recorded during 2011 and 2012,
corresponding to 3/f b of integrated luminosity. These large samples allow the study
of CP violation (CPV) effects at a precision not achieved before in charm decays.
The data was taken with a regular swap of the polarity of the spectrometer dipole
magnet which can compensate for the left-right detector asymmetries to a first order.
Both charm decays, promptly produced in the primary pp interaction, and coming
from a parent beauty hadron are exploited at LHCb; this is indicated for each of the
presented analyses.
2
Time-integrated CP asymmetry in D 0 → h+h−
from semileptonic decays
A search for a time-integrated CP asymmetry in D 0 → h+ h− decays is performed
using the full dataset corresponding to 3/f b. The flavour of the initial D 0 state is
tagged by the charge of the muon in the semileptonic B → D 0 µ− νµ X decays.
The raw measured asymmetry for tagged D 0 messns to a final state f is given by:
Araw (f ) =
N(B → D 0 µ− X) − N(B → D 0 µ+ X)
,
N(B → D 0 µ− X) + N(B → D 0 µ+ X)
(1)
where N indicates the number of reconstructed events of a given decay after background subtraction, and X refers to the undetected final state particles from the
semileptonic B decay. The raw asymmetry is a sum of the physical CP asymmetry,
(ACP (f )), the production asymmetry (AP (B)) and detection asymmetry (AD (µ)) :
Araw (f ) = ACP (f ) + AP (B) + AD (µ).
(2)
As the quantity of interest is ACP (f ), the main experimental challenge is to separate
it from the nuisance asymmetries. An experimentally more robust variable, ∆ACP
can be constructed by taking the difference of the raw asymmetries measured in
D 0 → K + K − and D 0 → π + π − decays:
∆ACP = Araw (KK) − Araw (ππ),
(3)
and thus cancelling the production and the muon detection asymmetries to a first
order. Alternatively, for extracting ACP (KK), the detection and production asymmetries can be measured using Cabibbo-favoured (CF) B → D 0 (→ K − π + )µ− X decays
where no CPV is expected. An additional detection asymmetry, AD (Kπ), arises due
1
PNNL-SA-106625
November 19, 2014
arXiv:1411.4744v1 [hep-ex] 18 Nov 2014
New physics searches in B → D(∗)τ ν decays
Vikas Bansal
Pacific Northwest National Laboratory
902 Battelle Boulevard, 99352 - Richland, WA, USA,
for the Belle and BaBar Collaborations.
I review the current status of measurements involving semi-tauonic B
meson decay at the B-factories. I briefly discuss the experimental methods
and highlight the importance of background contributions especially from
poorly understood D∗∗ in this study. Perhaps this can also shed some light
on the discrepancy in the BaBar measurement of ratio of semi-tauonic and
semi-leptonic (e/µ) modes of B decay from the Standard Model (SM) at
3.2σ. I will also discuss one of the New Physics (NP) models that could be
experimentally sensitive in being distinguished from the Standard Model
(SM).
PRESENTED AT
8th International Workshop on the CKM Unitarity Triangle
(CKM 2014), Vienna, Austria, September 8-12, 2014.
1
Introduction
Search for New Physics (NP) via b → cτ ντ transitions is particularly interesting as
it involves third-generation fermions both in the initial and final states. Presence
of leptoquarks and charged Higgs boson in 2 Higgs doublet model (2HDM) could
enhance or suppress this decay rate [1]. In addition, study of τ polarizations in its
hadronic decay modes can also be sensitive to NP [2].
Reconstruction of B meson exclusive decay with τ lepton leads to two or three
undetected neutrinos depending on the τ decay mode. This requires additional constraints related to B meson production as are available at the B-factory experiments
- BaBar [3] and Belle [4]. B-factories produce Υ(4S) that almost exclusively decays
into BB system, thereby allowing full event reconstruction which is not possible at the
LHCb [5]. Hadronic tagging and inclusive tagging are two such popular reconstruction
techniques.
2
Experimental Results
Belle first observed B → D(∗) τ ν decays in 2007 using inclusive tagging method [6].
∗0
0
In 2010, Belle measured the decay rates B + → D τ + ντ and B + → D τ + ντ with the
same analysis technique and a larger data sample and additional D decay modes [7].
BaBar performed a hadronic tagging measurement of all four channels B 0 → D− τ + ντ
0
∗0
B 0 → D∗− τ + ντ , B + → D τ + ντ , and B + → D τ + ντ in 2008 which was superseded
by their 2012 result [8, 9] using full BaBar dataset. Belle also used hadronic tagging
technique to measure the four branching fractions [10]. All results along with the
standard model (SM) prediction [2] are summarized in Fig. 1, where purple, blue and
green lines denote Belle inclusive tagging, Belle hadronic tagging and BaBar hadronic
tagging results, respectively, and red lines with yellow bands show SM prediction.
Many experimental and theoretical uncertainties cancel out or are reduced when
one measures the ratios of the decay rates,
(∗)
R(D(∗) ) ≡
Γ(B → D τ + ντ )
(∗)
Γ(B → D `+ ν` )
.
(1)
∗
Figure 2 summarizes the measurements of the ratios R(D) and R(D ) along with
the SM prediction. Combination of the ratios gives an observed excess over the SM
by 3.2σ significance [9].
Figure 3 compares the measured values of R(D) and R(D∗ ) [8] in the context of
the type-II 2HDM to the theoretical predictions as a function of tan β/mH + . While
the measured values match the predictions tan β/mH + = 0.44 ± 0.02 GeV−1 from
R(D) and tan β/mH + = 0.75 ± 0.04 GeV−1 from R(D∗ ), the combination of the two
is excluded at 99.8% confidence level for any value of tan β/mH + .
1
arXiv:1411.4768v1 [hep-th] 18 Nov 2014
WU-HEP-14-10
EPHOU-14-019
Natural inflation with and without modulations
in type IIB string theory
Hiroyuki Abe1,∗, Tatsuo Kobayashi2†, and Hajime Otsuka1,‡
1
2
Department of Physics, Waseda University, Tokyo 169-8555, Japan
Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
Abstract
We propose a mechanism for the natural inflation with and without modulation in the framework of type IIB string theory on toroidal orientifold or orbifold. We explicitly construct
the stabilization potential of complex structure, dilaton and K¨
ahler moduli, where one of
the imaginary component of complex structure moduli becomes light which is identified as
the inflaton. The inflaton potential is generated by the gaugino-condensation term which
receives the one-loop threshold corrections determined by the field value of complex structure moduli and the axion decay constant of inflaton is enhanced by the inverse of one-loop
factor. We also find the threshold corrections can also induce the modulations to the original
scalar potential for the natural inflation. Depending on these modulations, we can predict
several sizes of tensor-to-scalar ratio as well as the other cosmological observables reported
by WMAP, Planck and/or BICEP2 collaborations.
∗
E-mail address: abe@waseda.jp
E-mail address: kobayashi@particle.sci.hokudai.ac.jp
‡
E-mail address: hajime.13.gologo@akane.waseda.jp
†
arXiv:1411.4651v1 [astro-ph.CO] 17 Nov 2014
Prepared for submission to JCAP
Tomographic-spectral approach for
dark matter detection in the
cross-correlation between cosmic shear
and diffuse gamma-ray emission
S. Camera,a M. Fornasa,b N. Fornengoc,d and M. Regisc,d
a CENTRA,
Instituto Superior T´ecnico, Universidade de Lisboa,
Avenida Rovisco Pais 1, 1049-001 Lisboa, Portugal
b School of Physics and Astronomy, University of Nottingham,
University Campus, Nottingham NG7 2RD, UK
c Dipartimento di Fisica, Universit`
a di Torino,
Via P. Giuria 1, 10125 Torino, Italy
d INFN, Sezione di Torino,
Via P. Giuria 1, 10125 Torino, Italy
E-mail: stefano.camera@tecnico.ulisboa.pt, fornasam@gmail.com,
fornengo@to.infn.it, regis@to.infn.it
Abstract. We recently proposed to cross-correlate the diffuse γ-ray emission with the gravitational lensing signal of cosmic shear. This represents a novel and promising strategy to search
for annihilating or decaying dark matter (DM) candidates. In the present work, we demonstrate the potential of a tomographic-spectral approach: measuring the cross-correlation in
separate bins of redshift and energy significantly improves the sensitivity to a DM signal.
Indeed, the power of the proposed technique stems from the capability of simultaneously
exploiting the different redshift scaling of astrophysical and DM components, their different
energy spectra and their different angular shapes. The sensitivity to a particle DM signal is
extremely promising even in the case the γ-ray emission induced by DM is a subdominant
component in the isotropic γ-ray background. We quantify the prospects of detecting DM
by cross-correlating the γ-ray emission from the Fermi large area telescope (LAT) with the
cosmic shear measured by the Dark Energy Survey, using data sets that will be available
in the near future. Under the hypothesis of a significant (but realistic) subhalo boost, such
a measurement can deliver a 5σ detection of DM, if the DM particle has a mass lighter
than 300 GeV and thermal annihilation rate. Data from the European Space Agency Euclid
satellite (launch planned for 2020) will be even more informative: if used to reconstruct the
properties of the DM particle, the cross-correlation of Euclid and Fermi-LAT will allow for
a measurement of the DM mass within a factor of 1.5–2, even for moderate subhalo boosts,
assuming the DM mass around 100 GeV and a thermal annihilation rate.
Keywords: dark matter theory, weak gravitational lensing, gamma-ray experiments.
Complex Saddle Points and Disorder Lines in QCD at finite
temperature and density
Hiromichi Nishimura
Faculty of Physics, University of Bielefeld, D-33615 Bielefeld, Germany
arXiv:1411.4959v1 [hep-ph] 18 Nov 2014
Michael C. Ogilvie and Kamal Pangeni
Department of Physics, Washington University, St. Louis, MO 63130 USA
(Dated: 11/17/14)
Abstract
The properties and consequences of complex saddle points are explored in phenomenological
models of QCD at non-zero temperature and density. Such saddle points are a consequence of the
sign problem, and should be considered in both theoretical calculations and lattice simulations. Although saddle points in finite-density QCD are typically in the complex plane, they are constrained
by a symmetry that simplifies analysis. We model the effective potential for Polyakov loops using
two different potential terms for confinement effects, and consider three different cases for quarks:
very heavy quarks, massless quarks without modeling of chiral symmetry breaking effects, and light
quarks with both deconfinement and chiral symmetry restoration effects included in a pair of PNJL
models. In all cases, we find that a single dominant complex saddle point is required for a consistent
description of the model. This saddle point is generally not far from the real axis; the most easily
noticed effect is a difference between the Polyakov loop expectation values hTrF P i and TrF P † ,
and that is confined to small region in the µ − T plane. In all but one case, a disorder line is found
in the region of critical and/or crossover behavior. The disorder line marks the boundary between
exponential decay and sinusoidally modulated exponential decay of correlation functions. Disorder
line effects are potentially observable in both simulation and experiment. Precision simulations
of QCD in the µ − T plane have the potential to clearly discriminate between different models of
confinement.
1
The effective QCD phase diagram and the critical end point
Alejandro Ayala1,3∗ , Adnan Bashir2 , J.J. Cobos-Mart´ınez2, Sa´
ul Hern´andez-Ortiz2, Alfredo Raya2
1
arXiv:1411.4953v1 [hep-ph] 18 Nov 2014
Instituto de Ciencias Nucleares, Universidad Nacional Aut´
onoma de M´exico,
Apartado Postal 70-543, M´exico Distrito Federal 04510, Mexico.
2
Instituto de F´ısica y Matem´
aticas, Universidad Michoacana de San Nicol´
as de Hidalgo,
Edificio C-3, Ciudad Universitaria, Morelia, Michoac´
an 58040, Mexico
3
Centre for Theoretical and Mathematical Physics, and Department of Physics,
University of Cape Town, Rondebosch 7700, South Africa.
We study the QCD phase diagram on the plane of temperature T and quark chemical potential
µ, modelling the strong interactions with the linear sigma model coupled to quarks. The phase
transition line is found from the effective potential at finite T and µ taking into accounts the plasma
screening effects. We find the location of the critical end point (CEP) to be (µCEP /Tc , T CEP /Tc ) ∼
(1.2, 0.8), where Tc is the (pseudo)critical temperature for the crossover phase transition at vanishing
µ. This location lies within the region found by lattice inspired calculations. The results show that
in the linear sigma model, the CEP’s location in the phase diagram is expectedly determined solely
through chiral symmetry breaking. The same is likely to be true for all other models which do
not exhibit confinement, provided the proper treatment of the plasma infrared properties for the
description of chiral symmetry restoration is implemented. Similarly, we also expect these corrections
to be substantially relevant in the QCD phase diagram.
PACS numbers: 25.75.Nq, 11.30.Rd, 11.15.Tk
Keywords: Chiral transition, linear sigma model, QCD phase diagram, critical end point.
The different phases in which matter, made up of
quarks and gluons, arranges itself depends, as for any
other substance, on the temperature and density, or
equivalently, on the temperature and chemical potentials.
Under the assumptions of beta decay equilibrium and
charge neutrality, the representation of the QCD phase
diagram is two dimensional. This is customary plotted
with the light-quark chemical potential µ as the horizontal variable and the temperature T as the vertical
one. µ is related to the baryon chemical potential µB by
µB = 3µ.
Most of our knowledge of the phase diagram is restricted to the µ = 0 axis. The phase diagram is, by and
large, unknown. For physical quark masses and µ = 0,
lattice calculations have shown [1] that the change from
the low temperature phase, where the degrees of freedom
are hadrons, to the high temperature phase described by
quarks and gluons, is an analytic crossover. The phase
transition has a dual nature: on the one hand the colorsinglet hadrons break up leading to deconfined quarks
and gluons; this is dubbed as the deconfinement phase
transition. On the other hand, the dynamically generated
component of quark masses within hadrons vanishes; this
is referred to as chiral symmetry restoration.
Lattice calculations have provided values for the
crossover (pseudo)critical temperature Tc for µ = 0
and 2+1 quark flavors using different types of improved
rooted staggered fermions [2]. The MILC collaboration [3] obtained Tc = 169(12)(4) MeV. The RBCBielefeld collaboration [4] reported Tc = 192(7)(4) MeV.
∗ Corresponding
author: ayala@nucleares.unam.mx
The Wuppertal-Budapest collaboration [5] has consistently obtained smaller values, the latest being Tc =
147(2)(3) MeV. The HotQCD collaboration [6] has computed Tc = 154(9) MeV. The differences could perhaps
be attributed to different lattice spacings.
The picture presented by lattice QCD for T ≥ 0, µ = 0
cannot be easily extended to the case µ 6= 0, the reason
being that standard Monte Carlo simulations can only
be applied to the case where either µ = 0 or is purely
imaginary. Simulations with µ 6= 0 are hindered by the
sign problem, see, for, example, [7], though some mathematical extensions of lattice techniques [8] can probe
this region. Schwinger-Dyson equation studies support
these findings and can successfully explore all region of
the phase space [9].
On the other hand a number of different model approaches indicate that the transition along the µ axis,
at T = 0, is strongly first order [10]. Since the first order line originating at T = 0 cannot end at the µ = 0
axis which corresponds to the starting point of the crossover line, it must terminate somewhere in the middle of
the phase diagram. This point is generally referred to as
the critical end point (CEP). The location and observation of the CEP continue to be at the center of efforts
to understand the properties of strongly interacting matter under extreme conditions. The mathematical extensions of lattice techniques place the CEP in the region
(µCEP /Tc , T CEP /Tc ) ∼ (1.0 − 1.4, 0.9).
In the first of Refs. [9], it is argued that the theoretical
location of the CEP depends on the size of the confining
length scale used to describe strongly interacting matter at finite density/temperature. This argument is supported by the observation that the models which do not
account for this scale [11–14] produce either a CEP closer
Compatible abelian symmetries in N-Higgs-Doublet Models
C. C. Nishi∗
Universidade Federal do ABC - UFABC, 09.210-170, Santo Andr´e, SP, Brazil and
Maryland Center for Fundamental Physics,
University of Maryland, College Park, MD 20742, USA
We analyze the compatibility between abelian symmetries acting in two different sectors
of a theory using the Smith Normal Form method. We focus on N-Higgs-doublet models
(NHDMs) and on the compatibility between symmetries in the Higgs potential and in the
arXiv:1411.4909v1 [hep-ph] 18 Nov 2014
Yukawa interactions, which were separately analyzed in previous works. It is shown that
two equal (isomorphic) symmetry groups that act in two separate sectors are not necessarily
compatible in the whole theory and an upper bound is found for the size of the group that
can be implemented in the entire NHDM. We also develop useful techniques to analyze
compatibility and extend a symmetry from one sector to another.
I.
INTRODUCTION
Symmetry has always played a crucial role in our understanding of fundamental physics. The
construction of the current framework – the Standard Model (SM) of particle physics – has culminated in 2012 with the discovery of the Higgs boson [1], the particle that results from the breaking
of the electroweak symmetry in its simplest form. Hence, it was also a successful attempt to probe
a hidden (broken) symmetry in nature and its breaking mechanism. However, as we probe higher
and higher energies, new symmetries may emerge as key ingredients to understand the physics
beyond the SM.
As we try to guess which new symmetry governs the physics above the electroweak scale, we are
also confronted with the question of what is the breaking scale and what could be the signatures
after breaking. One old but fruitful example where the symmetry should (usually) be broken at
very high energies is B −L symmetry, a symmetry that might be linked to the smallness of neutrino
masses (see, e.g., Ref. [2] and references therein).
In parallel to continuous symmetries, discrete symmetries are also possible ingredients with
which we can understand flavor (for a review, see e.g. Refs.[3]) and the stability of dark matter
(with, e.g., R-parity [4] or matter parity [5]). In the effort to classify and discover useful abelian
∗
Electronic address: celso.nishi@ufabc.edu.br
Strong–Field Quantum Electrodynamics and Muonic Hydrogen
U. D. Jentschura
arXiv:1411.4889v1 [hep-ph] 14 Nov 2014
Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409-0640, USA
We explore the possibility of a breakdown of perturbative quantum electrodynamics in light
muonic bound systems, notably, muonic hydrogen. The average electric field seen by a muon
orbiting a proton is shown to be comparable to hydrogenlike Uranium and, notably, larger than
the electric field achievable using even the most advanced strong-laser facilities. Following Maltman
and Isgur who have shown that fundamental forces such as the meson exchange force may undergo
a qualitative change in the strong-coupling regime, we investigate a concomitant possible existence
of muon-proton and electron-proton contact interactions, of nonperturbative origin, and their
influence on transition frequencies in light one-muon ions.
PACS numbers: 12.20.Ds, 11.25.Tq, 11.15.Bt
I.
INTRODUCTION
e−
The recent muonic hydrogen experiments [1, 2] have
given rise to the most severe discrepancy of the predictions of quantum electrodynamics with experiment
recorded over the last few decades. In short, both (electronic, atomic) hydrogen experiments (for an overview
see Ref. [3]) as well as recent scattering experiments lead
to a proton charge radius of about hrp i ≈ 0.88 fm, while
the muonic hydrogen experiments [1, 2] favor a proton
charge radius of about hrp i ≈ 0.84 fm. The observed difference is consistent with two muonic scattering experiments [4, 5] that were carried out about four decades ago
and roughly observe a 4 % lower cross section for muons
scattering off of protons as opposed to electrons being
scattered off the same target. (If one assumes that the
shape of the electric Sachs form factor is the same for
electron compared to muon scattering, the cross section
is proportional to the square of the charge radius.)
All attempts to find a conceivable explanation for the
discrepancy based on a calculational error in bound-state
quantum electrodynamics [6] or a “subversive” virtual
particle [7–9] have failed, mostly because of tight constraints on these terms set by other low-energy tests of
quantum electrodynamics [7]. Furthermore, attempts to
reconcile the difference based on higher moments of the
proton charge distribution (its “higher-order shape”, see
Ref. [8]) face difficulty when confronted with scattering
experiments which set relatively tight constraints on the
higher-order terms.
II.
NONPERTURBATIVE LEPTON PAIRS
Recently [10, 11], one of the few remaining theoretical
explanations for the discrepancy, namely, the existence
of a contact interaction of electron and proton, has been
investigated. A contact interaction [10, 11] of nonperturbative origin [10, 11] between the muon and proton,
nonuniversal for leptons, can be represented as a simple
contact interaction diagram (four-fermion vertex), pro-
µ−
e−
p
p
p
µ−
p
a
FIG. 1: The existence of a (conceivably nonuniversal) contact
interaction of nonperturbative origin, cannot be ruled out in
electron-proton [Fig. (a)] and muon-proton [Fig. (b)] scattering processes.
portional to δ 3 (r) in coordinate space (see Fig. 1). The
conjecture formulated in Refs. [10, 11] follows Maltman
and Isgur who argued [12] that the nuclear force that
binds the nucleons together, needs to be modified beyond
simple meson exchange for small nuclei with a considerable overlap of the wave functions of two, three, or four
hadrons.
One may ask if the Hamiltonian given in Eq. (11) of
Ref. [10],
Hann = ǫp
3παQED 3
δ (r) ,
2m2e
(1)
where the subscript “ann” denotes the virtual annihilation channel and ǫp is a parameter that measures the
amount of electron-positron pairs within the proton, has
any predictive power. According to Eq. (13) of Ref. [10],
a value of ǫp = 2.1 × 10−7 is sufficient to explain the
proton radius puzzle. The Hamiltonian (1) it predicts
a specific form of the frequency correction beyond perturbative quantum electrodynamics, namely, that of the
Dirac-δ potential, which mimics the effect of an apparent
change in the square of the proton radius (nuclear size
effect).
The parameter ǫp , however, cannot be universal and
should depend on the specific details of the proton (p)
wave function. A breakdown of perturbative quantum
Relating quarks and leptons with the T7 flavour group
Cesar Bonilla,1∗ Stefano Morisi,2† Eduardo Peinado,3‡ and J. W. F. Valle,1§
1
Instituto de F´ısica Corpuscular (CSIC-Universitat de Val`encia),
Apdo. 22085, E-46071 Valencia, Spain.
2
3
DESY, Platanenallee 6, D-15735 Zeuthen, Germany.
Instituto de F´ısica, Universidad Nacional Aut´
onoma de M´exico,
A.P. 20-364, M´exico 01000, D.F., M´exico.
arXiv:1411.4883v1 [hep-ph] 18 Nov 2014
(Dated: November 19, 2014)
In this letter we present a model for quarks and leptons based on T7 as flavour
symmetry, predicting a canonical mass relation between charged leptons and downtype quarks proposed earlier. Neutrino masses are generated through a Type-I seesaw
mechanism, with predicted correlations between the atmospheric mixing angle and
neutrino masses. Compatibility with oscillation results lead to lower bounds for the
lightest neutrino mass as well as for the neutrinoless double beta decay rates, even
for normal neutrino mass hierarchy.
PACS numbers: 11.30.Hv 14.60.-z 14.60.Pq 12.60.Fr 14.60.St 23.40.Bw
I.
INTRODUCTION
Ever since the discovery of the muon in the thirties particle physicists have wondered on
a possible simple understanding of fermion mass and mixing patterns. The experimental
confirmation of neutrino oscillations [1–4] has brought again the issue into the spotlight. Yet
despite many attempts, so far the origin of neutrino mass and its detailed flavour structure
remains one of the most well-kept secrets of nature. In particular the observed values of
neutrino oscillation parameters [5] pose the challenge to figure out why lepton mixing angles
are so different to those of quarks. Indeed the sharp differences between the flavour mixing
parameters characterizing the quark and lepton sectors escalate the complexity of the flavour
∗
†
‡
§
Electronic
Electronic
Electronic
Electronic
address:cesar.bonilla@ific.uv.es
address:stefano.morisi@gmail.com
address:epeinado@fisica.unam.mx
address:valle@ific.uv.es
November 19, 2014
LPT-Orsay-14-85
arXiv:1411.4878v1 [hep-ph] 18 Nov 2014
LAPTH-229/14
Photon-Jet cross sections in Deep-Inelastic Scattering
P. Aurenche1,a and M. Fontannaz2,b
1
LAPTh, Universit´e de Savoie, CNRS
BP 110, Chemin de Bellevue, 74941 Annecy-le-Vieux Cedex, France
2
Laboratoire de Physique Th´eorique, UMR 8627 du CNRS,
Universit´e Paris-Sud, Bˆ
atiment 210, 91405 Orsay Cedex, France
Abstract
We present the complete next-to-leading order calculation of isolated prompt photon production in association with a jet in deep-inelastic scattering. The calculation involves, direct, resolved
and fragmentation contributions. It is shown that defining the transverse momenta in the proton
virtual-photon frame (CM∗ ), as usually done, or in the laboratory frame (LAB), as done in some
experiments, is not equivalent and leads to important differences concerning the perturbative approach. In fact, using the latter frame may preclude, under certain conditions, the calculation of
the next-to-leading order correction to the important resolved component. A comparaison with the
latest ZEUS data is performed and good agreement is found in the perturbatively stable regions.
a
e-mail: patrick.aurenche@lapth.cnrs.fr
b
e-mail: michel.fontannaz@th.u-psud.fr
Prepared for submission to JHEP
arXiv:1411.4876v1 [hep-ph] 18 Nov 2014
Bayesian Model comparison of Higgs couplings
Johannes Bergstr¨
oma Stella Riadb
a
Departament d’Estructura i Constituents de la Mat`eria and Institut de Ciencies del Cosmos,
Universitat de Barcelona, Diagonal 647, E-08028 Barcelona, Spain
b
Department of Theoretical Physics, School of Engineering Sciences,
Royal Institute of Technology (KTH) – AlbaNova University Center,
Roslagstullsbacken 21, S-106 91 Stockholm, Sweden
E-mail: bergstrom@ecm.ub.edu, sriad@kth.se
Abstract: We investigate the possibility of contributions from physics beyond the Standard Model (SM) to the Higgs couplings, in the light of the LHC data. The work is
performed within an interim framework where the magnitude of the Higgs production and
decay rates are rescaled though Higgs coupling scale factors. We perform Bayesian parameter inference on these scale factors, concluding that there is good compatibility with the
SM. Furthermore, we carry out Bayesian model comparison on all models where any combination of scale factors can differ from their SM values and find that typically models with
fewer free couplings are strongly favoured. We consider the evidence that each coupling
individually equals the SM value, making the minimal assumptions on the other couplings.
Finally, we make a comparison of the SM against a single “not-SM” model, and find that
there is moderate to strong evidence for the SM.
Keywords: Statistical methods, Higgs physics
KIAS-P14068
LPT-Orsay-14-86
Effect of Degenerated Particles on
Internal Bremsstrahlung of Majorana Dark Matter
arXiv:1411.4858v1 [hep-ph] 18 Nov 2014
Hiroshi Okada1∗ and Takashi Toma2†
1
School of Physics, KIAS, Seoul 130-722, Korea
2
Laboratoire de Physique Th´eorique,
Universit´e de Paris-Sud 11, Bˆat. 210, 91405 Orsay Cedex, France
Abstract
Gamma-ray generated by annihilation or decay of dark matter can be its smoking
gun signature. In particular, gamma-ray coming from internal bremsstrahlung of
dark matter is promising since it can be a leading emission of sharp gamma-ray.
However if thermal production of Majorana dark matter is considered, the derived
cross section for internal bremsstrahlung becomes too small to be observed by future
gamma-ray experiments. We consider a framework to achieve an enhancement of
the cross section by taking into account degenerated particles with dark matter. We
find that the enhancement of about order one is possible without conflict with the
dark matter relic density. Due to the enhancement, it would be tested by the future
experiments such as GAMMA-400 and CTA.
∗
†
hokada@kias.re.kr
takashi.toma@th.u-psud.fr
DO-TH 14/25, QFET-2014-21
Diagnosing lepton-nonuniversality in b → s``
Gudrun Hiller
Institut f¨
ur Physik, Technische Universit¨
at Dortmund, D-44221 Dortmund, Germany
arXiv:1411.4773v1 [hep-ph] 18 Nov 2014
Martin Schmaltz
Physics Department, Boston University, Boston, MA 02215
Ratios of branching fractions of semileptonic B decays, (B → Hµµ) over (B →
Hee) with H = K, K ∗ , Xs , K0 (1430), φ, . . . are sensitive probes of lepton universality.
In the Standard Model, the underlying flavor changing neutral current process b →
s`` is lepton flavor universal. However models with new flavor violating physics
above the weak scale can give substantial non-universal contributions. The leading
contributions from such new physics can be parametrized by effective dimension six
operators involving left- or right-handed quarks. We show that in the double ratios
RXs /RK , RK ∗ /RK and Rφ /RK the dependence on new physics coupling to lefthanded quarks cancels out. Thus a measurement of any of these double ratios is
a clean probe of flavor nonuniversal physics coupling to right-handed quarks. We
also point out that the observables RXs , RK ∗ , RK0 (1430) and Rφ depend on the same
combination of Wilson coefficients and therefore satisfy simple consistency relations.
I.
INTRODUCTION
Ratios of branching fractions of rare semileptonic B decays into dimuons over dielectons
[1],
RH =
¯ → Hµµ)
¯
B(B
,
¯ → Hee)
¯
B(B
H = K, K ∗ , Xs , Kπ, . . .
(1)
are sensitive tests of lepton universality. The most significant theoretical and experimental
uncertainties, including hadronic ones, are lepton flavor universal and drop out in the ratio,
allowing for particularly clean tests of the standard model (SM).
arXiv:1411.4749v1 [hep-ph] 18 Nov 2014
Vacuum properties of open charmed mesons in a
chiral symmetric model
Walaa I. Eshraim
Institute for Theoretical Physics, Goethe-University, Max-von-Laue-Str. 1,
60438 Frankfurt am Main, Germany
E-mail: weshraim@th.physik.uni-frankfurt.de
Abstract. We present a U (4)R × U (4)L chirally symmetric model, which in addition to scalar
and pseudoscalar mesons also includes vector and axial-vector mesons. A part from the three
new parameters pertaining to the charm degree of freedom, the parameters of the model are fixed
from the Nf = 3 flavor sector. We compute open charmed meson masses, weak decay constants,
and the (OZI-dominant) strong decays of open charmed mesons. A precise description of decays
of open charmed states is important for the CBM and PANDA experiments at the future FAIR
facility.
1. Introduction
Open charmed mesons, composite states of charm quark (c) and up (u), down (d), or strange
(s) antiquark, were observed two years later than the discovery of the J/ψ particle in 1974.
Since that time, the study of charmed meson spectroscopy and decays has made significant
experimental [1, 2, 3] and theoretical process [4, 5, 6, 7]. We show in the present work that how
the original SU (3) flavor symmetry of hadrons can be extended to SU (4) in the framework of a
chirally symmetric model with charm as an extra quantum number. Note that, chiral symmetry
is strongly explicitly broken by the current charm quark mass.
The development of an effective hadronic Lagrangian plays an important role in the
description of the masses and the interactions of low-lying hadron resonances [8]. To this
end, we developed the so-called extended Linear Sigma Model (eLSM) in which (pseudo)scalar
and (axial-)vector qq mesons and additional scalar and pseudoscalar glueball fields are the
basic degrees of freedom. The eLSM has already shown success in describing the vacuum
phenomenology of the nonstrange-strange mesons [9, 10, 11, 12, 13]. The eLSM emulates
the global symmetries of the QCD Lagrangian; the global chiral symmetry (which is exact
in the chiral limit), the discrete C, P, and T symmetries, and the classical dilatation (scale)
symmetry. When working with colorless hadronic degrees of freedom, the local color symmetry
of QCD is automatically preserved. In eLSM the global chiral symmetry is explicitly broken
by non-vanishing quark masses and quantum effects [14], and spontaneously by a non-vanishing
expectation value of the quark condensate in the QCD vacuum [15]. The dilatation symmetry
is broken explicitly by the logarithmic term of the dilaton potential, by the mass terms, and by
the U (1)A anomaly.
In these proceedings, we present the outline of the extension of the eLSM from the threeflavor case to the four-flavor case including the charm quark [16, 17, 18]. Most parameters of our
CTPU-14-12
Peccei-Quinn invariant singlet extended SUSY
with anomalous U (1) gauge symmetry
Sang Hui Im∗ and Min-Seok Seo†
arXiv:1411.4724v1 [hep-ph] 18 Nov 2014
Center for Theoretical Physics of the Universe,
Institute for Basic Science (IBS), Daejeon 305-811, Korea
Abstract
Recent discovery of the SM-like Higgs boson with mh ≃ 125 GeV motivates an extension of
the minimal supersymmetric standard model (MSSM), which involves a singlet Higgs superfield
with a sizable Yukawa coupling to the doublet Higgs superfields. We examine such singlet-extended
SUSY models with a Peccei-Quinn (PQ) symmetry that originates from an anomalous U (1)A gauge
symmetry. We focus on the specific scheme that the PQ symmetry is spontaneously broken at an
√
intermediate scale vPQ ∼ mSUSY MPl by an interplay between Planck scale suppressed operators
√
and tachyonic soft scalar mass mSUSY ∼ DA induced dominantly by the U (1)A D-term DA . This
scheme also results in spontaneous SUSY breaking in the PQ sector, generating the gaugino masses
√
M1/2 ∼ DA when it is transmitted to the MSSM sector by the conventional gauge mediation
mechanism. As a result, the MSSM soft parameters in this scheme are induced mostly by the
U (1)A D-term and the gauge mediated SUSY breaking from the PQ sector, so that the sparticle
masses can be near the present experimental bounds without causing the SUSY flavor problem.
The scheme is severely constrained by the condition that a phenomenologically viable form of the
low energy operators of the singlet and doublet Higgs superfields is generated by the PQ breaking
sector in a way similar to the Kim-Nilles solution of the µ problem, and the resulting Higgs mass
parameters allow the electroweak symmetry breaking with small tan β. We find two minimal
models with two singlet Higgs superfields, satisfying this condition with a relatively simple form of
the PQ breaking sector, and briefly discuss some phenomenological aspects of the model.
∗
†
e-mail: shim@ibs.re.kr
e-mail: minseokseo@ibs.re.kr
1
LPN14-125, TTP14-032, IFIC/14-75
November 15, 2014
arXiv:1411.4675v1 [hep-ph] 17 Nov 2014
Forward-backward and charge asymmetries
at Tevatron and the LHC 1
¨ hn
Johann H. Ku
Institut f¨
ur Theoretische Teilchenphysik, Karlsruher Institut f¨
ur Technologie,
D-76133, Karlsruhe, GERMANY
´ n Rodrigo
Germa
Instituto de F´ısica Corpuscular, Universitat de Val`encia - Consejo Superior de
Investigaciones Cient`ıficas, Parc Cient´ıfic, E-46980 Paterna, Valencia, SPAIN
We provide a qualitative and quantitative unified picture of the charge
asymmetry in top quark pair production at hadron colliders in the SM and
summarise the most recent experimental measurements.
PRESENTED AT
8th International Workshop on the CKM Unitarity Triangle
(CKM 2014), Vienna, Austria, September 8-12, 2014
1
Work supported by the Research Executive Agency (REA) of the European Union under the
Grant Agreement number PITN-GA-2010-264564 (LHCPhenoNet), by the Spanish Government and
EU ERDF funds (grants FPA2011-23778 and CSD2007-00042 Consolider Project CPAN) and by GV
(PROMETEUII/2013/007).
Attempts at a determination of the fine-structure constant from first principles:
A brief historical overview
U. D. Jentschura1, 2 and I. N´
andori2
arXiv:1411.4673v1 [hep-ph] 17 Nov 2014
1
Department of Physics, Missouri University of Science and Technology, Rolla, Missouri 65409-0640, USA
2
MTA–DE Particle Physics Research Group, P.O.Box 51, H–4001 Debrecen, Hungary
It has been a notably elusive task to find a remotely sensical ansatz for a calculation of Sommerfeld’s electrodynamic fine-structure constant αQED ≈ 1/137.036 based on first principles. However,
this has not prevented a number of researchers to invest considerable effort into the problem, despite
the formidable challenges, and a number of attempts have been recorded in the literature. Here,
we review a possible approach based on the quantum electrodynamic (QED) β function, and on
algebraic identities relating αQED to invariant properties of “internal” symmetry groups, as well
as attempts to relate the strength of the electromagnetic interaction to the natural cutoff scale
for other gauge theories. Conjectures based on both classical as well as quantum-field theoretical
considerations are discussed. We point out apparent strengths and weaknesses of the most prominent attempts that were recorded in the literature. This includes possible connections to scaling
properties of the Einstein–Maxwell Lagrangian which describes gravitational and electromagnetic
interactions on curved space-times. Alternative approaches inspired by string theory are also discussed. A conceivable variation of the fine-structure constant with time would suggest a connection
of αQED to global structures of the Universe, which in turn are largely determined by gravitational
interactions.
PACS:
12.20.Ds (Quantum electrodynamics — specific calculations) ;
11.25.Tq (Gauge field theories) ;
11.15.Bt (General properties of perturbation theory) ;
04.60.Cf (Gravitational aspects of string theory) ;
06.20.Jr (Determination of fundamental constants) .
I.
INTRODUCTION
Today, the determination of a viable analytic formula for the fine-structure constant remains an extremely elusive
problem. The fine-structure constant αQED ≈ 1/137.036 is a dimensionless physical constant, and any conceivable
variation of it with time [1, 2] would necessarily imply a connection of electromagnetic interactions to other global
properties of the Universe, such as its age. Alternatively, one may point out that expressions for the fine-structure
constant in terms of well-defined mathematical invariants of an underlying symmetry group [3, 4] are incompatible
with a variation of the fine-structure constant with time (unless the symmetry group changes with time also). Indeed,
the problem of finding a conceivable analytic formula for the fine-structure constant is of such fundamental interest
that considerable field-theoretical insight and effort has been invested into the task, despite the formidable challenges.
It thus appears useful to review the historical development and status of these attempts, and to indicate possible
future directions of research, while noting that considerable scrutiny and scepticism are appropriate with regard to
the elusive and formidable challenge.
Let us start by recalling that the quantum electrodynamic (QED) β function [5–7] describes the evolution of the
QED running coupling αQED over different momentum scales; one may naturally ask the question if the physical value
of αQED is related to a specific momentum scale. Indeed, QED is first and foremost defined at a high-energy scale
(cutoff scale), and the renormalization-group (RG) evolution of αQED can thus be used to evolve the coupling into
the low-energy domain. If one postulates certain constraining properties of αQED either in the high-energy, or the
low-energy, limit, then one might hope [8, 9] to obtain a constraint equation which determines a physically reasonable
approximation to αQED . However, the so-called triviality of QED [10] poses a very interesting question for physicists,
namely, to explain the numerical value of αQED without having, as an “anchor point”, a “critical value” for the
coupling: From the point of view of renormalization-group (RG) theory [10], QED does not have a phase transition.
Consequences of these observations are discussed in Sec. II A.
Another intuitive ansatz for the determination of αQED would a priori involve algebraic considerations which relate
αQED to certain invariants of internal symmetry groups, e.g., those which describe the intrinsic spin of a Dirac particles.
Other attempts are based on possible connections of the QED coupling to invariants of higher-dimensional internal
symmetry groups, whose projection onto four dimensions yields a value for αQED close to the observed parameter.
Related attempts are discussed in Sec. II B.
However, one may point out that “stand-alone” approaches to the calculation of αQED , discussed in Sec. II, would
Bonn-TH-2014-16, CERN-TH-2014-231
On the two-loop corrections to the Higgs masses in the NMSSM
Mark D. Goodsell∗
1– Sorbonne Universit´es, UPMC Univ Paris 06, UMR 7589, LPTHE, F-75005, Paris, France
2– CNRS, UMR 7589, LPTHE, F-75005, Paris, France
arXiv:1411.4665v1 [hep-ph] 17 Nov 2014
Kilian Nickel†
Bethe Center for Theoretical Physics & Physikalisches Institut der Universit¨
at Bonn,
53115 Bonn, Germany
F. Staub‡
Theory Division, CERN, 1211 Geneva 23, Switzerland
Abstract
We discuss the impact of the two-loop corrections to the Higgs mass in the NMSSM beyond O(αS (αb +αt )).
For this purpose we use the combination of the public tools SARAH and SPheno to include all contributions
stemming from superpotential parameters. We show that the corrections in the case of a heavy singlet
are often MSSM-like and reduce the predicted mass of the SM-like state by about 1 GeV as long as λ is
moderately large. For larger values of λ the additional corrections can increase the SM-like Higgs mass. If
a light singlet is present the additional corrections become more important even for smaller values of λ and
can even dominate the ones involving the strong interaction. In this context we point out that important
effects are not reproduced quantitatively when only including O((αb + αt + ατ )2 ) corrections known from
the MSSM.
∗
†
‡
goodsell@lpthe.jussieu.fr
nickel@th.physik.uni-bonn.de
florian.staub@cern.ch
1
DESY 14-194
Interference effects in BSM processes
with a generalised narrow-width approximation
arXiv:1411.4652v1 [hep-ph] 17 Nov 2014
Elina Fuchs∗, Silja Thewes†, Georg Weiglein‡
DESY, Deutsches Elektronen-Synchrotron, Notkestr. 85, D-22607 Hamburg, Germany
November 19, 2014
Abstract
A generalisation of the narrow-width approximation (NWA) is formulated which allows for a
consistent treatment of interference effects between nearly mass-degenerate particles in the factorisation of a more complicated process into production and decay parts. It is demonstrated
that interference effects of this kind arising in BSM models can be very large, leading to drastic
modifications of predictions based on the standard NWA. The application of the generalised NWA
is demonstrated both at tree level and at one-loop order for an example process where the neutral Higgs bosons h and H of the MSSM are produced in the decay of a heavy neutralino and
subsequently decay into a fermion pair. The generalised NWA, based on on-shell matrix elements
or their approximations leading to simple weight factors, is shown to produce UV- and IR-finite
results which are numerically close to the result of the full process at tree level and at one-loop
order, where an agreement of better than 1% is found for the considered process. The most accurate prediction for this process based on the generalised NWA, taking into account also corrections
that are formally of higher orders, is briefly discussed.
∗
elina.fuchs@desy.de
former address
‡
georg.weiglein@desy.de
†
FERMILAB-PUB-14-477-A
A Tale of Tails: Dark Matter Interpretations of the
Fermi GeV Excess in Light of Background Model Systematics
Francesca Calore,1, ∗ Ilias Cholis,2, † Christopher McCabe,1, ‡ and Christoph Weniger1, §
1
arXiv:1411.4647v1 [hep-ph] 17 Nov 2014
2
GRAPPA, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands
Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL, 60510, USA
Several groups have identified an extended excess of gamma rays over the modeled foreground and
background emissions towards the Galactic center (GC) based on observations with the Fermi Large
Area Telescope. This excess emission is compatible in morphology and spectrum with a telltale sign
from dark matter (DM) annihilation. Here, we present a critical reassessment of DM interpretations
of the GC signal in light of the foreground and background uncertainties that some of us recently
outlaid in Calore et al. 2014. We find that a much larger number of DM models fits the gamma-ray
data than previously noted. In particular: (1) In the case of DM annihilation into ¯bb, we find that
even large DM masses up to mχ ' 74 GeV are allowed with a p-value > 0.05. (2) Surprisingly,
annihilation into non-relativistic hh gives a good fit to the data. (3) The inverse Compton emission
from µ+ µ− with mχ ∼ 60–70 GeV can also account for the excess at higher latitudes, |b| > 2◦ ,
both in its spectrum and morphology. We also present novel constraints on a large number of mixed
annihilation channels, including cascade annihilation involving hidden sector mediators. Finally,
we show that the current limits from dwarf spheroidal observations are not in tension with a DM
interpretation when uncertainties on the DM halo profile are accounted for.
I.
INTRODUCTION
Shedding light onto the origin of Dark Matter (DM) is
one of the biggest challenges of current particle physics
and cosmology. The most appealing particle DM candidates are the so-called Weakly Interacting Massive Particles (WIMP) [1–3]. Among the different indirect messengers, gamma rays play a dominant role and they have
often been defined as the golden channel for DM indirect detection (see Ref. [4] for an extensive review). The
main challenge is to disentangle putative DM signals from
the large astrophysical foregrounds and backgrounds that
are generally expected to dominate the measured fluxes.
The best example of a challenging target is the Galactic
Center (GC), where on the one hand the DM signal is expected to be brighter than anywhere else on the sky [5, 6],
but – given our poor knowledge of the conditions in the
inner Galaxy – the astrophysical foreground and background (either from Galactic point sources or from diffuse
emissions) is subject to very large uncertainties.
In this respect, it is not surprising for unmodeled
gamma-ray contributions to be found towards the inner
part of the Galaxy, above or below the expected standard
astrophysical emission. Indeed, an extended excess in
gamma rays at the GC was reported by different independent groups [7–15], using data from the Fermi Large Area
Telescope (LAT), and dubbed “Fermi GeV excess” as it
∗
†
‡
§
f.calore@uva.nl
cholis@fnal.gov
c.mcCabe@uva.nl
c.weniger@uva.nl
appears to peak at energies around 1–3 GeV. Intriguingly,
the excess emission shows spectral and morphological
properties consistent with signals expected from DM particles annihilating in the halo of the Milky Way. Recently,
the existence of a GeV excess emission towards the GC
above the modeled astrophysical foreground/background
was also confirmed by the Fermi-LAT Collaboration [16].
This revitalizes the importance of understanding the origin of this excess.
Given that the Galactic diffuse emission is maximal
along the Galactic disk and that a DM signal is expected
to be approximately spherical, the preferable region to
search for a DM annihilation signal in Fermi-LAT data
is actually a region that, depending on the DM profile,
extends between a few degrees and a few tens of degrees
away from the GC, above and below the disk [17–22].
Indeed, different groups [14, 23, 24] extracted an excess
with spectral properties similar to the GeV excess at the
GC from the gamma-ray data at higher Galactic latitudes, up to about |b| ∼ 20◦ . The extension to higher
latitudes is a critical test that the DM interpretation had
to pass, and apparently has passed.
However, when talking about excesses, a rather central question is: An excess above what? The excess
emission is defined above the astrophysical foregrounds
and backgrounds, i.e. the Galactic diffuse emission, point
sources and extended sources, modeled in the data analysis. Most previous studies of the Fermi GeV excess are
based on a small number of fixed models for the Galactic diffuse emission. These models were build for the sole
purpose of point source analyses and hence introduce uncontrollable systematics in the analysis of extended diffuse sources. In addition, since they are the result of fits
arXiv:1411.3680v1 [hep-ph] 28 Oct 2014
Review of QCD, Quark-Gluon Plasma, Heavy Quark
Hybrids, and Heavy Quark State production in p-p and
A-A collisions
Leonard S. Kisslinger1
Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
Debasish Das2,3
Saha Institute of Nuclear Physics,1/AF, Bidhan Nagar, Kolkata 700064, INDIA.
1) kissling@andrew.cmu.edu
2)dev.deba@gmail.com; 3) debasish.das@saha.ac.in
Abstract
This is a review of the Quantum Chrodynamics Cosmological Phase Transition,
the Quark-Gluon Plasma, and the detection of the Quark-Gluon Plasma via RHIC
production of heavy quark states using the mixed hybrid theory for the Ψ(2S) and
Υ(3S) states.
PACS Indices:12.38.Aw,13.60.Le,14.40.Lb,14.40Nd
Keywords: Quantum Chromodynamics,QCD Phase Transition, Quark-Gluon Plasma,
mixed hybrid theory
1
Outline of QCD Review
QCD Theory of the Strong Interaction
The QCD Phase Transition
Heavy Quark Mixed Hybrid States
Proton-Proton Collisions and Production of Heavy Quark States
RHIC and Production of Heavy Quark States
Production of Charmonium and Bottomonium States via Fragmentation
Brief Overview
2
Brief Review of Quantum Chromodynamics (QCD)
In the theory of strong interactions quarks, fermions, interact via coupling to gluons, vector
(quantum spin 1) bosons, the quanta of the strong interaction fields, color replaces the
electric charge in QED, which is why it is called Quantum Chromodynamics or QCD. See
Refs[1],[2],[3], and Cheng-Li’s book on gauge theories[4].
1
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH
CERN-PH-EP-2014-280
17 November 2014
arXiv:1411.4981v1 [nucl-ex] 18 Nov 2014
Inclusive photon production at forward rapidities in proton-proton
√
collisions at s = 0.9, 2.76 and 7 TeV
ALICE Collaboration∗
Abstract
The multiplicity and pseudorapidity distributions of inclusive photons have been measured at
√forward
rapidities (2.3 < η < 3.9) in proton-proton collisions at three center-of-mass energies, s = 0.9,
2.76 and 7 TeV using the ALICE detector. It is observed that the increase in the average photon
multiplicity as a function of beam energy is compatible with both a logarithmic and a power-law
dependence. The relative increase in average photon multiplicity produced in inelastic pp collisions
at 2.76 and 7 TeV center-of-mass energies with respect to 0.9 TeV are 37.2% ± 0.3% (stat) ± 8.8%
(sys) and 61.2% ± 0.3% (stat) ± 7.6% (sys), respectively. The photon multiplicity distributions for
all center-of-mass energies are well described by negative binomial distributions. The multiplicity
distributions are also presented in terms of KNO variables. The results are compared to model
predictions, which are found in general to underestimate the data at large photon multiplicities, in
particular at the highest center-of-mass energy. Limiting fragmentation behavior of photons has been
explored with the data, but is not observed in the measured pseudorapidity range.
c 2014 CERN for the benefit of the ALICE Collaboration.
Reproduction of this article or parts of it is allowed as specified in the CC-BY-3.0 license.
∗ See
Appendix A for the list of collaboration members
EPJ manuscript No.
(will be inserted by the editor)
An experimentalist’s view of the uncertainties in understanding
heavy element synthesis
W. Loveland
arXiv:1411.4929v1 [nucl-ex] 18 Nov 2014
Oregon State University, Corvallis, OR 97331 USA
Received: date / Revised version: date
Abstract. The overall uncertainties in predicting heavy element synthesis cross sections are examined in
terms of the uncertainties associated with the calculations of capture cross sections, fusion probabilities
and survival probabilities. Attention is focussed on hot fusion reactions. The predicted heavy element
formation cross sections are uncertain to at least one order of magnitude.
PACS. 25.70Jj Fusion and fusion-fission reactions
1 Introduction
“To deal effectively with the doubts, you should acknowledge their existence and confront them straight on, because a posture of defiant denial is self defeating” D. Kahneman [1]
The synthesis of new heavy nuclei is a topic that draws
the attention of many scientists. The challenge of adding
to the fundamental building blocks of nature, perhaps cementing one’s work for scientific eternity, is compelling.
But the experiments and their interpretation are difficult
and occasionally lead to false conclusions. A thorough understanding of the uncertainties in measurements and theory are essential for progress. In particular we must be able
to estimate the uncertainties in both experimental data
and calculated quantities from theory. We have to able to
assess the information content of a measurement and its
impact on our understanding. Measurements should test
our current theories in direct and focussed ways. Theory
should provide guidance as what the most important new
experiments should be and how the experimental data will
constrain current theories.
In this paper I review our current abilities to predict
the outcome of attempts to synthesize new heavy nuclei
using fusion reactions. I try to break down the predictions
into their component pieces (see below), i.e., the probability of getting the reacting nuclei to touch, the probability
of having the nuclei at the contact configuration evolve
inside the fission saddle point (fusion) and the probability
that the fused system will survive against the destructive fission process. I try to indicate, by comparing predictions/postdictions, with measurements related to each
of these processes, the uncertainties associated with predicting the outcome of an attempt to synthesize a new
heavy nucleus.
The remarkable recent progress in the synthesis of new
heavy and superheavy nuclei has been made using fusion
reactions. These reactions can be divided into two prototypical classes, “cold” and “hot” fusion reactions. In
“cold” fusion reactions, one bombards Pb or Bi target
nuclei with heavier projectiles (Ca-Kr) to form completely
fused systems with low excitation energies (E ∗ =10-15 MeV),
leading to a higher survival (against fission) but with a reduced probability of the fusion reaction taking place due
to the larger Coulomb repulsion in the more symmetric reacting system. In “hot” fusion reactions one uses a more
asymmetric reaction (typically involving a lighter projectile and an actinide target nucleus) to increase the fusion probability but leading to a highly excited completely
fused system (E ∗ =30-60 MeV) with a reduced probability
of surviving against fission.
Formally, the cross section for producing a heavy evaporation residue, σ EVR , in a fusion reaction can be written
as
∞
π¯h2 X
(2ℓ + 1) T (E, ℓ) PCN (E, ℓ) Wsur (E ∗ , ℓ)
2µE
ℓ=0
(1)
where E is the center of mass energy, and T(E,ℓ) is the
probability of the colliding nuclei to overcome the potential barrier in the entrance channel and reach the contact
point. (The term “evaporation residue” refers to the product of a fusion reaction followed by the evaporation of a
specific number of neutrons.) PCN is the probability that
the projectile-target system will evolve from the contact
point to the compound nucleus. Wsur is the probability
that the compound nucleus will decay to produce an evaporation residue rather than fissioning. The capture cross
section is defined as
σEV R (E) =
σcapt (E) =
∞
π¯h2 X
(2ℓ + 1) T (E, ℓ)
2µE
ℓ=0
(2)
Direct study of the alpha-nucleus optical potential at astrophysical energies using the
64
Zn(p,α)61 Cu reaction
Gy. Gy¨
urky,1, ∗ Zs. F¨
ul¨op,1 Z. Hal´
asz,1 G.G. Kiss,1 and T. Sz¨
ucs1
arXiv:1411.4827v1 [nucl-ex] 18 Nov 2014
1
Institute for Nuclear Research (Atomki), H-4001 Debrecen, Hungary
(Dated: November 19, 2014)
In the model calculations of heavy element nucleosynthesis processes the nuclear reaction rates
are taken from statistical model calculations which utilize various nuclear input parameters. It is
found that in the case of reactions involving alpha particles the calculations bear a high uncertainty
owing to the largely unknown low energy alpha-nucleus optical potential. Experiments are typically
restricted to higher energies and therefore no direct astrophysical consequences can be drawn. In the
present work a (p,α) reaction is used for the first time to study the alpha-nucleus optical potential.
The measured 64 Zn(p,α)61 Cu cross section is uniquely sensitive to the alpha-nucleus potential and
the measurement covers the whole astrophysically relevant energy range. By the comparison to
model calculations, direct evidence is provided for the incorrectness of global optical potentials used
in astrophysical models.
PACS numbers: 24.10.Ht,24.60.Dr,25.55.-e,26.30.-k
Although chemical elements heavier than Iron represent only a tiny fraction of the matter of our world, the
understanding of their stellar production mechanism remains a difficult problem of astrophysics. The bulk of
the heavy elements is thought to be produced by neutron capture reactions in the s- and r-processes [1, 2].
While the s-process is relatively well known – although
some open problems still exist –, the r-process is still very
poorly known regarding both the astrophysical site and
the nuclear physics background. The synthesis of the socalled p-isotopes – isotopes which are not produced by
the s- and r-processes – require further nucleosynthetic
processes, like the γ-process [3] or the rp-process [4].
Common in the heavy element nucleosynthesis processes is that for their modeling huge reaction networks
must be taken into account often including thousands of
reactions. With the exception of the s-process these reactions mostly involve radioactive isotopes and therefore
experimental information about these reactions is missing. Even at stable isotopes experimental data are very
scarce owing to the tiny cross section at astrophysical
energies. Consequently, reaction rates needed for the astrophysical network calculations are obtained from theoretical cross sections. In the relevant mass and energy
range the dominant reaction mechanism is the compound
nucleus formation and high level densities are encountered, the mostly used nuclear reaction theory is thus
the Hauser-Feshbach statistical model.
If the statistical model provides incorrect cross sections, then this may contribute to the failure of some
astrophysical model calculations. This is found e.g. in
the case of the γ-process where the models are typically
not able to reproduce the observed p-isotope abundances.
The problems of γ-process models triggered a huge experimental effort in the last decade aiming at the mea-
∗ Electronic
address: gyurky@atomki.mta.hu
surement of charged particle induced cross sections for
testing the statistical model predictions. Although the
experimental database is still somewhat limited and confined to the region of stable isotopes, the general observation is that statistical models strongly overestimate the
experimental (α, γ) cross sections of heavy isotopes. Deviations of up to an order of magnitude are found [3].
Owing to the steeply falling cross section towards low
energies, the cross sections are unfortunately not measured in the astrophysically relevant energy range, but
above, where cross sections typically reach at least the
µbarn range. No direct information can thus be obtained
from the measurements for the astrophysical processes,
extrapolations are inevitable which involve serious difficulties.
The cross sections from statistical models are sensitive
to various nuclear physics input parameters, like optical potentials, the γ-ray strength function, level densities, etc., which enter into the different reaction channel
widths. Detailed studies show that the cross sections
are not equally sensitive to the different widths and the
sensitivities vary strongly with energy [5]. In the case
of α-induced reactions at low, astrophysical energies the
cross sections are only sensitive to the α-width as this
width is by far the smallest owing to the Coulomb barrier penetration. At higher energies, where γ-process related experimental α-capture cross sections are available,
however, the calculations are typically also sensitive to
other widths. The simple comparison of the experimental results with model calculations therefore cannot reveal alone the incorrect nuclear input parameter. The
study of (α,n) reactions may help as the cross section of
these reactions are usually sensitive only to the α-width
[6, 7, e.g.]. The probed energy range above the neutron
threshold, however, is typically much higher than the astrophysically relevant one.
In spite of the fact that not the right energy range
is probed, modifications of the α-width obtained by the
modification of the α-nucleus optical potential are used