1. technology and computing

Efficient and robust analysis of complex scattering data under noise in
microwave resonators
S. Probst,1, a) F. B. Song,1, 2 P. A. Bushev,3 A. V. Ustinov,1, 4 and M. Weides1, 5
Physikalisches Institut, Karlsruhe Institute of Technology, D-76128 Karlsruhe,
Germany
2)
The 10th Institute of Chinese Electronic Technology Corporation, Chengdu 610036,
China
3)
Experimentalphysik, Universit¨
at des Saarlandes, D-66123 Saarbr¨
ucken, Germany
4)
Laboratory of Superconducting Metamaterials, National University of Science and Technology “MISIS”,
Moscow 119049, Russia
5)
Institut f¨
ur Physik, Johannes Gutenberg-Universit¨
at Mainz, D-55099 Mainz,
Germany
(Dated: October 14, 2014)
Superconducting microwave resonators are reliable circuits widely used for detection and as test devices for
material research. A reliable determination of their external and internal quality factors is crucial for many
modern applications, which either require fast measurements or operate in the single photon regime with small
signal to noise ratios. Here, we use the circle fit technique with diameter correction and provide a step by step
guide for implementing an algorithm for robust fitting and calibration of complex resonator scattering data
in the presence of noise. The speedup and robustness of the analysis are achieved by employing an algebraic
rather than an iterative fit technique for the resonance circle.
PACS numbers: 85.25.Hv, 07.57.Kp, 84.40.Dc
INTRODUCTION
The evaluation of the scattering parameters of resonators is crucial for a wide range of research directions.
Resonators made out of superconductors provide low
internal loss and are used to detect and study physical
systems down to the single photon regime. For instance,
in circuit quantum electrodynamics1 resonators are used
for dispersive readout or coupling to quantum objects
such as qubits2–4 or spin systems5–8 . Thus, it is crucial
to understand the physics behind these resonators
and, moreover, to be able to precisely determine their
characteristic quantities. Fitting methods for determining parameters of a resonator such as its resonance
frequency fr , coupling strength Qc or internal quality
factor Qi were studied in several publications before9–14 .
However, the high-noise environment as frequently found
in single or few photon scattering experiments imposes a
considerable challenge. In this paper, we first summarize
the resonator properties and the conventional fitting
procedures. Next, we provide a step-by-step explanation
of the circle fit method, and discuss how to subtract
the microwave environment of the resonator (cable
length, signal amplification, etc.). The robustness of this
fitting method is illustrated by adding noise to the signal.
A resonator is characterized by its resonance frequency
fr and quality factor Q. The quality factor is defined by
the ratio of the energy stored in the resonator to the average energy loss per cycle times 2π. There are usually
a) Electronic
mail: sebastian.probst@kit.edu
different energy relaxation paths, which contribute to the
quality factor. In general, internal and coupling losses
are distinguished, which are described by the internal Qi
and coupling or external Qc quality factors, respectively.
The loaded or total quality factor can be obtained by
adding up the reciprocal values of these
two
contributing
−1
quality factors11,15 Q−1
= Q−1
. As one can
i + Re Qc
l
see, the coupling quality factor can be a complex number, which will be addressed later. Resonators are usually
(b)
(a)
port 1
port 2
Qc
log(amp)
I.
f
C
R
L
Qi
phase
arXiv:1410.3365v1 [cond-mat.supr-con] 13 Oct 2014
1)
f
Figure 1. (color online) (a) An LCR resonator coupled to
transmission line. (b) Simulated transmitted amplitude and
phase signal as a function of frequency with noise.
measured either in reflection or transmission. In contrast
to a reflection measurement, it is impossible to directly
determine the internal losses of the resonator by probing
the resonator’s transmission due to the missing reference
baseline. Therefore, the reflection measurement is much
more appealing, and can be improved to choosing a so
called notch type geometry, where the resonator is coupled to a transmission line. Figure 1(a) shows such a geometry, which allows for frequency division multiplexed
readout of multiple resonators2,16–18 . The chip is measured in transmission S21 and the resonance appears as a
Observing Ultra-High Energy Cosmic Rays with Smartphones
Daniel Whiteson,1 Michael Mulhearn,2 Chase Shimmin,1 Kyle Brodie,1 and Dustin Burns2
arXiv:1410.2895v1 [astro-ph.IM] 10 Oct 2014
1
Department of Physics and Astronomy, University of California, Irvine, CA 92697
2
Department of Physics, University of California, Davis, CA
We propose a novel approach for observing cosmic rays at ultra-high energy (> 1018 eV) by repurposing the existing network of smartphones as a ground detector array. Extensive air showers
generated by cosmic rays produce muons and high-energy photons, which can be detected by the
CMOS sensors of smartphone cameras. The small size and low efficiency of each sensor is compensated by the large number of active phones. We show that if user adoption targets are met, such a
network will have significant observing power at the highest energies.
PACS numbers:
Introduction
The source of ultra-high energy cosmic rays (UHECR),
those with energy above 1018 eV, remains a puzzle even
many decades after their discovery, as does the mechanism behind their acceleration. Their high energy leaves
them less susceptible to bending by magnetic fields between their source and the Earth, making them excellent probes of the cosmic accelerators which produce
them [1, 2]. But the mechanism and location of this enormous acceleration is still not understood, despite many
theoretical conjectures [3–6].
When incident on the Earth’s atmosphere, UHECRs
produce extensive air showers, which can be detected via
the particle flux on the ground, the flourescence in the
air, or the radio and acoustic signatures. A series of
dedicated detectors [7–9] have detected cosmic rays at
successively higher energies, culminating in observation
up to 3 · 1020 eV. The flux of particles drops precipitously
above 1018 GeV, due to the suppression via interaction
with the cosmic microwave background [10, 11], making
observation of these particles challenging.
To accumulate a sufficient number of observed showers
requires either a very long run or a very large area. Constructing and maintaining a new detector array with a
large effective area presents significant obstacles. Current
arrays with large, highly-efficient devices (Auger [12],
AGASA [13]) cannot grow dramatically larger without
becoming much more expensive. Distributed detector arrays with small, cheaper devices (ERGO [14], etc) have
the potential to grow very large, but have not achieved
the size and density required to probe air showers, potentially due to the organizational obstacles of production,
distribution and maintenance of their custom-built devices.
It has been previously shown that smartphones can detect ionizing radiation [15, 16]. In this paper, we demonstrate that a dense network of such devices has power
sufficient to detect air showers from the highest energy
cosmic rays. We measure the particle-detection efficiency
of several popular smartphone models, which is necessary
for the reconstruction of the energy and direction of the
particle initiating the shower. With sufficient user adoption, such a distributed network of devices can observe
UHECRs at rates at least comparable to conventional
cosmic ray observatories. Finally, we describe the operating principles, technical design and expected sensitivity
of the CRAYFIS (Cosmic RAYs Found In Smartphones)
detector array. Preliminary applications for Android and
iOS platforms are available for testing [17].
Detection
Air showers induced by cosmic rays contain an enormous number of particles. Figure 1 shows the energy
spectrum, and spatial distribution at sea level of photons, electrons, and muons in showers as simulated by
the Corsika [18] program with the QGS-II [19] model
of hadronic interactions.
We focus our attention on photons, which have high
densities in the shower, and muons, which have excellent
penetrating power and high detection efficiency. Electrons are also numerous and have high efficiency, but may
be blocked by buildings, phone cases or camera lenses.
Heavier hadronic particles are much less common.
The sensitive element in a smartphone is the camera,
a CMOS device in which silicon photodiode pixels are
designed to absorb visible photons and convert them to
current which is collected and read out. While these devices are designed to have reasonable quantum efficiency
for visible light, the same principle allows the sensor to
detect higher-energy photons [15] as well. In the case
of muons, the photodiode is functionally equivalent to
silicon-based trackers now common in particle physics
experiments, such that the charged particle will leave
electron-hole pairs along its path.
A Geant-based simulation [20] of the energy deposition of photons in silicon indicates that the camera sensor
has efficiency over the energy range of interest (Fig. 2).
arXiv:1410.3448v1 [hep-ph] 13 Oct 2014
Transverse single-spin asymmetries in p↑ p → γX from
quark-gluon-quark correlations in the proton
K. Kanazawa1 , Y. Koike2 , A. Metz1 , and D. Pitonyak3
1 Department
of Physics, Barton Hall, Temple University, Philadelphia, PA 19122, USA
2 Department
3 RIKEN
of Physics, Niigata University, Ikarashi, Niigata 950-2181, Japan
BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973, USA
October 14, 2014
Abstract
We analyze the transverse single-spin asymmetry in direct photon production from proton-proton
collisions, denoted AγN , within collinear twist-3 factorization. We provide a calculation of the contribution due to quark-gluon-quark correlations in the unpolarized proton as well as summarize
previous studies on those effects in the polarized proton. Both soft-gluon poles and soft-fermion
poles are considered. From this complete result we then estimate AγN , including error bands due to
uncertainties in the non-perturbative inputs, at kinematics relevant for planned measurements of
this observable at the Relativistic Heavy Ion Collider. We find AγN can allow for a “clean” extraction of the Qiu-Sterman function, which could lead to a definitive solution to the so-called “sign
mismatch” crisis. Since we use the Sivers function extracted from semi-inclusive deep-inelastic scattering to develop our input for the Qiu-Sterman function, this reaction can also make a statement
about the process dependence of the Sivers function.
1
Introduction
The transverse single-spin asymmetry (TSSA) AN has been studied since the mid-1970s. Large effects
first measured in polarized lambda production at FermiLab [1] proved difficult to describe in perturbative QCD [2]. In the 1980s it was shown that quark-gluon-quark correlations in the nucleon could
lead to substantial TSSAs [3]. In the 1990s this formalism, known as collinear twist-3 factorization,
was worked out for proton-proton collisions in more detail, first for direct photon production [4, 5]
and then for pion production [6]. Several other analyses furthered the development of this framework
— see, e.g., [7–14]. In addition, this theoretical work has been complimented by many experimental
measurements of AN at proton-(anti)proton accelerators over the last two decades [15–23]. Most of
this experimental data has come in the form of light-hadron asymmetries AhN , e.g., h = π, K, η, with
the exception of the jet asymmetry Ajet
N recently measured by the AN DY Collaboration [22]. So far,
no measurement of the direct photon asymmetry AγN has been performed, although there are plans
to carry out such experiments at the Relativistic Heavy Ion Collider (RHIC) by both the PHENIX
Collaboration [24] and the STAR Collaboration [25].
At this stage we feel it is important to understand the analytical structure of the single-spin
dependent cross section for these aforementioned collinear twist-3 observables. For a general process
1
arXiv:1410.3441v1 [cs.DC] 10 Oct 2014
Heterogeneous High Throughput Scientific
Computing with APM X-Gene and Intel Xeon Phi
David Abdurachmanov1 , Brian Bockelman2 , Peter Elmer3 , Giulio
Eulisse4 , Robert Knight5 , Shahzad Muzaffar4
1
Digital Science and Computing Center, Faculty of Mathematics and Informatics, Vilnius
University, Vilnius, Lithuania
2
University of Nebraska-Lincoln
3
Department of Physics, Princeton University, Princeton, NJ 08540, USA
4
Fermilab, Batavia, IL 60510, USA
5
Research Computing, Office of Information Technology, Princeton University, Princeton,
New Jersey 08540, USA
E-mail: David.Abdurachmanov@cern.ch
Abstract. Electrical power requirements will be a constraint on the future growth
of Distributed High Throughput Computing (DHTC) as used by High Energy Physics.
Performance-per-watt is a critical metric for the evaluation of computer architectures for costefficient computing. Additionally, future performance growth will come from heterogeneous,
many-core, and high computing density platforms with specialized processors. In this paper,
we examine the Intel Xeon Phi Many Integrated Cores (MIC) co-processor and Applied
Micro X-Gene ARMv8 64-bit low-power server system-on-a-chip (SoC) solutions for scientific
computing applications. We report our experience on software porting, performance and energy
efficiency and evaluate the potential for use of such technologies in the context of distributed
computing systems such as the Worldwide LHC Computing Grid (WLCG).
1. Introduction and Motivation
Processing the data produced by High Energy Physics (HEP) experiments like those at the
Large Hadron Collider (LHC) [1] at the European Laboratory for Particle Physics (CERN)
requires significant computing resources. The scale is beyond those available in a typical single
computer center. The Worldwide LHC Computing Grid (WLCG) was established to provide the
computing resources needed for the LHC experiments, and used, for example, by the CMS and
ATLAS experiments for the discovery of the Higgs boson [2, 3]. It is a distributed computing
resource across 170 computing centers in 40 countries. The CMS experiment, for example, used
between 80,000 and 100,000 x86 64 cores from the WLCG for its processing needs in 2012.
Planned luminosity upgrades of the LHC [4] will result in a 2-3 order of magnitude increase in
dataset sizes over the next 15 years, requiring commensurate increases in processing capacity.
Intel is the leading company in general purpose server processors market. Alternative
solutions, like ARMv8 64-bit, aim to provide high-density and energy efficient platforms for
computing centers. These platforms delivered by multiple vendors are optimized for specific
market segments while ensuring compatibility by running a common instruction set, i.e. a
single ecosystem is shared. General purpose solutions provide benefits to a full software stack
arXiv:1410.3440v1 [cs.DC] 10 Oct 2014
Techniques and tools for measuring energy efficiency
of scientific software applications
David Abdurachmanov1 , Peter Elmer2 , Giulio Eulisse3 , Robert
Knight4 , Tapio Niemi5 , Jukka K. Nurminen6 , Filip Nyback6 , Gon¸
calo
Pestana5 6 , Zhonghong Ou6 , Kashif Khan 5 6
1
Digital Science and Computing Center, Faculty of Mathematics and Informatics, Vilnius
University, Vilnius, Lithuania
2
Department of Physics, Princeton University, Princeton, NJ 08540, USA
3
Fermilab, Batavia, IL 60510, USA
4
Research Computing, Office of Information Technology, Princeton University, Princeton,
New Jersey 08540, USA
5
Helsinki Institute of Physics, PO Box 64, FI-00014, Helsinki, Finland
6
Aalto University, PO Box 11100, 00076 Aalto, Finland
E-mail: goncalo.pestana@aalto.fi
Abstract. The scale of scientific High Performance Computing (HPC) and High Throughput
Computing (HTC) has increased significantly in recent years, and is becoming sensitive to total
energy use and cost. Energy-efficiency has thus become an important concern in scientific
fields such as High Energy Physics (HEP). There has been a growing interest in utilizing
alternate architectures, such as low power ARM processors, to replace traditional Intel x86
architectures. Nevertheless, even though such solutions have been successfully used in mobile
applications with low I/O and memory demands, it is unclear if they are suitable and more
energy-efficient in the scientific computing environment. Furthermore, there is a lack of tools
and experience to derive and compare power consumption between the architectures for various
workloads, and eventually to support software optimizations for energy efficiency. To that end,
we have performed several physical and software-based measurements of workloads from HEP
applications running on ARM and Intel architectures, and compare their power consumption
and performance. We leverage several profiling tools (both in hardware and software) to extract
different characteristics of the power use. We report the results of these measurements and the
experience gained in developing a set of measurement techniques and profiling tools to accurately
assess the power consumption for scientific workloads.
1. Introduction
The Large Hadron Collider (LHC) [1] at the European Laboratory for Particle Physics (CERN)
in Geneva, Switzerland, is an example of a scientific project whose computing resource
requirements are larger that those likely to provided in a single computer center. Data processing
and storage are distributed across the Worldwide LHC Computing Grid (WLCG) [2], which uses
resources from 160 computer centers in 35 countries. Such computational resources have enabled
the CMS [3] and ATLAS [4] experiments to discover the Higgs Boson [5, 6], for example. The
WLHC requires a massive amount of computational resources (250,000 x86 cores in 2012) and,
proportionally, energy. In the future, with planned increases to the LHC luminosity [7], the
FLAVOUR(267104)-ERC-86
October 14, 2014
arXiv:1410.3367v1 [hep-ph] 13 Oct 2014
News on B → K (∗)νν in the Standard Model and beyond
Jennifer Girrbach-Noe
TUM Institute for Advanced Study
Lichtenbergstr. 2a, 85748 Garching, Germany
An analysis of the rare B decays B → K (∗) νν is presented both within
the SM and beyond. The SM predictions for the branching ratios are
updated and uncertainties reduced. For the NP analysis both a model
independent approach is used and concrete NP models are studied. The
relation between b → sνν and b → s`+ `− transitions are analysed in
detail.
PRESENTED AT
Presented at the 8th International Workshop on the CKM
Unitarity Triangle (CKM 2014),
Vienna, Austria, September 8-12, 2014
1
Introduction
The decays B → K (∗) νν are theoretically very clean and will play a key role in the
tests of the SM and its extensions. They are especially sensitive to Z penguins whereas
b → s`+ `− transitions are additionally sensitive to dipole and scalar operators. Due
to their sensitivity to right-handed couplings B → K (∗) νν decays offer a powerful
test of MFV. This talk is based on [1] and studies B → K (∗) νν both within the SM
and beyond. In 2009 these decays were analysed in [2] but since the flavour precision
era is ahead of us and due to new lattice calculations and new data on b → s`+ `−
transitions it is time to have a closer look at B → K (∗) νν again. The main novelties
of [1] are:
• The SM predictions for the branching ratios and the angular observable FL are
updated. Due to new lattice calculations the form factor uncertainties decreased
considerably [3, 4].
• We exploit the SU(2)L symmetry in order to relate b → s`+ `− and b → sνν
transitions.
• New data on B → K ∗ µ+ µ− and its impact on B → K (∗) νν are included.
• We study correlations both in a model-independent approach and in concrete
models beyond the SM.
• The impact of lepton flavour non-universality is also discussed in [1] but not
covered in this talk.
2
SM results
In the SM only one operator contributes to B → K (∗) νν:
4 GF
e2
SM
= − √ Vtb Vts∗ CLSM OL + h.c. , OL =
Heff
(sγµ PL b)(νγ µ (1 − γ5 )ν)
16π 2
2
CLSM = −Xt /s2w , Xt = 1.469 ± 0.017
(1a)
(1b)
and its Wilson coefficient CLSM is known very precisely (including NLO QCD corrections [5, 6, 7] and two-loop electroweak contributions [8]). The form factors for the
exclusive decays B → K (∗) νν have to be calculated by means of non-perturbative
methods. Great progress has been made by lattice calculation, especially at large q 2
[3, 4]. At low q 2 the results from light-cone sum rules are used [9, 10]. Further details
can be found in [1] and the rescaled form factors are shown there in appendix A.
1
SLAC-PUB-16101, SMU-HEP-14-08
Top-quark forward-backward asymmetry in e+ e− annihilation at NNLO in QCD
Jun Gao1, 2, ∗ and Hua Xing Zhu3, †
1
Department of Physics, Southern Methodist University, Dallas, TX 75275-0175, USA
High Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
3
SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94309, USA
arXiv:1410.3165v1 [hep-ph] 12 Oct 2014
2
We report on a complete calculation of electroweak production of top quark pairs in e+ e− annihilation at next-to-next-to-leading order in Quantum Chromodynamics. Our setup is fully differential
and can be used to calculate any infrared-safe observable. Especially we calculated the next-to-nextto-leading order corrections to top-quark forward-backward asymmetry and found sizable effects.
Our results show a large reduction of the theoretical uncertainties in predictions of the forwardbackward asymmetry, and allow a precision determination of the top quark electroweak couplings
at future e+ e− colliders.
Introduction. Top-antitop quark pairs can be copiously
produced at future International Linear Collider (ILC),
facilitating a detailed study of top quark properties [1].
The clean enviorement of lepton collider allows measurement of the process e+ e− → tt¯ to very high accuracy,
which also demands high precision in theoretical calculation, in particular the inclusion of higher order QCD
radiative corrections. In the past, significant theoretical
efforts have been focused on tt¯ production at threshold,
for which Next-to-Next-to-Leading Order (NNLO) QCD
corrections are known for more than a decade [2], and
even next-to-next-to-next-to-leading order QCD corrections will be available in the near future [3]. However, for
tt¯ production in the continuum only total cross sections
are known in high energy expansion [4]. Ingredients for
a fully differential NNLO calculation in the continuum
have been obtained by different groups [5, 6]. Recently,
we reported a fully differential NNLO calculation for the
photon mediated contributions [7], using a NNLO generalization of phase space slicing method [8, 9]. 1 In this
Letter, we complete this calculation by including also the
SM Z boson contributions.
As an important application of our results, we consider
the calculation of top-quark forward-backward asymmetry (AF B ) at NNLO in e+ e− collision in the continuum.
In the limit of small top quark mass, this observable has
been computed to NNLO in refs. [12]. The full mass effects are only known for the pure two-loop virtual contributions [13]. We report in this Letter the first calculation
of full NNLO QCD corrections to this observable, including both loop contributions and real-radiation contributions. AF B is an important precision observable for the
determination of neutral-current electroweak couplings of
top quark with photon and Z boson. Their precise measurement is an important probe of physics beyond Standard Model, e.g. Randall-Sundrum models [14], models
of compositeness [15]. The information of top quark neu-
1
Independently, calculation of inclusive cross section for e+ e− →
γ ∗ → tt¯ at NNLO based on massive generalization of antenna
subtraction method [10] has been reported recently in ref. [11].
tral coupling is encoded in the top-quark form factor. For
on-shell tt¯ pair, the form factor can be expressed by four
independent scalar form factors,
h V
2
V
2
F
(Q
)
+
γ
F
(Q
)
ΓttV
(Q
)
=
−ie
γ
5 1a
µ
µ
1v
µ
σµν ν
V
V
+
(Q2 ) + γ5 F2a
(Q2 )
(1)
Q iF2v
2mt
where Qµ is the total four-momentum of tt¯, e is the
positron charge, and mt is the top-quark mass. V denotes photon (γ) or Z boson. To Leading Order (LO) in
electroweak theory and QCD, the vector and axial form
V
V
factors, F1v
(Q2 ) and F1a
(Q2 ), are given respectively by
γ
F1v
= Qt ,
Z
F1v
=
1
sin 2ϑ
γ
F1a
=0,
1
−1
Z
− 2Qt sin2 ϑ , F1a
=
(2)
2
2 sin 2ϑ
Qt = 2/3 is the top-quark charge in unit of e, and ϑ is
the weak-mixing angle. At ILC the top-quark forwardbackward asymmetry can be measured to a precision
of about one percent in relative, through both the full
hadronic or semi-leptonic channels [16–18]. Correspondingly the above form factors will be determined much
more precisely as compared to at the LHC [17], and thus
provides strong sensitivity to any new physics that could
modify the top-quark electroweak couplings. In this Letter, we computed the NNLO QCD corrections to the fully
differential production of top quark pair, thereby obtain
the AF B at NNLO for the first time. Our calculation
provides the most precise predictions on AF B including
its theoretical uncertainties, and also allows corrections
for experimental acceptance using the full kinematic information.
The formalism. A fully differential calculation for
e+ e− → tt¯ at NNLO in QCD involves three types of diagrams, namely the two-loop virtual diagrams, one-loop
real-virtual diagrams, and double real-emission diagrams.
The individual contributions of these diagrams are known
for some time, but combining them in a consistent way is
a non-trivial task due to the presence of infrared singularities in QCD matrix elements. To this end, we employ
arXiv:1410.3259v1 [hep-ex] 13 Oct 2014
An automated framework for hierarchical
reconstruction of B mesons at the Belle II experiment
C Pulvermacher, T Keck, M Feindt, M Heck and T Kuhr
Institut f¨
ur Experimentelle Kernphysik, Karlsruhe Institute of Technology (KIT),
Wolfgang-Gaede-Str. 1, 76131 Karlsruhe, DE
E-mail: christian.pulvermacher@kit.edu
Abstract.
We present a software framework for Belle II that reconstructs B mesons in many decay
modes with minimal user intervention. It does so by reconstructing particles in user-supplied
decay channels, and then in turn using these reconstructed particles in higher-level decays.
This hierarchical reconstruction allows one to cover a relatively high fraction of all B decays by
specifying a limited number of particle decays. Multivariate classification methods are used to
achieve a high signal-to-background ratio in each individual channel. The entire reconstruction,
including the application of pre-cuts and classifier trainings, is automated to a high degree and
will allow users to retrain to account for analysis-specific signal-side selections.
1. Introduction
Belle II is an experiment being built at the e+ e− SuperKEKB B factory in Tsukuba, Japan,
and is planned to have a luminosity 40 times higher than its predecessor Belle [1]. Like
other B factories the collider will operate mainly on the Υ(4S) resonance, which decays with
> 96 % branching ratio into pairs of B mesons. Since these events consist of only B + B − or
¯ 0 pairs and their decay products—with only minor contamination from beam or electronics
B0B
background—they enable the use of reconstruction techniques that would not be available at a
hadron collider.
Specifically, reconstructing one B meson (called Btag ) allows one to infer information about
the other B, including its four-momentum, without explicitly reconstructing it. Combined with
a signal selection, the additional information about Bsig allows to improve the reconstruction,
e.g. in channels with neutrinos. Additionally, one can also make use of the fact that in a correctly
reconstructed event every track must come from one of the B mesons, so requiring the absence
of additional tracks improves the purity of the selection. This is equivalent to reconstructing
the Υ(4S), but of course requires a high efficiency in the Btag reconstruction to be of use.
2. Hierarchical reconstruction
To this end, a neural-network-assisted reconstruction of B mesons in many decay channels was
pioneered at the Belle experiment which reconstructs decays of particles into their immediate
daughters and combines the output until reaching the B meson level [2]. To reduce the
computational burden imposed by the combinatorics of the reconstruction, soft cuts based on
the network output remove background at each stage without overly compromising efficiency.
The Higgs Physics Programme
at the International Linear Collider
Felix Sefkow1
1
DESY, Notketraße 85, 22607 Hamburg, Germany
arXiv:1410.3246v1 [hep-ex] 13 Oct 2014
DOI: will be assigned
The talk summarises the case for Higgs physics in e+ e− collisions and explains how Higgs
parameters can be extracted in a model-independent way at the International Linear Collider (ILC). The expected precision will be discussed in the context of projections for the
experiments at the Large Hadron Collider (LHC).
1
Introduction
The discovery of a Higgs boson, honoured with the 2013 Nobel prize in physics, marks a turning
point in particle physics, as the last missing building block of the Standard Model falls into place
and opens the door to completely new studies of a particle unlike every other discovered before.
Like in many earlier instances in the history of particle physics, it did not come as a surprise, but
was anticipated and sought for. The Higgs mass had been predicted with increasing precision
from the analysis of electro-weak quantum corrections, in which measurements at the previous
generation of e+ e− colliders played a prominent rˆole.
Today, Higgs physics has been identified as one of the prime ”drivers” of the field, as a
compelling line of research with great promise, where surprises may be expected. The main
question is to fully establish the profile of the Higgs particle, measure its quantum numbers
and, above all, its precisely predicted couplings to almost all other fundmental particles, and
to find out whether it fulfils its rˆ
ole in the Standard Model, or whether it holds the key to new
physics beyond.
The accuracy, which is required in order to detect possible mechanisms behind electroweak
symmetry breaking through deviations of the Higgs couplings from their pure Standard Model
values, has been quantitatively investigated in the framework of the Snowmass study 2013 [1].
Popular models like two-Higgs doublet or composite Higgs schemes, which predict new particles
at the TeV scale, and which are still compatible with recent limits from direct searches at the
LHC, typically lead to such deviations in the per-cent or sub-percent range. This sets the scale
of the future experimental challenges and demonstrates the discovery potential of precision
measurements in the Higgs sector.
The ILC and its detectors
The ILC has been proposed as the next big high energy accelerator project. It is designed to
have centre-of-mass energies ranging from 250 to 500 GeV and is upgradeable to reach 1 TeV.
The delivered luminosity increases with energy and amounts to typically 100 – 300 fb−1 /y,
PANIC14
1
π
Determination of f+
(0) and Extraction of |Vcd | from Semileptonic D Decays
G. Rong, Y. Fang, H. L. Ma, and J. Y. Zhao
arXiv:1410.3232v1 [hep-ex] 13 Oct 2014
Institute of High Energy Physics, Beijing 100039, People’s Republic of China
(Dated: October 14, 2014)
By globally analyzing all existing measured branching fractions for D → πe+ νe decays, partial
decay rates in different four momentum transfer-squared q 2 bins, as well as products of the decay
π 2
form factor f+
(q ) and the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix element |Vcd |,
π
we obtain f+ (0)|Vcd | = 0.1428 ± 0.0019. This product, in conjunction with |Vcd | from a global
π
Standard Model fit, implies a value for the D → π semileptonic form factor f+
(0) = 0.634 ± 0.008 ±
0.002, which is consistent within error with those calculated in theory based on QCD, but with
π
higher precision than the most accurate f+
(0)LQCD = 0.666 ± 0.020 ± 0.021 calculated in LQCD
by a factor of 3.3. Alternately, using this product together with the most accurate form factor
+
calculated in LQCD, we find |Vcd |D→πe νe = 0.2144 ± 0.0029exp ± 0.0093LQCD . Combining this
+
+
+
|Vcd |D→πe νe together with |Vcd |D →µ νµ = 0.2160 ± 0.0049 ± 0.0014 extracted from both the
BESIII and CLEO-c measurements of D+ → µ+ νµ decays, we find the most precisely extracted
|Vcd | to be |Vcd | = 0.2157 ± 0.0045 up to date, which improves the accuracy of the PDG’2014 value
|Vcd |PDG′ 2014 = 0.225 ± 0.008 by over 70%. Using this |Vcd | together with the PDG’2014 |Vud | and
|Vtd |, we check for first column unitarity and find |Vud |2 + |Vcd |2 + |Vtd |2 − 1 = −0.004 ± 0.002, which
π
deviates from unitarity by 2σ. In addition, we find the ratio of f+
(0) and D+ decay constant fD +
π
to be f+
(0)/fD + = (3.11 ± 0.08) GeV−1 , which can be used to validate LQCD calculations for these
two quantities.
I.
INTRODUCTION
In the Standard Model (SM) of particle physics, the
mixing between the quark flavors in weak interaction
is parameterized by the Cabibbo-Kobayashi-Maskawa
(CKM) matrix VˆCKM , which is a 3 × 3 unitary matrix.
Since the CKM matrix elements are fundamental parameters of the SM, they should be measured as accurately
as possible. Precise measurements of these elements are
very important in testing the SM and searching for New
Physics (NP) beyond the SM. Any improved measurement of these elements would be the important input for
precision test of the SM.
Three generation unitarity can be checked to see
†
whether VˆCKM ∗ VˆCKM
= Iˆ is satisfied, which leads to
test first, second and third column/row unitarity. The
unitarity also gives rise to unitarity triangle (UT) rela∗
tion Vud Vub
+ Vcd Vcb∗ + Vtd Vtb∗ = 0. To check for this
column/row unitarity and the UT relation, many experimental measurements and theoretical efforts have been
made in flavor physics for many years. If any of these
consistency checks significantly deviate from unitarity, it
may indicate some evidence for NP effects.
Each matrix element can be extracted from measurements of different processes supplemented by theoretical
calculations for corresponding hadronic matrix elements.
Since the effects of strong interactions and weak interaction can be well separated in semileptonic D decays, these
decays are excellent processes from which one can determine the magnitude of the CKM matrix element Vcd(s) .
In the SM, neglecting the lepton mass, the differential
decay rate for D → πe+ νe process is given by
dΓ
G2F
π 2 2
=
X
|Vcd |2 p3 |f+
(q )| ,
dq 2
24π 3
(I.1)
where GF is the Fermi constant, p is the three momentum of the π meson in the rest frame of the D meson, q 2
is the four momentum transfer-squared, i.e. the invariπ 2
ant mass of the lepton and neutrino system, and f+
(q )
is the form factor which parameterizes the effect of strong
interaction in the decay. In Eq. (I.1), X is a multiplicative factor due to isospin, which equals to 1 for mode
D0 → π − e+ νe and 1/2 for mode D+ → π 0 e+ νe .
In addition to extraction of |Vcd |, precise measurements
of the D → π semileptonic form factor is also very important to validate the lattice QCD (LQCD) calculation of
the form factor. If the LQCD calculation of the form factor pass the test with the precisely measured form factor
of D → πe+ νe decay, the uncertainty of the semileptonic
B decay form factor calculated in LQCD would be reduced. This would help in reducing the uncertainty of
the measured |Vub | from semileptonic B decays [1]. The
improved measurement of |Vub | from semileptonic B decay will improve the determination of the Bd UT, from
which one can more precisely test the SM and search for
NP beyond the SM.
In the past decades, copious measurements of decay
branching fractions and/or decay rates for D → πe+ νe
were performed at different experiments. To obtain the
π
knowledge about f+
(0) and |Vcd | as better as possible, we
analyze all of these existing measurements. By a comprehensive analysis of these existing measurements together
with |Vcd | from a global SM fit or together with the form
π
factor f+
(0) calculated in LQCD, we precisely determine
π
f+ (0) and extract |Vcd |.
π
In this article, we report the determination of f+
(0)
and extraction of |Vcd | by analyzing all of these existing
measurements of the semileptonic D → πe+ νe decays
in conjunction with |Vcd | from a global SM fit or with
π
the form factor f+
(0) calculated in LQCD. In the follow-
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–6
Elastic Z 0 production at HERA
L. Stanco, on behalf of the ZEUS Collaboration
arXiv:1410.3229v1 [hep-ex] 13 Oct 2014
INFN–Padova, Via Marzolo, 8 I-35131 Padova, Italy
Abstract
The production of Z 0 bosons in the reaction ep → eZ 0 p(∗) , where p(∗) stands for a proton or a low-mass nucleon
resonance, has been studied in ep collisions at HERA using the ZEUS detector. The analysis is based on a data
sample collected between 1996 and 2007, amounting to 496 pb−1 of integrated luminosity. The Z 0 was measured in
the hadronic decay mode. The elasticity of the events was ensured by a cut on ηmax < 3.0, where ηmax is the maximum
pseudorapidity of energy deposits in the calorimeter defined with respect to the proton beam direction.
A signal was
observed at the Z 0 mass. The cross section of the reaction ep → eZ 0 p(∗) was measured to be σ ep → eZ 0 p(∗) =
0.13 ± 0.06 (stat.) ± 0.01 syst. pb, in agreement with the Standard Model prediction of 0.16 pb. This is the first
measurement of Z 0 production in ep collisions. In this paper we report the already published ZEUS result by adding
the sensitivities of the most recent similar results from CMS and ATLAS.
Keywords: e–p interactions, Z0 boson
1. Introduction
The production of electroweak bosons in ep collisions is a good benchmark process for testing the Standard Model (SM). Even though the expected numbers
of events for W ± and Z 0 production are low, the measurement of the cross sections of these processes is important as some extensions of the SM predict anomalous couplings and thus changes in these cross sections. A measurement of the cross section for W ±
production at HERA has been performed by H1 and
ZEUS [2] in events containing an isolated lepton and
missing transverse momentum, giving a cross section
σ (ep → W ± X) = 1.06 ± 0.17 stat. ⊕ syst. pb, in good
agreement with the SM prediction. The cross section
for Z 0 production is predicted to be 0.4 pb.
This paper reports on a measurement of the production of Z 0 bosons in e± p collisions using an integrated
luminosity of about 0.5fb−1 . The hadronic decay mode
was chosen1 because of its large branching ratio. The
1 The Z 0 decay into charged lepton pairs was studied in a previous
ZEUS publication [3].
excellent resolution of the ZEUS hadronic calorimeter
makes this measurement possible. The analysis was
restricted to elastic and quasi-elastic Z 0 production in
order to suppress QCD multi-jet background. The selected process is ep → eZ 0 p(∗) , where p(∗) stands for
a proton (elastic process) or a low-mass nucleon resonance (quasi-elastic process).
The corresponding and final result has been already
published by the ZEUS Collaboration in [1] which content corresponds to this report with the addition of LHC
comparison.
Fig. 1 shows a leading-order (LO) diagram of Z 0 production with subsequent hadronic decay. In such events,
there are at least two hadronic jets with high transverse
energies, and no hadronic energy deposits around the
forward2 direction, in contrast to what would be ex2 The ZEUS coordinate system is a right-handed Cartesian system,
with the Z axis pointing in the proton beam direction, referred to as
the forward direction, and the X axis pointing towards the centre of
HERA. The coordinate origin is at the
interaction point. The
nominal
pseudorapidity is defined as η = − ln tan 2θ , where the polar angle, θ,
is measured with respect to the proton beam direction.
Study of the process e+ e− → n¯
n at the VEPP-2000 e+ e− collider with the SND
detector
M. N. Achasov,1, 2 A. Yu. Barnyakov,1, 2 K. I. Beloborodov,1, 2 A. V. Berdyugin,1, 2 D. E. Berkaev,1, 2
A. G. Bogdanchikov,1 A. A. Botov,1 T. V. Dimova,1, 2 V. P. Druzhinin,1, 2 V. B. Golubev,1, 2 L. V. Kardapoltsev,1, 2
A. S. Kasaev,1 A. G. Kharlamov,1, 2 A. N. Kirpotin,1 I. A. Koop,1, 2, 3 A. A. Korol,1, 2 S. V. Koshuba,1, 2
D. P. Kovrizhin,1, 2 A. S. Kupich,1, 2 K. A. Martin,1, 2 A. E. Obrazovsky,1 E. V. Pakhtusova,1 Yu. A. Rogovsky,1, 2
A. I. Senchenko,1 S. I. Serednyakov,1, 2, ∗ Z. K. Silagadze,1, 2 Yu. M. Shatunov,1, 2 D. A. Shtol,1
D. B. Shwartz,1, 2 A. N. Skrinsky,1 I. K. Surin,1 Yu. A. Tikhonov,1, 2 Yu. V. Usov,1, 2 and A. V. Vasiljev1, 2
arXiv:1410.3188v1 [hep-ex] 13 Oct 2014
1
Budker Institute of Nuclear Physics, SB RAS, Novosibirsk, 630090, Russia
2
Novosibirsk State University, Novosibirsk, 630090, Russia
3
Novosibirsk State Technical University, Novosibirsk, 630092, Russia
The process e+ e− → n¯
n has been studied at the VEPP-2000 e+ e− collider with the SND detector
in the energy range from threshold up to 2 GeV. As a result of the experiment, the e+ e− → n¯
n
cross section and effective neutron form factor have been measured.
PACS numbers: 13.66.Bc, 13.20.Gd, 13.40.Hq, 14.40.Be
I.
INTRODUCTION
Nucleons (neutron and proton) are the subject of theoretical and experimental studies for many decades. Their
internal structure can be described in terms of the electromagnetic form factors, electric GE and magnetic GM , which
are complex functions of the momentum transfer squared. To measure the nucleon timelike form factors, the reactions
¯ cross section, where B is a spin-1/2 baryon with the mass
e+ e− → p¯
p, n¯
n and p¯
p → e+ e− are used. The e+ e− → B B
mB , is given by the following expression:
1
α2 βC
dσ
|GM (s)|2 (1 + cos2 θ) + |GE (s)|2 sin2 θ ,
(s, θ) =
(1)
dΩ
4s
τ
p
where s = 4Eb2 , Eb is the beam energy, β = 1 − 4m2B /s, C is a factor taking into account Coulomb interaction of
the final baryons [C = y/(1 − e−y ) with y = πα(1 + β 2 )/β for protons [1], and C = 1 for neutrons], τ = s/4m2B , and
θ is the baryon polar angle in the e+ e− center-of-mass (c.m.) frame. At the threshold |GE | = |GM |. The total cross
section has the following form:
1
4πα2 βC
|GE (s)|2 .
σ(s) =
|GM (s)|2 +
(2)
3s
2τ
From the measurement of the total cross section the linear combination of squared form factors
F (s)2 =
2τ |GM (s)|2 + |GE (s)|2
2τ + 1
(3)
can be determined. The function F (s) is called the effective form factor. It is this function that is measured in most of
e+ e− and p¯
p experiments. The |GE /GM | ratio can be extracted from the analysis of the measured cos θ distribution
(see Eq.(1)).
The proton timelike form factor was studied in many experiments. The most precise measurement of the e+ e− → p¯
p
cross section in the energy region of interest was performed in the BABAR experiment [2]. For the ratio of the proton
timelike form factors |GE /GM | there are two measurements, BABAR [2] and PS170 [3], which contradict to each other.
For neutron, the only measurement of the e+ e− → n¯
n cross section was performed in the FENICE experiment [4],
and there are no data on the |GE /GM | ratio.
In this work we present results on the neutron form factor in the c.m. energy range from threshold up to 2 GeV.
The experiment has been carried out at the VEPP-2000 e+ e− collider [5] with the SND detector [6] in Novosibirsk.
∗ e-mail:seredn@inp.nsk.su
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP/2014-234
2014/10/14
CMS-FSQ-12-035
arXiv:1410.3153v1 [hep-ex] 12 Oct 2014
Measurement of electroweak production of two jets in
association with a Z boson
√ in proton-proton collisions at
s = 8 TeV
The CMS Collaboration∗
Abstract
The purely electroweak (EW) cross section for the
√production of two jets in association
with a Z boson, in proton-proton collisions at s = 8 TeV, is measured using data
recorded by the CMS experiment at the CERN LHC, corresponding to an integrated
luminosity of 19.7 fb−1 . The electroweak cross section for the ``jj final state (with ` = e
or µ and j representing the quarks produced in the hard interaction) in the kinematic
region defined by M`` > 50 GeV, Mjj > 120 GeV, transverse momentum pTj > 25 GeV,
and pseudorapidity |ηj | < 5, is found to be σEW (``jj) = 174 ± 15 (stat) ± 40 (syst) fb,
in agreement with the standard model prediction. The associated jet activity of the
selected events is studied, in particular in a signal-enriched region of phase space,
and the measurements are found to be in agreement with QCD predictions.
Submitted to the European Physical Journal C
c 2014 CERN for the benefit of the CMS Collaboration. CC-BY-3.0 license
∗ See
Appendix A for the list of collaboration members
arXiv:1410.3045v1 [hep-ex] 12 Oct 2014
PRODUCTION OF SINGLE TOP QUARK - RESULTS FROM THE
TEVATRON AND THE LHC
CHANG-SEONG MOON
AstroParticule et Cosmologie, Universit´e Paris Diderot, CNRS/IN2P3,
10, rue Alice Domon et L´eonie Duquet 75205 Paris, France
and INFN Sezione di Pisa, Largo B. Pontecorvo, 3, 56127 Pisa, Italy
We present the most recent measurements of single top quark production cross section by
the CDF and D0 experiments at the Fermilab Tevatron Collider and the ATLAS and CMS
experiments at the Large Hadron Collider (LHC). The data were collected at the Tevatron
corresponding to an integrated luminosity of up to 9.7 fb−1 of proton-antiproton (p¯
p) collisions at a centre-of-mass energy of 1.96 TeV and at the LHC corresponding to an integrated
luminosity of up to 4.9 fb−1 of proton-proton (pp) collisions at a centre-of-mass energy of 7
TeV in 2011 and up to 20.3 fb−1 at a centre-of-mass energy of 8 TeV in 2012. The measurements of single top quark production in s-channel, t-channel and associated production of a
top quark and a W -boson (tW production) are presented separately and lower limits on the
CKM matrix element |Vtb | from the single top quark cross section are set.
1
Introduction
Top quarks are predominantly produced in pairs via the strong interaction in pp or p¯
p collisions
but they can be also are produced singly via the electroweak interaction. The Standard Model
(SM) predicts three single top quark processes which are t-channel, s-channel and associated
production of a top quark and a W -boson which are shown in Figure 1. Main challenge to
observe the single top process, is to overcome large background for extraction of the single top
signal. The single top quark production was first observed by the CDF 1 and D0 2 experiments
at the Tevatron in 2009. Recently many new results on the single top production have been
reported from the Tevatron and the LHC. We will summarize and discuss the most important
results on the ATLAS, CDF, CMS and D0 experiments in this paper.
2
Physics Motivation
Single top production is an important background for the SM Higgs boson production but
also physics process to test the SM prediction via directly measuring the CKM matrix element
|Vtb |. Any excess of |Vtb | over the SM prediction indicates the presence of new physics process
LPT Orsay 14-74
DAMTP-2014-56
Pion couplings to the scalar B meson
Benoˆıt Blossier,1 Nicolas Garron† ,2 and Antoine G´erardin1, 3
arXiv:1410.3409v1 [hep-lat] 13 Oct 2014
1
Laboratoire de Physique Th´eorique∗ , CNRS et Universit´e Paris-Sud XI, Bˆ
atiment 210, 91405 Orsay Cedex, France
2
Department of Applied Mathematics & Theoretical Physics,
University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom
3
Laboratoire de Physique Corpusculaire de Clermont-Ferrand‡ , Campus des C´ezeaux,
24 avenue des Landais, BP 80026, 63171 Aubi`ere Cedex, France
We present two-flavor lattice QCD estimates of the hadronic couplings gB0∗ Bπ and gB1∗ B0∗ π that
parametrise the non leptonic decays B0∗ → Bπ and B1∗ → B0∗ π. Our framework is the Heavy Quark
Effective Theory (HQET) in the static limit and solving a Generalized Eigenvalue Problem (GEVP)
reveals crucial to disentangle the B0∗ (B1∗ ) state from the Bπ(B ∗ π) state. This work brings us
some experience on how to treat the possible contribution from multihadronic states to correlation
functions calculated on the lattice, especially when S-wave states are involved.
PACS numbers: 12.39.Fe, 12.39.Hg, 13.25.Hw, 11.15.Ha.
I.
INTRODUCTION
Heavy Meson Chiral Perturbation Theory (HMχPT) [1, 2] is commonly used to extrapolate lattice data
in the heavy-light sector to the physical point. Relying on Heavy Quark Symmetry and the (spontaneously
broken) chiral symmetry, an effective Lagrangian is derived where heavy-light mesons fields [3] couple to
a Goldstone field via derivative operators. In the static limit, the total angular momentum of the light
~ is conserved independently of the total angular momentum J = jl ± 1/2.
degrees of freedom, ~jl = ~sl + L,
The pseudoscalar (B) and the vector (B ∗ ) mesons belong to the doublet jlP = (1/2)− corresponding to
L = 0 whereas the scalar (B0∗ ) and the axial (B1∗ ) mesons belong to the positive parity doublet jlP = (1/2)+
corresponding to L = 1 (see Table I). Equivalently to the low energy constants that parametrize the well
known chiral Lagrangian, hadronic couplings enter the effective theory under discussion, that is particularly
suitable to describe processes with emission of soft pions, i.e. H1 (J1 ) → H2 (J2 )π where Hi is a heavy-light
meson, and pπ Λχ ∼ 1 GeV. The associated pionic couplings are gH1 (J1 )H2 (J2 )π and they cannot be
computed in perturbation theory. When the negative j P = (1/2)− and positive j P = (1/2)+ parity states
are taken into account, the effective Lagrangian is parametrized by three couplings gˆ, g˜ and h. The first
L
jlP
JP
−
state
0
(1/2)−
0
1−
B
B∗
1
(1/2)+
0+
1+
B0∗
B1∗
TABLE I: Quantum numbers of the ground state B meson and its first orbital excitations.
†
∗
‡
On leave from School of Mathematics, Trinity College, Dublin 2, Ireland
Unit´
e Mixte de Recherche 8627 du Centre National de la Recherche Scientifique
Unit´
e Mixte de Recherche 6533 CNRS/IN2P3 – Universit´
e Blaise Pascal
Photon Emission from a Momentum Anisotropic Quark-Gluon Plasma
Chun Shen,1, 2, ∗ Jean-Fran¸cois Paquet,1 Ulrich Heinz,2 and Charles Gale1, 3
1
arXiv:1410.3404v1 [nucl-th] 13 Oct 2014
Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8, Canada
2
Department of Physics, The Ohio State University, Columbus, Ohio 43210-1117, USA
3
Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, D-60438 Frankfurt am Main, Germany
(Dated: October 14, 2014)
We compute the photon emission rate from a quark-gluon plasma with an anisotropic particle
momentum distribution induced by a non-vanishing local shear pressure tensor. Our calculation
includes photon production through Compton scattering and quark-antiquark annihilation at leading
order in αs , with all off-equilibrium corrections to leading order in the momentum anisotropy. For
fermions we prove that the Kubo-Martin-Schwinger (KMS) relation holds in the hard loop regime
for any particle momentum distribution function that is reflection-symmetric. This supports the
equivalence, for 2 to 2 scattering processes, of the diagrammatic and kinetic approaches to calculating
the photon emission rate. We compare the viscous rates from these two approaches at weak and
realistic coupling strengths and provide parameterizations of the equilibrium and viscous photon
emission rates for phenomenological studies in relativistic heavy-ion collisions.
PACS numbers:
I.
INTRODUCTION
Heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) offer
a privileged window for studying the physics of hot and dense strongly interacting matter. The smallness of the
electromagnetic coupling constant and small extent of the hot QCD medium produced in heavy-ion collisions makes
the latter largely transparent to electromagnetic probes such as thermal photons and dileptons. This is to be contrasted
with the very small mean free path of colored particles in the medium. This difference means that, through their
production rates in the medium, electromagnetic probes can provide information about the entire space-time evolution
of the QCD medium that is not subsequently scrambled by further interactions.
Controlled calculations of the rate of photon production from a hot QCD medium are possible only in certain
limiting situations. For a perfectly thermalized, weakly-coupled (gs 1) quark gluon plasma (QGP) a complete
calculation of the rate at O(e2 gs2 ) has been available for a decade [1]. The next-to-leading-order correction O(e2 gs3 )
to the thermal photon rate was computed recently [2]. At temperatures below the pseudocritical temperature for
the quark-hadron phase transition, Tc ∼ 155−165 MeV, where dense QCD matter is modeled as a hadron resonance
gas, effective Lagrangian approaches have been adopted [3]. Those calculations assume that the medium is static,
homogeneous, and fully thermalized.
The success of hydrodynamical descriptions of the hot QCD medium created in heavy ion collisions [4, 5] makes it
reasonable to assume that the medium is not too far from local thermal equilibrium. However, non-zero values for
its transport coefficients, resulting from non-zero mean free paths of the constituents, lead to deviations from local
thermal equilibrium in an expanding system which increase with the expansion rate. For example, in an anisotropically
expanding system shear viscosity causes the momentum distribution in the local rest frame to become anisotropic
itself, falling off more steeply in the directions into which the system expands more rapidly.
A number of attempts have been made at evaluating the consequences of such off-equilibrium effects on the (virtual)
photon emission rates in a QGP [6–8]. However, these previous works all share one shortcoming: for a given collision
process that results in the emission of a photon, they include the viscous corrections to the local momentum distribution
functions only for the incoming and outgoing particles, but ignore viscous medium modifications of the collision
matrix element itself. For scattering processes in which the inclusion of medium effects is essential (for example,
when dynamical mass generation for the medium constituents serves as a regulator for infrared divergences associated
with otherwise massless particle exchange) viscous corrections to the distribution functions can lead to significant
modifications of the screening mechanism and therefore to the collision matrix element. This problem was first
tackled in [9–11] for simple parameterizations of the local momentum anisotropy.
∗ Corresponding
author: chunshen@physics.mcgill.ca
Charm and strange quark masses and fDs from overlap fermions
Yi-Bo Yang1,2 , Ying Chen1 , Andrei Alexandru3 , Shao-Jing Dong2 , Terrence Draper2 ,
Ming Gong1,2 , Frank X. Lee3 , Anyi Li4 , Keh-Fei Liu2 , Zhaofeng Liu1 , and Michael Lujan3
(χQCD Collaboration)
arXiv:1410.3343v1 [hep-lat] 13 Oct 2014
1
Institute of High Energy Physics and Theoretical Physics Center for Science Facilities,
Chinese Academy of Sciences, Beijing 100049, China
2
Department of Physics and Astronomy,
University of Kentucky, Lexington, KY 40506, USA
3
Department of Physics, George Washington University,
Washington, DC 20052, USA
4
Institute for Nuclear Theory,
University of Washington, Seattle, WA 98195, USA
We use overlap fermions as valence quarks to calculate meson masses in a wide quark mass range
on the 2 + 1-flavor domain-wall fermion gauge configurations generated by the RBC and UKQCD
Collaborations. The well-defined quark masses in the overlap fermion formalism and the clear valence
quark mass dependence of meson masses observed from the calculation facilitate a direct derivation
of physical current quark masses through a global fit to the lattice data, which incorporates O(a2 )
correction, chiral extrapolation, and quark mass interpolation. Using the physical masses of Ds , Ds∗
and J/ψ as inputs, Sommer’s scale parameter r0 and the masses of charm quark and strange quark
in the MS scheme are determined to be r0 = 0.458(11)(8) fm, mMS
c (2 GeV) = 1.111(12)(22) GeV (or
MS
mMS
c (mc ) = 1.291(10)(18) GeV), and ms (2 GeV) = 0.103(6)(8) GeV, respectively. Furthermore,
we observe that the mass difference of the vector meson and the pseudoscalar meson with the same
valence quark contents is proportional to the reciprocal of the square root of the valence quark
masses. The hyperfine splitting of charmonium, MJ/ψ − Mηc , is determined to be 112(5)(3) MeV,
which is in good agreement with the experimental value. We also predict the decay constant of Ds
to be fDs = 256(5)(2) MeV. The masses of charmonium P -wave states χc0 , χc1 and hc are also in
good agreement with experiments.
PACS numbers: 11.15Ha, 12.38.Aw, 12.38.Gc, 13.30.Ce, 14.40.Pq, 14.40.Rt.
I.
INTRODUCTION
A large endeavor has been devoted by lattice QCD
to determine the quark masses which are of great importance for precision tests of the Standard Model of
particle physics [1–13]. In the lattice QCD formulation, quark masses are dimensionless bare parameters
and their renormalized values at a certain scale should
be determined through physical inputs. For the light u, d
quarks and the strange quark, their masses are usually set
by the physical pion and kaon masses as well as the decay constants fπ and fK , where the chiral extrapolation
is carried out through chiral perturbation theory [1–3].
For heavy quarks, the bare quark masses are first set in
the vicinity of the physical region and the physical point
can be interpolated or extrapolated through the quark
mass dependence observed empirically from the simulation. In the above procedures, non-perturbative quark
mass renormalization is usually required to match the
bare quark mass to the renormalized one at a fixed scale.
For the heavy quark, the HPQCD collaboration [5] proposed a promising scheme to obtain their masses from
current-current correlators of heavy quarkonium, which
is free of the quark mass renormalization [7].
In this work we propose a global-fit strategy to determine the strange and charm quark masses which incorporates simultaneously the O(a2 ) correction, the chiral
extrapolation, and the strange/charm quark interpolation. The lattice setup is a mixed action formalism where
we use the overlap fermions as valence quarks and carry
out the calculation on the domain-wall gauge configurations generated by the RBC and UKQCD Collaborations.
Both the domain-wall fermion (DWF) and the overlap
fermion are chiral fermions; as such, they do not have
O(a) errors for the valence quark masses, and the additive renormalization for them is also negligible (10−9 ) due
The melting of charmonium in a magnetic field from an effective AdS/QCD model
David Dudal1, 2, ∗ and Thomas G. Mertens2, †
1
KU Leuven Campus Kortrijk - KULAK, Department of Physics, Etienne Sabbelaan 53, 8500 Kortrijk, Belgium
2
Ghent University, Department of Physics and Astronomy, Krijgslaan 281-S9, 9000 Gent, Belgium
arXiv:1410.3297v1 [hep-th] 13 Oct 2014
We study the influence of a background magnetic field on the melting of the J/ψ vector meson
by introducing a Born-Infeld modification of the soft-wall model. Out of the three polarizations
of the massive vector meson, we find that the longitudinal one (parallel to the applied magnetic
field) melts only at an even higher temperature than the deconfinement temperature, whereas the
two transverse polarizations melt at a lower temperature than in the absence of a magnetic field.
We also conduct a preliminary investigation of the effect of the magnetic field on the heavy quark
diffusion coefficient, showing an increased diffusion constant for the longitudinal polarization with
respect to the transverse polarizations.
I.
INTRODUCTION
The quark-gluon plasma is a short-lived exotic state of QCD matter, in earth circumstances only present in controlled
laboratory environments, that is after a heavy ion collision (e.g. using Pb- or Au-ions). The ruling experiments are
RHIC and the LHC Alice facility. The state of deconfined quark-gluon matter is exotic, not only because it is hard to
create but its properties are not always as expected from a standard plasma [1]. Despite the ultrahigh temperature
at which the plasma is existing (∼ 1012 K), the plasma degrees of freedom are still strongly coupled, making a
perturbative analysis of the physics virtually impossible. This strong coupling nature of the plasma can be intuitively
understood from the observation that the relevant temperature —when reexpressed in more appropriate MeV units—
becomes of the order of the fundamental QCD scale ΛQCD , at which the QCD-interaction becomes strong.
A potential extra ingredient to further complicate matters was identified a few years ago [2–4]. It was discussed how
a noncentral heavy ion collision can produce very strong (short-lived) magnetic fields as well (∼ 1016 Tesla). Such
strong magnetic (B) fields can couple directly to the electrically charged quarks and, via the quarks, also indirectly to
the gluons. As this magnetic field is a collective effect, we can treat it as a classical external field and due to its size,
one might expect considerable effects onto the QCD dynamics. The recent review [5] contains a pleiad of new strange
QCD phenomena directly linked to the presence of a strong magnetic background. We point out that most studies
restrict to a constant (in time and position) magnetic field of the form B = Bez . There have been given (model
dependent) estimates of the magnetic field showing that during the initial stages after the collision during which the
plasma exists (∼ 1 − 10 fm), it is nearly constant [6], hence this approximation is a decent one that allows explicit
analyses, at least to some extent.
A particular riddle in magnetized QCD is the effect the magnetic field might have on the deconfinement transition.
An approach based on the linear sigma model coupled to the Polyakov loop [7] predicted an increasing Tc in terms of
B, a result supported by an independent study using the Polyakov-Nambu-Jona-Lasinio model [8–10], while earlier
a nonlinear sigma model analysis predicted a decrease [11]. Quenched lattice QCD studies on one hand seemed to
support a (slight) decrease in Tc [12] at first, but the situation got more or less settled when unquenched results
(full quark dynamics) became available [13]; a direct study of the Polyakov loop or (strange) quark susceptibility
displayed a decreasing critical temperature for the confinement-deconfinement transition. Let us also refer to [14, 15]
for two-color QCD studies.
By now, also some analytical approximations were worked out which were capable of explaining a decreasing Tc ,
see e.g. [16, 17]. It is perhaps interesting to point out here that, frequently, the discussion about the deconfinement
transition in a magnetic field is coupled to that of the chiral transition. Since quarks couple directly to the magnetic
field, one could expect an even stronger response of the chiral transition to the B-field. The predictions of the papers
[7–10, 12–15] ranged from a split or no split between the 2 transition temperatures, with the temperatures rising or
going down with B. The already mentioned lattice QCD study [13] in fact were most focused on disfavoring this rising
∗
†
david.dudal@kuleuven-kulak.be
thomas.mertens@ugent.be
arXiv:1410.3107v1 [cond-mat.str-el] 12 Oct 2014
Differences and analogies between quantum
chromodynamics and ferromagnets
C P Hofmann1
1
Facultad de Ciencias, Universidad de Colima, Bernal D´ıaz del Castillo 340, Colima C.P.
28045, Mexico
E-mail: christoph.peter.hofmann@gmail.com
Abstract. The low-energy physics of quantum chromodynamics (QCD) and ferromagnets is
dominated by Goldstone bosons. While the effective theory of QCD - chiral perturbation theory
- is well established in the particle physics community, the systematic studies of ferromagnetic
systems within the effective Lagrangian framework are not well-known. We analyze the lowtemperature properties of ferromagnets in one, two and three space dimensions up to three-loop
order in the effective expansion, i.e., beyond the accuracy of any previous results obtained
with conventional condensed matter methods. In particular, in the nonrelativistic domain, the
effective method perfectly works in one space dimension.
1. Motivation
The effective field theory of quantum chromodynamics (QCD), chiral perturbation theory, is
very-well established in particle physics. The method was originally devised for zero temperature
[1, 2, 3], but has been extended to finite temperature soon after [4, 5]. There are many excellent
outlines of the method available – the interested reader may want to consult Refs. [6, 7, 8, 9, 10].
In the present overview, we are interested in the description of relativistic and nonrelativistic
systems at nonzero temperature. In fact, the low-temperature properties of QCD have been
systematically analyzed in a series of papers a long time ago [4, 5, 11]. One important result
of these studies is the three-loop formula for the order parameter, i.e., the quark condensate,
which takes the following form [11],
h¯
q qi(T, mq )
= 1 − β0 T 2 − β1 T4 − β2 T6 lnT + O(T8 ),
h0|¯
q q|0i
(1)
where h0|¯
q q|0i is the quark condensate at zero temperature. Note that the boldfaced terms
are those contributions that result from the interaction among the Goldstone bosons, while the
leading temperature-dependent term corresponds to free Goldstone bosons.
The effective field theory method, however, is not restricted to the relativistic domain.
Indeed, the effective Lagrangian technique has been transferred to nonrelativistic systems in
Ref. [12]. In particular, the effective Lagrangian for the ferromagnet was established in that
reference. In analogy to the low-temperature expansion of the quark condensate and other
thermodynamic quantities, in this talk, we will be interested in the behavior of the (spontaneous)
magnetization and other observables of ferromagnets in one, two and three space dimensions –
detailed information can be found in the original papers [13, 14, 15, 16, 17, 18]. We will present
arXiv:1410.2907v1 [astro-ph.HE] 10 Oct 2014
Massive Black Hole Science with eLISA
Enrico Barausse1,2 , Jillian Bellovary3,4 , Emanuele Berti5 , Kelly
Holley-Bockelmann3,4 , Brian Farris6,7 , Bangalore Sathyaprakash8 ,
Alberto Sesana9
1
CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98bis Bd Arago, 75014 Paris, France
Sorbonne Universit´es, UPMC Univ Paris 06, UMR 7095, 98bis Bd Arago, 75014 Paris, France
3
Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
4
Department of Physics, Fisk University, Nashville, TN 37208, USA
5
Department of Physics and Astronomy, The University of Mississippi, University, MS 38677,
USA
6
Center for Cosmology and Particle Physics, Physics Department, New York University, New
York, NY 10003, USA
7
Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY
10027, USA
8
School of Physics and Astronomy, Cardiff University, 5, The Parade, Cardiff, CF24 3AA,
United Kingdom1
9
Max-Planck-Institut f¨
ur Gravitationsphysik, Albert Einstein Institut, D-14476, Golm,
Germany
2
Abstract. The evolving Laser Interferometer Space Antenna (eLISA) will revolutionize our
understanding of the formation and evolution of massive black holes (MBHs) along cosmic
history, by probing massive black hole binaries (MBHBs) in the 103 − 107 M range out to
redshift z & 10 . High signal-to-noise ratio detections of ∼ 10 − 100 MBHB coalescences per
year will allow accurate measurements of the parameters of individual MBHBs (such as their
masses, spins and luminosity distance), and a deep understanding of the underlying cosmic
MBH parent population. This wealth of unprecedented information can lead to breakthroughs
in many areas of physics, including astrophysics, cosmology and fundamental physics. We review
the current status of the field, recent progress and future challenges.
1. Introduction
The evolving Laser Interferometer Space Antenna (eLISA, [1]) is designed to be sensitive
to gravitational waves (GWs) at mHz frequencies. One of the strongest sources in this
frequency window are MBHBs merging throughout the Universe [2]. According to our current
understanding of structure formation in a ΛCDM Universe, MBHBs frequently form along cosmic
history following galaxy mergers. MBHs we see in today’s galaxies are expected to be the natural
end-product of a complex evolutionary path, in which black holes (BHs) seeded in proto-galaxies
at high redshift grow through cosmic history via a sequence of MBHB mergers and accretion
episodes [3, 4]. However, our current observational knowledge of the MBH population is limited
to a small fraction of these objects: either those that are active (see e.g. [5]), or those in our
neighborhood, where stellar- and gas-dynamical measurements are possible (see [6] for a review).
1
Currently on sabbatical leave at LIGO Laboratory, California Institute of Technology, MS 100-36, Pasadena,
CA 91125
Signatures of Kinematic Substructure in the Galactic Stellar Halo
Mariangela Lisanti,1 David N. Spergel,2 and Piero Madau3, 4
1
Department of Physics, Princeton University, Princeton, NJ 08544
Department of Astrophysical Science, Princeton University, Princeton, NJ 08544
3
Department of Astronomy & Astrophysics, University of California Santa Cruz, Santa Cruz, CA 95064
4
Center for Theoretical Astrophysics and Cosmology,
Institute for Computational Science, University of Zurich, CH-9057 Zurich, Switzerland
(Dated: October 10, 2014)
arXiv:1410.2243v1 [astro-ph.GA] 8 Oct 2014
2
Tidal debris from infalling satellites can leave observable structure in the phase-space distribution
of the Galactic halo. Such substructure can be manifest in the spatial and/or velocity distributions
of the stars in the halo. This paper focuses on a class of substructure that is purely kinematic in
nature, with no accompanying spatial features. To study its properties, we use a simulated stellar
halo created by dynamically populating the Via Lactea II high-resolution N -body simulation with
stars. A significant fraction of the stars in the inner halo of Via Lactea share a common speed
and metallicity, despite the fact that they are spatially diffuse. We argue that this kinematic substructure is a generic feature of tidal debris from older mergers and may explain the detection of
radial-velocity substructure in the inner halo made by the Sloan Extension for Galactic Understanding and Exploration (SEGUE). The GAIA satellite, which will provide the proper motions of an
unprecedented number of stars, should further characterize the kinematic substructure in the inner
halo. Our study of the Via Lactea simulation suggests that the stellar halo can be used to map the
speed distribution of the local dark-matter halo, which has important consequences for dark-matter
direct-detection experiments.
I.
INTRODUCTION
The process of galaxy formation alters the phase-space
distribution of the dark matter (DM) and stellar components of the Milky Way (MW) halo. The nature of
the residual phase-space structure in the halo depends
on the details of its formation history, and is sensitive
to whether the galaxy formed from smooth collapse [1]
or from the merger of many protogalactic fragments [2].
The ΛCDM paradigm currently provides the most wellmotivated picture of MW formation, including both the
dark and baryonic matter as basic ingredients. In the
ΛCDM framework, the MW halo forms from the hierarchical merging of smaller subhalos [3]. The subhalos
are tidally disrupted as they fall into the host, and dark
matter is torn off, along with stars that formed in the
dense cores of the subhalos.
Tidal remnants from a completely disrupted subhalo
eventually come into equilibrium with the host halo. An
incomplete merging event, however, leaves tidal debris
with phase-space structure distinguishable from that of
the smooth equilibrated halo. Dwarf galaxies are examples of infalling satellites that have not been completely
disrupted. These dwarfs orbit about the MW, leaving
tidal debris in their wake, especially near the turning
points of their orbits where the tidal forces are strongest.
After tidal stripping, the debris exhibits distinctive structure in both position and velocity. With time, the debris
comes into equilibrium with the host, and any distinctive
phase-space features are washed out.
The accretion events that build the MW stellar halo
leave their imprint on the phase-space distribution of
its constituent stars [4, 5]. This structure persists for
some time because stars exchange energy and momenta
on timescales that are much longer than the age of the
Galaxy [6]. As a result, structure in the stellar halo serves
as a fossil record of the MW’s formation history and kinematic or spatial features may be indicative of one or more
merger events.
The chemical composition of stars provides additional
information about their origin [7]. The metal content
is particularly indicative because iron is introduced into
the interstellar medium from supernova explosions, and
is thus related to the total integrated star formation. The
chemical properties of stars brought into the MW halo
depend on the mass of their subhalo host because a more
massive subhalo has had more time to form stars, and
also retains more metal. The stars that are deposited in
the MW by such mergers are typically more metal-rich
than those deposited earlier by smaller subhalos [8].
Evidence for stellar substructure has been accumulating with the advent of large-scale surveys, such as
the Sloan Digital Sky Survey (SDSS) [9], the Sloan
Extension for Galactic Understanding and Exploration
(SEGUE) [10], the Spaghetti survey [11], the Two Micron All Sky Survey [12], the Quasar Equatorial Survey
Team (QUEST) [13], and the Radial Velocity Experiment (RAVE) [14]. The Sagittarius dwarf [15] is one of
the most stunning examples of stellar substructure from
an on-going accretion event; the dwarf is in the midst
of a merger with the Milky Way and the tidal stream it
has left in its orbital wake has been mapped to amazing precision [16–21]. Many other examples of stellar
substructure have been documented [22–48] – e.g., the
Monoceros “Ring” [49–51], the Orphan Stream [52–54],
the Virgo Stellar Stream [55, 56], and tidal tails near the
Pal 5 [57, 58] and NGC 5466 [59, 60] globular clusters.
We find that it is useful to classify stellar substructure
Evidence for cosmic neutrino background form CMB circular polarization
Rohoollah Mohammadi
a
School of physics, Institute for research in fundamental sciences (IPM), Tehran, Iran.
Iran Science and Technology Museum (IRSTM), PO BOX: 11369-14611, Tehran, Iran.
arXiv:1312.2199v3 [astro-ph.CO] 7 Aug 2014
The primordial anisotropies of the cosmic microwave background are linearly polarized via
Compton-scattering. On the other hand, a primordial degree of circular polarization of the
Cosmic Microwave Background is not observationally excluded. In this work, we discuss the
generation of the circular polarization of CMB via their scattering on the cosmic neutrino
background since the epoch of recombination. We show that photon-neutrino interaction can
transform plane polarization into circular polarization through processes γ + ν → γ + ν and
the Stokes-V parameter of CMB has linear dependence on the wavelength and the cosmic
neutrino background perturbations of pressure and shear stress and also the maximum value
of C V is estimated in range of a few Nano-Kelvin square.
a
rmohammadi@ipm.ir
2
I.
INTRODUCTION
Modern cosmological observations of the Cosmic Microwave Background (CMB) radiation contain valuable information about our universe. The CMB photons have decoupled from matter
about 3 × 105 years after the Big-Bang (BB), so we are unable to probe the universe closer than
300 000 years to the BB by using CMB. Cosmological information encoded in the CMB radiation
concerns not only temperature fluctuations and the spectrum of anisotropy pattern, but also the
intensity and spectrum of linear and circular polarizations. From a result of the anisotropic Compton scattering around the epoch of recombination, it is generally expected that some relevant linear
polarizations (about 10%) of CMB radiation should be present [1–3], and polarization fluctuations
are smaller than the temperature fluctuations [5]. Currently, there are several ongoing experiments
[6–11, 40] attempting to measure CMB polarizations. Theoretical studies of CMB polarizations
were carried out in Refs. [1–4], and numerical calculations [13, 14] have confirmed that about 10%
of the CMB radiation is linearly polarized, via the Compton and Thompson scattering of unpolarized photons at the last scattering surface (the redshift z ∼ 103 ). Polarized light is conventionally
described in terms of the Stokes parameters, a linearly polarized radiation is described by nonzero values for the Stokes parameters Q and/or U and the possibility of the generation of circular
polarization can be determined by the Stokes parameter V [15]. On the basis of the mechanism
discussed in [1], the linear polarization of the CMB in the presence of a large-scale magnetic field
B can be converted to the circular polarization under the formalism of the generalized Faraday rotation (FR) [19, 20] known as the Faraday conversion (FC). The evolution of the Stokes parameter
V given by this mechanism is obtained as
d
V˙ = 2U (∆φF C ),
dt
(1)
where ∆φF C ∝ B 2 is the Faraday conversion phase shift [20]. There are several papers which have
attempted to discuss the probability of the generation of circular polarization of CMB photons.
Giovannini has shown that if the CMB photons are scattered via electrons in the presence of a magnetic field, a non-vanishing V mode can be produced [22, 23]. Furthermore, Cooray, Melchiorri and
Silk have discussed that the CMB radiation observed today is not exactly the same as the field last
scattered [20], Bavarsad et al have shown that CMB polarization acquires a small degree of circular
polarization when a background magnetic field is considered or the quantum electrodynamic sector
of standard model is extended by Lorentz non-invariant operators as well as non-commutativity
[21], Motie and Xue have discussed that the circular polarizations of radiation fields can be generated from the effective Euler-Heisenberg Lagrangian [24] and the transform plane polarization
arXiv:1410.3432v1 [hep-ph] 13 Oct 2014
RM3-TH/14-15
MPP-2014-373
Two-loop QCD corrections to the MSSM Higgs masses
beyond the effective-potential approximation
G. Degrassia , S. Di Vitab and P. Slavichc,d
a
Dipartimento di Matematica e Fisica, Universit`a di Roma Tre and INFN, Sezione di Roma Tre
Via della Vasca Navale 84, I-00146 Rome, Italy
b
c
Max-Planck-Institut f¨
ur Physik, F¨ohringer Ring 6, D-80805 Munich, Germany
LPTHE, UPMC Univ. Paris 06, Sorbonne Universit´es, 4 Place Jussieu, F-75252 Paris, France
d
LPTHE, CNRS, 4 Place Jussieu, F-75252 Paris, France
Abstract
We compute the two-loop QCD corrections to the neutral Higgs-boson masses in the MSSM,
including the effect of non-vanishing external momenta in the self-energies. We obtain corrections
of O(αt αs ) and O(ααs ), i.e., all two-loop corrections that involve the strong gauge coupling when
the only non-vanishing Yukawa coupling is the top one. We adopt either the DR renormalization
scheme or a mixed OS–DR scheme where the top/stop parameters are renormalized on-shell. We
compare our results with those of earlier calculations, pointing out an inconsistency in a recent
result obtained in the mixed OS–DR scheme. The numerical impact of the new corrections on the
prediction for the lightest-scalar mass is moderate, but already comparable to the accuracy of the
Higgs-mass measurement at the LHC.
e-mail:
degrassi@fis.uniroma3.it
divita@mpp.mpg.de
slavich@lpthe.jussieu.fr
Electrical Conductivity of Dense Quark Matter with
Fluctuations and Magnetic Field Included
B.O. Kerbikov
∗1,2
and M.A. Andreichikov
†1,2
arXiv:1410.3413v1 [hep-ph] 13 Oct 2014
1
Institute of Theoretical and Experimental Physics, Bolshaya
Cheremushhkinskaya 25, 117218, Moscow, Russia
2
Moscow Institute of Physics and Technology, Institutsky Pereulok 9, 141700,
Dolgoprudny, Moscow Region, Russia
October 14, 2014
Abstract
We investigate the electrical conductivity(EC) of dense quark matter in the vicinity of the phase transition line. We show that: (i) At high density the Drude EC
does not depend on the magnetic field up to eB ∼ 1019 G. (ii) In the precritical
region the fluctuation EC (paraconductivity) dominates over the Drude one.
1
Introduction
QCD under extreme conditions has been the subject of the intense study for the last
decade. A large body of experimental data on heavy ion collisions obtained at RHIC and
LHC has lead to a revolutionary change in our view on the properties of QCD matter at
finite temperature and density. These properties depend on the location of the system
in the QCD phase diagram, i.e., on the values of the temperature and the chemical
potential. Roughly speaking, information obtained at RHIC and LHC corresponds to
the high temperature and low density region. Our focus in the present paper is on
the opposite regime of high density and moderate temperature. Such conditions may be
realized in neutron stars and in future experiments at NICA and FAIR. On the theoretical
side we understand much better what happens to quark-gluon matter at high T and zero,
or small µ, than in the reverse situation. To a great extent this is due to the fact that
zero µ and high T region is accessible to Monte-Carlo simulations. According to the
∗
†
borisk@itep.ru
andreichicov@mail.ru
1
Tau Portal Dark Matter models at the LHC
Zhao-Huan Yu1 , Xiao-Jun Bi1 , Qi-Shu Yan2,3 , and Peng-Fei Yin1
1
arXiv:1410.3347v1 [hep-ph] 13 Oct 2014
Key Laboratory of Particle Astrophysics, Institute of High Energy Physics,
Chinese Academy of Sciences, Beijing 100049, China
2
School of Physics, University of Chinese Academy of Sciences, Beijing 100049, China and
3
Center for High Energy Physics, Peking University, Beijing 100871, China
Motivated by the Galactic Center gamma-ray excess in the Fermi-LAT data, we study the signatures of a class of tau portal dark matter (DM) models where DM particles preferentially couple to
tau leptons at the LHC. We consider the constraints from the DM direct detection and investigate
the sensitivity of the LHC to di-tau plus missing energy signatures. We find that the LHC with a
high luminosity of 3000 fb−1 can test the tau portal DM models with fermionic mediators in the
mass range of 120 ∼ 450 GeV.
PACS numbers: 95.35.+d,12.60.-i
I.
INTRODUCTION
Various astrophysical and cosmological observations
have confirmed that the main component of the matter
in the Universe is non-baryonic dark matter. There is a
class of attractive DM candidates called weakly interacting massive particles with masses of O(1) − O(103 ) GeV.
Their annihilations in regions with high DM densities
can effectively generate energetic cosmic rays, such as
gamma-rays, neutrinos, and antimatter particles, which
could be captured by DM indirect detection experiments.
Compared with charged particles, gamma-rays are less
affected by the interstellar matter and the Galactic magnetic field during their propagation. Thus their energy
spectra and directions as well as their origins can be well
determined. Therefore, gamma-rays could be a very good
probe to reveal the microscopic properties of DM particles in the Galaxy.
Recently, several groups reported an extended gammaray excess with a high significance peaking at a few GeV
in the Fermi Large Area Telescope data [1–11]. This excess emission is found in the Galactic Center (GC) and
even a larger region up to 10◦ from the GC after subtracting well-known astrophysical backgrounds. The spatial distribution of the excess is similar to the square of
the Navarro-Frenk-White DM distribution [12]. A study
showed that such an excess is not contributed by emissions from the Fermi bubbles [8]. However, it might arise
from other astrophysical sources, such as a population of
millisecond pulsars [13, 14] or high energy cosmic rays
from the explosion in the GC [15, 16]. Nevertheless,
whether these astrophysical sources can simultaneously
interpret the total flux, energy spectrum, and spatial distribution of the excess is still debatable [14, 17, 18].
An attractive and economic explanation for the
gamma-ray excess is DM annihilations, if only the DM
distribution is a steep Navarro-Frenk-White profile ∼ r−γ
with an inner slope γ ∼ 1.2. DM particles may directly annihilate into b quarks, light quarks, charged
leptons [1, 2, 4, 8], or some new light particles [19–21],
which further produce photons from their cascade decays
and/or final state radiations. For instance, the gammaray excess can be interpreted by a model with DM particles annihilating into b¯b with a mass of 30 − 40 GeV
and a cross section of ∼ 10−26 cm−1 s−1 [7, 8], which can
naturally yield the correct DM relic density.
If DM particles dominantly couple to b quarks at
the tree level, they would generate nuclear recoil signatures via loop effects for DM direct detection experiments, which are very sensitive to O(10) GeV DM particles [22, 23]. Future underground experiments, such as
XENON and LUX, will test these scenarios. DM annihilations into b quarks in the Galaxy will also produce extra
antiprotons. Considering the PAMELA antiproton measurement with null excess [24], some works have found
stringent constraints on such DM models accounting for
the gamma-ray excess [25, 26]. Nonetheless, it is necessary to point out that these constraints are subject to
unavoidable astrophysical uncertainties from cosmic-ray
propagation and solar modulation models.
As well known, collider searches for dark matter are
complimentary to the direct and indirect detection experiments. At high energy colliders, DM particle productions can yield events with a significant large missing
/ T ). In order to explain the gammatransverse energy (E
ray excess, models with an appropriate mediator are favored. It is interesting to notice that the required DM
particle mass and annihilation cross section indicate that
the mediator connecting DM and SM particles should be
around O(102 ) GeV or so, which seems within the searching capability of the LHC. Thus it is hopeful to observe
direct productions of the mediators at the LHC. For recent works on this topic, interested readers can refer the
papers [22, 23, 27–30].
In this work, we focus on a class of simplified tau portal
DM models where DM particles preferentially couples to
tau leptons. The ∼ O(1) TeV leptophilic DM particles
have been extensively studied to interpret the anomalous
high energy cosmic-ray positrons and electrons. Some recent works have investigated the collider phenomenology
of general leptophilic DM models with masses of O(102 )
GeV [31–33]. For a pure DM annihilation channel to
τ + τ − , the gamma-ray excess can be explained by the
The effect of multi-channel pion-pion scattering in decays of the
Υ-family mesons
Yu.S. Surovtsev(1)† , P. Bydˇzovsk´
y(2), T. Gutsche(3) , R. Kami´
nski(4) , V.E. Lyubovitskij(3,5,6) , and M. Nagy(7)
(1) Bogoliubov Laboratory of Theoretical Physics,
JINR,141 980 Dubna, Russia
arXiv:1410.3300v1 [hep-ph] 13 Oct 2014
(2) Nuclear Physics Institute of the AS CR,
ˇ z, Czech Republic
25068 Reˇ
(3) Institut f¨
ur Theoretische Physik, Universit¨
at T¨
ubingen,
Kepler Center for Astro and Particle Physics,
Auf der Morgenstelle 14, D–72076 T¨
ubingen, Germany
(4) Institute of Nuclear Physics of the PAN,
Cracow 31342, Poland
(5) Department of Physics,
Tomsk State University, 634050 Tomsk, Russia
(6) Mathematical Physics Department,
Tomsk Polytechnic University,
Lenin ave.30, 634050 Tomsk, Russia
(7) Institute of Physics, SAS,
Bratislava 84511, Slovak Republic
(Dated: October 14, 2014)
The effect of isoscalar S-wave multi-channel pion-pion scattering (ππ → ππ, KK, ηη) is considered
in the analysis of data on decays of the Υ-meson family – Υ(2S) → Υ(1S)ππ, Υ(3S) → Υ(1S)ππ and
Υ(3S) → Υ(2S)ππ. The analysis, which aims at studying the scalar mesons, is performed jointly
considering the multi-channel pion-pion scattering, which is described in our model-independent
approach based on analyticity and unitarity and using an uniformizing variable method, and the
charmonium decay processes J/ψ → φ(ππ, KK), ψ(2S) → J/ψ(ππ). Results of the analysis confirm
all our earlier conclusions on the scalar mesons. It is also shown that in the final states of the Υmeson family decays (except for the ππ scattering) the contribution of the coupled processes, e.g.,
KK → ππ, is important even if these processes are energetically forbidden. This is in accordance
with our previous conclusions on the wide resonances: If a wide resonance cannot decay into a
channel which opens above its mass but the resonance is strongly connected with this channel (e.g.
the f0 (500) and the KK channel), one should consider this resonance as a multi-channel state with
allowing for the indicated channel taking into account the Riemann-surface sheets related to the
threshold branch-point of this channel and performing the combined analysis of the considered and
coupled channels.
PACS numbers: 11.55.Bq,11.80.Gw,12.39.Mk,14.40.Cs
Keywords: coupled–channel formalism, meson–meson scattering, meson decays, scalar and pseudoscalar
mesons
I.
INTRODUCTION
In the analysis of data on decays of the Υ-meson family –Υ(2S) → Υ(1S)ππ, Υ(3S) → Υ(1S)ππ and Υ(3S) →
Υ(2S)ππ – the contribution of multi-channel ππ scattering in the final-state interactions is considered. The analysis,
which aims at studying the scalar mesons, is performed jointly considering the isoscalar S-wave processes ππ →
ππ, KK, ηη, which are described in our model-independent approach based on analyticity and unitarity and using an
uniformization procedure, and the charmonium decay processes J/ψ → φ(ππ, KK), ψ(2S) → J/ψ(ππ).
Importance of studying properties of scalar mesons is related to the obvious fact that a comprehension of these states
is necessary in principle for the most profound topics concerning the QCD vacuum, because these sectors affect each
other especially strongly due to possible ”direct” transitions between them. However the problem of interpretation of
Quarkonia suppression in PbPb collisions at
√
sNN =
2.76 TeV
Vineet Kumar1, 2 and Prashant Shukla1, 2, ∗
1
Nuclear Physics Division, Bhabha Atomic Research Center, Mumbai, India
arXiv:1410.3299v1 [hep-ph] 13 Oct 2014
2
Homi Bhabha National Institute, Anushakti Nagar, Mumbai, India
(Dated: October 14, 2014)
Abstract
We estimate the modification of quarkonia yields due to different processes in the medium produced in PbPb collisions at LHC energy. The quarkonia and heavy flavour cross sections calculated
upto Next to Leading Order (NLO) are used in the study and shadowing corrections are obtained
by EPS09 parametrization. A kinetic model is employed which incorporates quarkonia suppression
inside QGP, suppression due to hadronic comovers and regeneration from charm pairs. Quarkonia
dissociation cross section due to gluon collisions has been considered and the regeneration rate has
been obtained using the principle of detailed balance. The modification in quarkonia yields due
to collisions with hadronic comovers has been estimated assuming it to be caused by pions. The
manifestations of these effects in different kinematic regions in the nuclear modification factors for
√
both J/ψ and Υ has been demonstrated for PbPb collisions at sN N = 2.76 TeV in comparison
with the measurements. Both the suppression and regeneration due to deconfined medium strongly
affect low and intermediate pT range. The large observed suppression of J/ψ at pT above 10 GeV/c
exceeds the estimates of suppression by gluon dissociation.
PACS numbers: 12.38.Mh, 24.85.+p, 25.75.-q
Keywords: quark-gluon plasma, quarkonia, suppression, regeneration
∗
pshukla@barc.gov.in
1
Nuclear Physics B
Proceedings
Supplements
Nuclear Physics B Proceedings Supplements 00 (2014) 1–6
The KTY formalism and nonadiabatic contributions to the neutrino oscillation
probability
arXiv:1410.3279v1 [hep-ph] 13 Oct 2014
Osamu Yasuda
Department of Physics, Tokyo Metropolitan University, Minami-Osawa, Hachioji, Tokyo 192-0397, Japan
Abstract
It is shown how to obtain the analytical expression for the effective mixing angle in matter using the formalism
which was developed by Kimura, Takamura and Yokomakura. If the baseline of the neutrino path is long enough so
that averaging over rapid oscillations is a good approximation, then with the help of Landau’s method, the nonadiabatic
contribution to the oscillation probability can be expressed analytically by this formalism. We give two examples in
which the present method becomes useful.
Keywords: neutrino oscillation, nonadiabatic transition, the KTY formalism
1. Introduction
Neutrino oscillation is a quantum mechanical interference effect which sometimes has complex behaviors,
particularly in matter. To discuss the behaviors of neutrino oscillation intuitively, it is important to have analytical formulae for the oscillation probability. Unfortunately, an analytical formula in the three flavor mixing
scheme in matter is quite complicated. In 2002 Kimura,
Takamura and Yokomakura (KTY) discovered a compact formula [1, 2] for the neutrino oscillation probability in matter with constant density. Subsequently the
KTY framework was generalized to more general cases.
Ref. [3] discussed the four neutrino mixing scheme in
matter with constant density. Ref. [4] discussed the case
with unitarity violation. Ref. [5] discussed two cases
of neutrino oscillation in the adiabatic approximation,
the one with non-standard interactions where the matter
potential has non-diagonal elements in the flavor basis,
or the other with large neutrino magnetic moments in a
magnetic field.
In general, however, adiabatic approximation may
not be good, and in this talk I discuss nonadiabatic
contributions to the oscillation probability. When there
are more than two neutrino mass eigenstates, there can
be more than one level crossing. It is believed 1 that
the nonadiabatic contributions to the transition phenomena in a problem with three or more eigenstates can be
treated approximately well by applying the method for
two state problems [8, 9] at each level crossing, if the
the two resonances are sufficiently far apart. Throughout this talk I discuss the case in which the baseline of
the neutrino path is long enough so that averaging over
rapid oscillations is a good approximation, as in the case
of the solar neutrino deficit phenomena.
2. The oscillation probability
2.1. The oscillation probability in the adiabatic approximation
The equation of motion for neutrinos propagating in
matter with general potential is given by
i
i
dΨ h
= UE0 U −1 + A(t) Ψ,
dt
(1)
1 See, e.g., Ref. [6] and references therein. See also Ref. [7] for a
discussion on the condition to justify such a treatment.
Scaling ansatz with texture zeros in linear seesaw
arXiv:1410.3276v1 [hep-ph] 13 Oct 2014
Mainak Chakrabortya∗, H. Zeen Devib†, Ambar Ghosala‡
a) Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India
b) University of Technology and Management, Shillong, Meghalaya 793003
October 14, 2014
Abstract
We investigate scaling ansatz with texture zeros within the framework of linear seesaw mechanism. In this variant of seesaw mechanism a simplified expression of effective neutrino mass
matrix mν containing two Dirac type matrices (mD and mDS ) and one Majorana type matrix
(mRS ) is obtained by virtue of neglecting the global U (1)L symmetry breaking term in the
mass term of the Lagrangian. Along with the charged lepton mass matrix, the matrix mRS
too is chosen in a diagonal basis whereas a scaling relation is incorporated in mD and mDS
with different scale factors. Our goal in this work is to achieve a completely phenomenologically
acceptable mν generated with combinations of mD and mDS containing least number of independent parameters or maximum number of zeros. At the end of the numerical analysis it is
found that number of zeros in any of the constituent Dirac type matrices (mD and mDS ) of mν
can not be greater than six in order to meet the phenomenological requirements. The hierarchy
P
obtained here is normal and also the values of the two parameters sum mass ( mi ) and |mνee |
are below the present experimental lower limit.
∗
mainak.chakraborty@saha.ac.in
zdevi@utm.ac.in
‡
ambar.ghosal@saha.ac.in
†
1
Lessons from LHC elastic and diffractive data
A.D. Martin, V.A. Khoze and M.G. Ryskin
arXiv:1410.3261v1 [hep-ph] 13 Oct 2014
Institute for Particle Physics Phenomenology, Durham University, Durham, DH1 3LE
Abstract. In the light of LHC data, we discuss the global description of all high energy elastic and diffractive data, using a
one-pomeron model, but including multi-pomeron interactions. The LHC data indicate the need of a kt (s) behaviour, where kt
is the gluon transverse momentum along the partonic ladder structure which describes the pomeron. We also discuss tensions
in the data, as well as the t dependence of the slope of dσel /dt in the small t domain.
Keywords: LHC, elastic scattering, t-slope, diffractive dissociation, perturbative QCD
PACS: 13.85.Dz, 13.85.Lg, 11.80.Gw
DESCRIPTION OF ‘SOFT’ DATA BEFORE LHC
The KMR [1] approach to describe high-energy elastic and diffractive pp data uses the framework of Regge pomeron
theory, which includes non-enhanced eikonal-like multi-pomeron interactions together with the Good-Walker formalism [2] for diffractive eigenstates to describe elastic scattering and low-mass proton dissociation. High-mass dissociation is described by including multi-pomeron vertices which account for the rescattering of intermediate partons. The
procedure is sketched below:
FIGURE 1. The first equation sketches the multi-channel eikonal expression of the amplitude for the scattering of diffractive
eigenstates i, k – states that are the linear combinations of |pi, |p∗ i, ... which undergo elastic-type scattering. In this way we can
describe elastic scattering and low-mass dissociation. Next we show the multi-pomeron diagrams, that involve the coupling gm
n
of m to n pomerons, which allow for high-mass dissociation – the simplest being the triple-pomeron diagram describing proton
dissociation into the high-mass M system. All the ‘t-channel lines’ represent pomeron exchange, which in pQCD have a ladder-type
structure – we speak of the ‘hard’ or ‘BFKL’ pomeron.
Contrary to conventional Regge theory, where it was assumed that all transverse momenta, kt , are limited, we try
to match the perturbative QCD and Regge Field Theory (RFT) approaches. We start with the BFKL hard pomeron,
where the parton kt may increase or decrease at each step of the log(1/x) evolution (along the ‘ladder’). However,
stronger absorption of the low kt partons, described by multi-pomeron vertices, leads to a growth of hkt i with energy.
This justifies the pQCD approach, and. moreover, is consistent with the increase of the infrared cutoff with energy,
kt min ∝ s0.12 , which is needed to describe the spectra of secondaries by the Monte Carlo generators [3, 4]
The growth of kt min with energy is generated by the evolution of the hard pomeron. It is the appearance of this
dynamical cutoff which allows us to extrapolate the predictions of pQCD from the large kt region to the soft domain.
In more detail, at LO, the parton density is described by the BFKL equation
∂ f (y, kt )
= αs
∂y
Z
d 2 kt0 K(kt , kt0 ) f (y, kt0 )
(1)
arXiv:1410.3252v1 [hep-ph] 13 Oct 2014
A development of an accelerator board dedicated for
multi-precision arithmetic operations and its
application to Feynman loop integrals
S Motoki1 , H Daisaka2 , N Nakasato3 , T Ishikawa1 , F Yuasa1 ,
T Fukushige4 , A Kawai4 , J Makino5
1
High Energy Accelerator Research Organization (KEK), 1–1, Oho, Tsukuba, Ibaraki,
305–0801, Japan
2
Hitotsubashi University, 2–1, Naka, Kunitachi, Tokyo, 186–0801, Japan
3
University of Aizu, Aizu-wakamatsu, Fukushima, 965–8580, Japan
4
K&F Computing Research Co., 1–21–6–407, Kojimacho, Chofu, Tokyo, 182–0026, Japan
5
RIKEN Advanced Institute for Computational Science, 7–1–26, Minatojima-minami-machi,
Chuo-ku, Kobe, Hyogo, 650–0047, Japan
E-mail: smotoki@post.kek.jp
Abstract. Higher order corrections in perturbative quantum field theory are required for
precise theoretical analysis to investigate new physics beyond the Standard Model. This
indicates that we need to evaluate Feynman loop diagram with multi-loop integral which may
require multi-precision calculation. We developed a dedicated accelerator system for multiprecision calculation (GRAPE9-MPX). We present performance results of our system for the
case of Feynman two-loop box and three-loop selfenergy diagrams with multi-precision.
1. Introduction
With the discovery of Higgs particle in CERN Large Hadron Collider, precision measurements
are expected in future International Linear Collider to explore new physics beyond the Standard
Model. In tandem with experiments, an accurate theoretical prediction is required. To meet
such a demand, higher order correction in perturbative quantum field theory becomes more and
more important, and the method to evaluate multi-loop integrals precisely should be provided.
We have been developing DCM (Direct Computation Method) for loop integrals [1]. This
is a fully numerical method of the combination of multi-dimensional integration and the
extrapolation technique. It is known that the accurate numerical evaluation of the integral
is a hard problem due to its divergent nature. Yuasa et al. [2] reported that the numerical
evaluation is numerically unstable with double-precision operations. A solution to this difficulty
is to compute the integral in multi-precision arithmetic, that is, it needs more bits for mantissa
than double-precision. In addition, we have a case that needs more bits for exponent. With
Double Exponential Formulas for numerical integration (DE) [3], we can estimate that 15-bit
wise exponent is required to reduce a relative error smaller than a reference value, although the
exponent of double-precision is only 11-bit wise.
There are several ways to accomplish multi-precision arithmetic. One way is to use the specific
softwares, for examples, GMP [4], MPFR [5], ARPREC [6], MPFUN90 [6], DD/QD [6], and quadmath on
SUSY explanation of the Fermi Galactic Center Excess
and its test at LHC Run-II
Junjie Cao1,2 , Liangliang Shang1,3 , Peiwen Wu3 , Jin Min Yang3 , Yang Zhang3
1
Department of Physics, Henan Normal University, Xinxiang 453007, China
Center for High Energy Physics, Peking University, Beijing 100871, China
State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Academia Sinica, Beijing 100190, China
(Dated: October 14, 2014)
2
arXiv:1410.3239v1 [hep-ph] 13 Oct 2014
3
We explore the explanation of the Fermi Galactic Center Excess (GCE) in the Next-to-Minimal
Supersymmetric Standard Model. We systematically impose various experimental constraints and
perform a fit to the updated Higgs data. For each surviving sample we further generate its gammaray spectrum from dark matter (DM) annihilation and compare it directly with the Fermi data. We
find that the GCE can be explained by the annihilation χχ → a∗ → b¯b only when the CP-odd scalar
satisfies ma ≃ 2mχ , and in order to obtain the measured DM relic density, a sizable Z-mediated
contribution to DM annihilation must intervene in the early universe. As a result, the higgsino mass
µ is upper bounded by about 350 GeV. Detailed Monte Carlo simulations on the 3ℓ + ETmiss signal
from neutralino/chargino associated production at 14-TeV LHC indicate that the explanation can
be mostly (completely) excluded at 95% C.L. with an integrated luminosity of 100(200) fb−1 .
I.
INTRODUCTION
As a building block of the universe, Dark Matter (DM)
is a focus of current particle physics. The existence of a
Weakly Interacting Massive Particle (WIMP) as a DM
candidate has been indicated by some direct detection
experiments like DAMA/LIBRA [1] and CDMS [2], although these experimental results are not consistent with
each other very well and not supported by other experiments such as Xenon [3] and LUX [4]. On the other
hand, indirect DM searches, which look for the products
of DM annihilation or decay in the Galactic halo/center
and nearby dwarf galaxies or inside the sun, also reported
some anomalies. Recent data analyses of Fermi Gamma
Ray Space Telescope have shown an excess around 1 ∼ 4
GeV in the energy spectrum of secondary photons coming from the Galactic Center [5, 6]. It has been pointed
out that this gamma-ray excess can be well explained by
a ∼ 35 GeV DM annihilating 100% into b¯b with a thermal
averaged cross section of about 2 × 10−26 cm3 /s, which is
remarkably close to the value required by the measured
thermal relic density Ωh2 [5, 6].
So far several works have been devoted to interpret
such a Galactic Center Excess (GCE) in supersymmetry (SUSY) [7–10]. It was found that, after considering
the constraints from the relic density, the most promising
DM annihilation channel is χχ → a∗ → b¯b, where a is a
CP-odd Higgs boson with mass below about 100 GeV. In
the Minimal Supersymmetric Standard Model (MSSM),
due to the mass correlation between the pseudoscalar
and the charged/heavy CP-even scalar, the pseudoscalar
is generally heavier than about 300 GeV and thus cannot give an explanation for the GCE. In the Next-toMinimal Supersymmetric Standard Model (NMSSM), an
extra singlet superfield Sˆ is introduced and consequently
it predicts three CP-even Higgs bosons h1∼3 , two CPodd Higgs bosons a1,2 and five neutralinos χ
˜01∼5 (here
an ascending mass order is assumed for the same type
of particles, so χ
˜01 acts as DM, which is denoted by χ
hereafter) [11]. Since the CP-odd Higgs boson a1 may be
singlet-like and rather light, light DM pair can annihilate
mainly through the s−channel mediation of a1 in both
the early universe and today, and thus provide a possible
explanation for the GCE. In fact, as pointed out in [8],
in NMSSM a bino-like DM can explain both the GCE
and the measured Ωh2 through an off-shell a1 , while a
singlino-like DM requires a tuned resonance 2mχ ≃ ma1
to achieve the same goal.
We note that previous analyses usually assumed a wide
range of today’s DM annihilation rate hσvi|v→0 = (0.5 ∼
4.0) × 10−26 cm3 /s, which allows the height of the photon spectrum to vary greatly, i.e. E 2 dN/dE = (1.0 ∼
7.0) × 10−6 GeV/(cm2 · s · sr) for mχ ≃ 35 GeV and
E = 2 GeV (see Fig.1 below). Consequently, the parameter regions favored by GCE are easy to coincide
with those favored by the measured Ωh2 . Moreover,
previous analyses usually missed some experimental constraints pertinent to the GCE explanation, such as the
LEP search for light Higgs bosons and recently updated
LHC Higgs data. So it is necessary to give a comprehensive study and further examine its implication at the
LHC Run-II.
In this work we scan the NMSSM parameter space by
considering various experimental constraints. Then for
each surviving sample, we generate the photon spectrum
so that we can compare it directly with the Fermi data
presented in [6] (we define an appropriate χ2γ for such
a comparison). Due to these improvements, we obtain
different observations from those in [8]. For example, we
find that a singlino-like DM instead of a bino-like DM is
easier to explain both the GCE and the measured Ωh2 .
More importantly, we observe that the annihilation process χχ → a∗1 → b¯b can not be alone responsible for both
the GCE and the measured Ωh2 , and in order to get the
correct Ωh2 , a sizable s-channel Z contribution to the DM
annihilation in the early universe is usually necessary. As
a result, the higgsino mass µ is upper bounded by about
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–7
DESY-14-183
arXiv:1410.3237v1 [hep-ph] 13 Oct 2014
GoSam 2.0: Automated one loop calculations within and beyond the Standard
Model
Nicolas Greinera,b
a Max-Planck-Institut
b DESY
f¨ur Physik, F¨ohringer Ring 6, 80805 M¨unchen, Germany
Theory Group, Notkestr. 85, D-22607 Hamburg, Germany
Abstract
We present GoSam 2.0, a fully automated framework for the generation and evaluation of one loop amplitudes in
multi leg processes. The new version offers numerous improvements both on generational aspects as well as on the
reduction side. This leads to a faster and more stable code for calculations within and beyond the Standard Model.
Furthermore it contains the extended version of the standardized interface to Monte Carlo programs which allows
for an easy combination with other existing tools. We briefly describe the conceptual innovations and present some
phenomenological results.
Keywords: NLO, Automation, QCD, BSM
1. Introduction
have been obtained with GoSam 2.0.
Two of the main challenges for the upcoming run
2 of the LHC will be a more precise determination of
the Higgs [1, 2] properties and its couplings to bosons
and fermions as well as the continued searches for new
physics.
Both cases require a precise prediction for both signal
and background processes. This particularly includes
the calculation of next-to-leading order corrections in
QCD. One of the main bottlenecks of such a computation is the calculation of the virtual one loop amplitude.
The complexity and the need for having reliable tools
for a large variety of different processes has lead to the
development of multi-purpose automated tools. An example of such a tool is the GoSam package [3] that focuses on the efficient generation and numerical evaluation of one loop amplitudes. The continious refinement
and extension of the existing package has lead to the
publication of the version 2.0 [4]. In this talk we will
describe the improvements and new features contained
in the the new version and present selected results that
2. New features in GoSam 2.0
2.1. Improvements in code generation
2.1.1. Code optimisation with FORM
GoSam generates an algebraic expression for each
amplitude which is written in a Fortran90 file. It is obvious that the time needed to evaluate a single phase
space point is highly dependent on how optimised the
expression is written. In the first version the generation
of an optimised expression has been done with the help
of haggies [5]. In the new version we make use of new
features provided by FORM version 4.x [6]. The new
features result in a more compact code and a gain in
speed of up to an order of magnitude.
2.1.2. Summing of diagrams with common subdiagrams
In order to improve the efficiency and the evaluation time, GoSam 2.0 is able to automatically sum algebraically diagrams that exhibit a similar structure to
arXiv:1410.3225v1 [hep-ph] 13 Oct 2014
Impact parameter space and transverse distortion
Harleen DAHIYA∗†
Department of Physics, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar, 144011,
India
E-mail: dahiyah@nitj.ac.in
Narinder KUMAR
Department of Physics, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar, 144011,
India
We investigate the GPDs in impact parameter space using the explicit light front wave functions
(LFWFs) for the two-particle Fock state of the electron in QED. The Fourier transform (FT) of
the GPDs gives the distribution of quarks in the transverse plane for zero longitudinal momentum
transfer (ζ = 0). We study the relationship of the spin flip GPD with the distortion of unpolarized
quark distribution in the transverse plane when the target nucleon is transversely polarized and
also determine the sign of distortion from the sign of anomalous magnetic moment.
XXII. International Workshop on Deep-Inelastic Scattering and Related Subjects,
28 April - 2 May 2014
Warsaw, Poland
∗ Speaker.
† Authors would like to thank S.J. Brodsky for helpful discussions and Department of Science and Technology,
Government of India for financial support.
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
http://pos.sissa.it/
Impact parameter space and transverse distortion
Harleen DAHIYA
1. Introduction
Deep virtual compton scattering (DVCS) [1, 2, 3, 4] is the main process to probe the internal
structure of hadrons. Recently, the Generalized Parton Distributions (GPDs) [5, 6, 7, 8, 9] have
attracted a considerable amount of interest towards this. GPDs allow us to access partonic configurations not only with a given longitudinal momentum fraction but also at a specific (transverse)
location inside the hadron. GPDs can be related to the angular momentum carried by quarks in the
nucleon and the distribution of quarks can be described in the longitudinal direction as well as in
the impact parameter space [10, 11, 12, 13]. When integrated over x the GPDs reduce to the form
factors which are the non-forward matrix element of the current operator and they describe how
the forwards matrix element (charge) is distributed in position space. On the other hand, Fourier
transform (FT) of GPDs w.r.t. transverse momentum transfer gives the distribution of partons in
transverse position space [11, 12]. Therefore, their should be some connection between transverse
position of partons and FT of GPDs w.r.t. transverse momentum transfer.
With the help of impact parameter dependent parton distribution function (ipdpdf) one can
obtain the transverse position of partons in the transverse plane. However, it is not possible to
measure the longitudinal position of partons. In order to measure the transverse position with
the longitudinal momentum simultaneously we can consider the polarized nucleon state in the
transverse direction which leads to distorted unpolarized ipdpdf in the tranverse plane [14, 15].
Distortion obtained in the transverse plane also leads to single spin asymmetries (SSA) and it has
been shown that such asymmetries can be explained by final state interactions (FSI) [16, 17, 18].
This mechanism gives us a good interpretation of SSAs which arises from the asymmetry (leftright) of quarks distribution in impact parameter space.
To study the GPDs, we use light front wave functions (LFWFs) which give a very simple
representation of GPDs. Impact parameter dependent parton distribution functions have been investigated by using the explicit LFWFs for the two-particle Fock state of the electron in QED
[19, 20]. In our case we take ζ = 0 [21, 22] which represents the momentum transfer exclusively in
transverse direction leading to the study of ipdpdfs in transverse impact parameter space. For the
case of spin flip GPD E(x, 0, −~∆2⊥ ), the parton distribution is distorted in the transverse plane when
the target has a transverse polarization and when integrated over x, E(x, 0, −~∆2⊥ ) yields the Pauli
form factor F2 (t). The sign of distortion can be concluded from the sign of the magnetic moment of
the nucleon. We extend the calculations to unintegrated momentum space distribution which is the
another direct way to determine the sign of distortion in impact parameter space from the LFWFs.
2. Generalized Parton Distributions (GPDs)
The GPDs H, E are defined through matrix elements of the bilinear vector currents on the light
cone:
dy− ixP+ y− /2 ′
e
hP |ψ¯ (0)γ + ψ (y)|Pi|y+ =0,y⊥ =0
8π
1
i +α
= ¯+ U¯ (P′ )[H(x, ζ ,t)γ + + E(x, ζ ,t)
σ (−∆α )]U (P).
2M
2P
Z
2
(2.1)
UG-FT-314/14
CAFPE-184/14
RM3-TH/14-16
arXiv:1410.3208v1 [hep-ph] 13 Oct 2014
A new physics interpretation of the IceCube data
Jos´e Ignacio Illanaa , Manuel Masipa , Davide Melonib
a
CAFPE and Departamento de F´ısica Te´orica y del Cosmos
Universidad de Granada, E-18071 Granada, Spain
b
Dipartimento di Matematica e Fisica
Universit`a di Roma Tre, I-00146 Rome, Italy
jillana@ugr.es, masip@ugr.es, meloni@fis.uniroma3.it
Abstract
IceCube has recently observed 37 events of TeV–PeV energies. The angular distribution, with a strong preference for downgoing directions, the spectrum, and the small
muon to shower ratio in the data can not be accommodated assuming standard interactions of atmospheric neutrinos. We obtain an excellent fit, however, if a diffuse flux
of ultrahigh energy (cosmogenic) neutrinos experiences collisions where only a small
fraction of the energy is transferred to the target nucleon. We show that consistent
models of TeV gravity or other non-Wilsonian completions of the standard model provide cross sections with these precise features. An increased statistics could clearly
distinguish our scenario from the one assumed by IceCube (a diffuse flux of astrophysical neutrinos with a ∝ E −2 spectrum) and establish the need for new physics in the
interpretation of the data.
Multivacuum States in a Fermionic Gap Equation with massive gluons and
confinement
R. M. Capdevilla
arXiv:1410.3184v1 [hep-ph] 13 Oct 2014
Physics Department, University of Notre Dame, South Bend, IN, United States and
Instituto de Fisica Teorica, Universidade Estadual Paulista - UNESP, Sao Paulo, SP, Brasil
We study the nontrivial solutions of the QCD fermionic gap equation including the contribution
of dynamically massive gluons and the confining propagator proposed by Cornwall. Without the
confining propagator, in the case of non-running gluon mass (mg ), we found the multivacuum
solutions (replicas) reported in the literature and we were able to define limits on mg for dynamical
chiral symmetry breaking. On the other side, when considering the running in the gluon mass the
vacuum replicas are absent in the limits on mg where the chiral symmetry is broken. In the pure
confining sector, the multivacuum states are always absent so it is said that only one stable solution
for the gap equation is found as claimed in previous analysis using different approaches. Finally in
the case of the complete gap equation i.e. with both contributions, the vacuum replicas are also
absent in both cases; with constant and with running gluon mass.
I.
INTRODUCTION
In Quantum Chromodynamics (QCD) the fundamental degrees of freedom of the theory are not detected as
free objects and the quark self-energy can drive the appearance of a dynamical mass. These two phenomena are
known as confinement of quarks and gluons and dynamical chiral symmetry breaking (CSB), respectively. When
studied separately, both phenomena are partially understood: For the latter, the idea is well accepted that the
chiral condensate obtain a nontrivial vacuum expected
value leading to the generation of a non-zero dynamical quark mass. In this scheme, the (pseudo)Goldstone
bosons associated with the breaking of the continuous
symmetry are the pions. One theoretical tool used to
study this process is the fermionic gap equation (FGE)
which can be obtained from the Schwinger-Dyson equations (SDE) for the fermionic fields [1]. In the case of
confinement, an order parameter used to describe the
transition from the confined to the deconfined phase is
the vacuum expectation value of the Polyakov loop L
[2, 3]. Although this description is well suited only for
pure gluons QCD, there are some modern approaches
with the aim of including quarks [4, 5].
Despite the advances in the understanding of both phenomena, one of the actual challenges for a complete description of the nonperturbative QCD regime is the connection between those important phases of the IR behavior of QCD. For example, it has been found that the deconfinement transition and the chiral symmetry restoration occur approximately at the same temperature for
quarks in the fundamental representation [6, 7], which is
different for the adjoint representation [8, 9]. The analysis of this behavior has been recently explored [10] in
the framework of the gap equation with the inclusion of
Cornwall’s confining propagator which has been shown
to provide a good description of the discrepancy between
the chiral transition of fundamental and adjoint quarks.
Another issue which concerns the relation of confinement
and chiral symmetry breaking is the idea that removal of
central vortices, may or may not impact in the recovery
of the chiral symmetry. It was found that at least for
SU (2) this condition is satisfied [11], however calculations for SU (3) are not yet conclusive [12].
The authors in reference [13], using a Hamiltonian approach to QCD in Coulomb gauge, report that the two
dimensional QCD possesses only one possible vacuum
state, given by the solution of the mass-gap equation,
while the four-dimensional theory possesses an excited
vacuum replica. Those results and a theoretical framework are explored in successive works [14, 15]. These
authors also suggest that for the pure linearly rising potential, the interaction is not strong enough to hold any
replicas so that “only one chirally nonsymmetric solution
to the mass-gap equation may exist” [13]. Furthermore,
the authors of reference [16] studied the fermionic gap
equation for pure QCD and they argue that the excited
vacuum states are a consequence of the nature of the gap
equation, since it is an integral equation. However, they
also show that this vacuum states do not affect what we
know about the hadronic spectrum. A quite similar analysis is performed in reference [17] but for QED3 in which
oscillatory solutions are found for the gap equation, solutions which are characterized by the number of zeros.
Nowadays the idea that nonperturbative effects can
drive massive propagators for the gauge bosons as suggested by Cornwall [18] is well accepted, especially because this result has been confirmed by lattice simulations [19, 20] and modern approaches using the DysonSchwinger equations [21, 22]. The consequence of the inclusion of massive gluons in the analysis of chiral symmetry breaking has been well explored, so that it is known
that for the accepted value [18] of the dynamical gluon
mass mg ≈ 2ΛQCD (being ΛQCD the QCD scale), the
fermionic gap equation is too weak to allow the CSB for
quarks in the fundamental representation [23–25]. Also,
the positivity issues discussed in reference [26] show that
mg > 1.2ΛQCD , values for which CSB is not yet achieved
with the standard fermionic gap equation. As a solution
to this issue, Cornwall proposed [27] a modification of
UTTG-20-14, TCC-022-14
Lepton-Flavored Asymmetric Dark Matter and Interference in Direct Detection
Ali Hamze,1 Can Kilic,1 Jason Koeller,1 Cynthia Trendafilova,1 and Jiang-Hao Yu1
arXiv:1410.3030v1 [hep-ph] 11 Oct 2014
1
Theory Group, Department of Physics and Texas Cosmology Center,
The University of Texas at Austin, Austin, TX 78712 U.S.A.
In flavored dark matter models, dark matter can scatter off of nuclei through Higgs and photon
exchange, both of which can arise from renormalizable interactions and individually lead to strong
constraints from direct detection. While these two interaction channels can destructively interfere
in the scattering amplitude, for a thermal relic with equal abundances for the dark matter particle
and its antiparticle, this produces no effect on the total event rate. Focusing on lepton-flavored dark
matter, we show that it is quite natural for dark matter to have become asymmetric during highscale leptogenesis, and that in this case the direct detection bounds can be significantly weakened
due to interference. We quantify this by mapping out and comparing the regions of parameter space
that are excluded by direct detection for the symmetric and asymmetric cases of lepton-flavored
dark matter. In particular, we show that the entire parameter region is ruled out for symmetric
dark matter, while large portions of parameter space are still allowed for the asymmetric case, when
dark matter is a scalar and the coupling to leptons dominates over the coupling to the Higgs, as
well as when dark matter is a fermion and the coupling to the Higgs dominates over the coupling
to leptons.
I.
INTRODUCTION
The steady improvement in the sensitivity of direct
detection searches is putting severe constraints on the
parameter space of dark matter (DM) models belonging to the weakly interacting massive particle (WIMP)
paradigm. These bounds can be relaxed in certain classes
of models, including Majorana fermion DM where only
spin-dependent scattering contributes, inelastic DM [1–
3] where the observed event rate is severely reduced due
to the energy cost of upscattering, or isospin violating
DM[4, 5] where destructive interference can occur between the scattering of DM off of protons and neutrons,
among others. The idea of destructive interference in the
scattering amplitude has been used in several dark matter
models in the past [6–15]. A simple class of models that
can give rise to interference is when the DM particle interacts with nuclei via multiple mediators. A non-trivial
check in such models is whether the parameters of the
model need to be fine-tuned, or in other words, whether
scattering amplitudes for the exchange of the mediators
are naturally of the same size for generic values of the
couplings in the model.
In this paper we argue that flavored dark matter
(FDM) models [16–23] can give rise to interference in
the scattering amplitude quite naturally. These models
admit renormalizable couplings between the DM and SM
fields that lead to both tree-level Higgs exchange as well
as loop-level photon exchange channels for direct detection, with comparable sizes.
Unfortunately, interference between spin-0 (Higgs) and
spin-1 (photon) mediated channels will not in general
help to ease direct detection constraints for WIMPs,
which have equal relic abundances for the DM particle
χ and its antiparticle χ.
¯ The amplitude for a spin-0 exchange channel will have the same sign for χ and χ,
¯ while
the amplitude for a spin-1 exchange channel will change
sign. Therefore, any destructive interference that occurs
for the scattering of χ off of nuclei will unavoidably lead
to constructive interference in the scattering of χ,
¯ and the
total scattering rate will be the same as in the absence
of any interference.
On the other hand, for asymmetric DM [24–30], the
destructive interference can significantly weaken direct
detection constraints. Interestingly, this too can occur
readily in FDM models. In this paper we focus on the
case of lepton-flavored DM, where we will show that it is
very natural for a DM asymmetry to be generated during high-scale leptogenesis [31] (for additional references
see reviews on this subject, e.g. [32, 33]). Using leptonflavored asymmetric DM as our benchmark model, and
contrasting with the same model but with a symmetric
χ-χ
¯ abundance, we will quantify the impact of interference on the region of parameter space that is compatible
with the null results of direct detection experiments. In
particular, we will show that for the case of scalar DM
that couples predominantly to leptons and for the case of
fermion dark matter that couples predominantly to the
Higgs, the symmetric case is completely ruled out due to
direct detection, while the asymmetric case can be consistent with the bounds due to interference.
The particle content of FDM models includes three
copies of the DM particle χ as well as a mediator particle φ which makes renormalizable interactions between χ
and the standard model (SM) fermions possible. Due to
Lorentz invariance, one of χ and φ is necessarily a fermion
while the other one is a boson. We will study both possibilities for completeness and highlight the similarities as
well as the differences between them.
The outline of the paper is as follows: In section II we
will review the lepton-flavored DM model and describe
its general features, before introducing a mechanism by
which it can become asymmetric during high-scale leptogenesis. We will go over the direct detection prospects
of lepton-flavored DM in section III and we will map out
the excluded regions in the parameter space of the model
LU TP 14-36
MCNET-14-22
CERN-PH-TH-2014-190
FERMILAB-PUB-14-316-CD
DESY 14-178
SLAC-PUB-16122
arXiv:1410.3012v1 [hep-ph] 11 Oct 2014
October 2014
An Introduction to PYTHIA 8.2
Torbj¨orn Sj¨ostranda,∗, Stefan Askb,1 , Jesper R. Christiansena , Richard Corkea,2 ,
Nishita Desaic , Philip Iltend , Stephen Mrennae , Stefan Prestelf,g ,
Christine O. Rasmussena , Peter Z. Skandsh,i
a
Department of Astronomy and Theoretical Physics, Lund University,
S¨
olvegatan 14A, SE-223 62 Lund, Sweden
b
Department of Physics, University of Cambridge, Cambridge, UK
c
Institut f¨
ur Theoretische Physik, Universit¨
at Heidelberg,
Philosophenweg 16, D-69120 Heidelberg, Germany
d
Massachusetts Institute of Technology, Cambridge, MA 02139, USA
e
Fermi National Accelerator Laboratory, Batavia, IL 60510, USA
f
Theory Group, DESY, Notkestrasse 85, D-22607 Hamburg, Germany
g
SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
h
CERN/PH, CH–1211 Geneva 23, Switzerland
i
School of Physics, Monash University, PO Box 27, 3800 Melbourne, Australia
Abstract
The Pythia program is a standard tool for the generation of events in high-energy collisions, comprising a coherent set of physics models for the evolution from a few-body hard
process to a complex multiparticle final state. It contains a library of hard processes, models for initial- and final-state parton showers, matching and merging methods between hard
processes and parton showers, multiparton interactions, beam remnants, string fragmentation and particle decays. It also has a set of utilities and several interfaces to external
programs. Pythia 8.2 is the second main release after the complete rewrite from Fortran
to C++, and now has reached such a maturity that it offers a complete replacement for
most applications, notably for LHC physics studies. The many new features should allow
an improved description of data.
Keywords: event generators, multiparticle production, matrix elements, parton showers,
matching and merging, multiparton interactions, hadronisation
Corresponding author; e-mail address: torbjorn@thep.lu.se
Now at Winton Capital Management, Zurich, Switzerland
2
Now at Nordea Bank, Copenhagen, Denmark
∗
1
Preprint submitted to Computer Physics Communications
October 14, 2014
Photon-Photon interactions in proton-proton collisions
at the LHC.
arXiv:1410.2983v1 [hep-ph] 11 Oct 2014
Mateusz Dyndal
AGH Univ. of Science and Technology, Cracow, Poland
CEA Saclay, Irfu/SPP, Gif-sur-Yvette, France
Laurent Schoeffel
CEA Saclay, Irfu/SPP, Gif-sur-Yvette, France
Abstract
Photon-photon interactions represent an important class of physics processes
at the LHC, where quasi-real photons are emitted by both colliding protons.
These reactions can result in the exclusive production of a final state X,
p + p → p + p + X. When computing such cross sections, it has already been
shown that finite size effects of colliding protons are important to consider
for a realistic estimate of the cross sections. These first results have been
essential in understanding the physics case of heavy-ion collisions in the low
invariant mass range, where heavy ions collide to form an exclusive final
state like a J/Ψ vector meson. In this paper, our purpose is to present some
calculations that are valid also for the exclusive production of high masses
final states in proton-proton collisions, like the production of a pair of W
bosons or the Higgs boson. Therefore, we propose a complete treatment
of the finite size effects of incident protons irrespective of the mass range
explored in the collision. Our expectations are shown to be in very good
agreement with existing experimental data obtained at the LHC.
1. Introduction
A significant fraction of proton-proton collisions at large energies involves
quasi-real photon interactions, where the photons are emitted by both protons. The proton-proton collision is then transformed into a photon-photon
interaction and the protons are deflected at small angles. At the LHC, these
Preprint submitted to Physics Letters B
October 14, 2014
UK/14-06
Three-Loop Contributions to Hyperfine Splitting: Muon Loop
Light-by-Light Insertion and Other Closed Lepton Loops
Michael I. Eides∗
Department of Physics and Astronomy,
University of Kentucky, Lexington, KY 40506, USA
arXiv:1410.2930v1 [hep-ph] 11 Oct 2014
Valery A. Shelyuto†
D. I. Mendeleyev Institute for Metrology, St.Petersburg 190005, Russia
The muon and tauon light-by-light scattering contributions to hyperfine splitting
in muonium are calculated. These results conclude calculation of all hard three-loop
contributions to hyperfine splitting containing graphs with closed fermion loops. We
discuss the special role that the lepton anomalous magnetic moments play in these
calculations. The full result for all three-loop radiative-recoil corrections to hyperfine
splitting generated by the graphs with closed lepton loops is presented.
∗
†
Also at the Petersburg Nuclear Physics Institute, Gatchina, St.Petersburg 188300, Russia; Email address:
eides@pa.uky.edu, eides@thd.pnpi.spb.ru
Email address: shelyuto@vniim.ru
Typeset by REVTEX
2
I.
INTRODUCTION
Calculation of high order corrections to hyperfine splitting in muonium is a classic playground
of high precision bound state quantum electrodynamics. For many years theory and experiment
developed hand in hand, and the measurements of the hyperfine splitting (HFS) were the best
source for the precise value of the electron-muon mass ratio (see, e.g, reviews [1–3]. The current
experimental error of HFS in muonium is in the interval 16-53 Hz (1.2 − 3.6 × 10−8 ) [4, 5]. More
than ten years ago we declared reduction of the theoretical error of HFS in muonium to the level
of 10 Hz to be an achievable goal of the theoretical research [1, 2]. This goal became recently
even more pressing in view of a new high accuracy measurement of muonium HFS planned now
at J-PARC, Japan [6, 7]. The goal of this experiment is to reduce the experimental error by
an order of magnitude, to the level of a few parts per billion, what is below 10 Hz.
In order to reduce the theoretical error below 10 Hz one has to calculate single-logarithmic
eF ,
and nonlogarithmic in mass ratio hard radiative-recoil corrections of order α2 (Zα)(m/M)E
eF and α(Zα)2 (m/M)E
eF 1 .
as well as soft nonlogarithmic contributions of orders (Zα)3 (m/M)E
We have concentrated our efforts on calculation of hard radiative-recoil corrections of order
eF , and in recent years calculated all single-logarithmic and nonlogarithmic corα2 (Zα)(m/M)E
rection the HFS arising from the diagrams with closed lepton loops [8–17]. Below we will
present the details of the recent calculation of the last previously unknown light-by-light scattering contribution to HFS arising from the virtual muon and tauon loops2 . We will also discuss
radiative-recoil corrections connected with the anomalous magnetic moments and present comeF generated by the three-loop diagrams
plete results for all corrections of order α2 (Zα)(m/M)E
containing closed lepton loops.
II.
MUON AND TAUON LOOP LIGHT-BY-LIGHT INSERTIONS
A.
General Expressions and the Infrared Problems
+
FIG. 1. Diagrams with two-photon exchanges
Radiative insertions in the diagrams with two-photon exchanges in Fig. 1 generate all
eF . It is well known that in
three-loop diagrams for the contributions of order α2 (Zα)(m/M)E
any gauge invariant set of diagrams radiative insertions suppress integration momenta small
in comparison with the electron mass. As a result the characteristic integration momenta in
these diagrams are of order of the electron mass or higher, these are hard corrections. This
significantly simplifies calculations because then we can neglect momenta of the external wave
1
2
Here α is the fine structure constant, m and M are the electron and muon masses, respectively. Z = 1 is the
charge of the constituent muon, it is convenient to introduce it for classification of different contributions.
eF = (8/3)(Zα)4 (m/M )(mr /m)3 m, where mr = mM/(m+M ) is the reduced
The Fermi energy is defined as E
mass.
The results of this calculation were already reported in [17].
arXiv:1410.2902v1 [hep-ph] 10 Oct 2014
UCRHEP-T545
October 2014
Dark Matter with Flavor Symmetry
and its Collider Signature
Ernest Ma and Alexander Natale
Department of Physics and Astronomy, University of California,
Riverside, California 92521, USA
Abstract
The notion that dark matter and standard-model matter are connected through
flavor implies a generic collider signature of the type 2 jets + µ± + e∓ + missing
energy. We discuss the theoretical basis of this proposal and its verifiability at the
Large Hadron Collider.
Inclusive J/ψ and ψ(2S) production in pp collisions at
√
s = 7 TeV at forward rapidity with ALICE at LHC
Biswarup Paul (For the ALICE Collaboration)∗
Counts per 50 MeV/c2
2.5 < y < 4
χ2/ndf = 1.18
N J/ψ = 70752 ± 371
mJ/ψ = 3100.1 ± 0.4 MeV/c 2
σJ/ψ = 72.0 ± 0.4 MeV/c 2
104
N ψ (2S) = 1988 ± 126
10
102
2
2.5
3
3.5
4
4.5
5
M µµ (GeV/c2)
ALI−PUB−73172
pp s = 7 TeV, inclusive J/ψ , 2.5<y <4
1
10-1
T
d2σ/(dp dy ) (µb/(GeV/c))
FIG. 1: Opposite sign dimuon invariant mass
spectra, integrated over y (2.5 ≤ y ≤ 4.0) and pT
(0 ≤ pT ≤ 20 GeV/c) [2].
10-2
ALICE, Lint = 1.35 pb-1 ± 5%
10-3
ALICE, Lint = 15.6 nb-1 ± 5.5%
LHCb, Lint = 5.2 pb-1 ± 10%
Systematic uncertainty
BR syst. unc. not shown
10-4
10-5
0
2
4
6
8
10
12
14
16 18 20
p (GeV/c)
T
ALI−PUB−73180
FIG. 2: pT differential cross section of J/ψ [2].
ALICE µ+µ-, Lint = 1.35 pb-1 ± 5%
ALICE µ+µ-, Lint = 15.6 nb-1 ± 5.5%
+
ALICE e e-, Lint = 5.6 nb-1 ± 4%
LHCb, Lint = 5.2 pb-1 ± 10%
Systematic uncertainty
BR syst. unc. not shown
12
10
8
6
4
pp s = 7 TeV, inclusive J/ψ
2
0
-5
-4
-3
-2
-1
0
1
2
3
4
ALI−PUB−73187
5
y
FIG. 3: y differential cross section of J/ψ [2].
address: biswarup.paul@cern.ch
d2σψ (2S)/(dp Tdy )
1
pp s = 7 TeV, inclusive ψ (2S)
-1
10
d2σJ/ψ /(dp Tdy )
duction. The production cross sections of J/ψ
and ψ(2S) were determined by normalizing the
production yields (the measured yields from
0.7
ALICE, inclusive J/ ψ , ψ (2S), 2.5<y <4
Lint = 1.35 pb-1
LHCb, prompt J/ψ , ψ (2S), 2<y <4.5
Lint(J/ψ ) = 5.2 pb-1, Lint(ψ (2S)) = 36 pb-1
0.6
0.5
0.4
T
d2σ/(dp dy ) (µb/(GeV/c))
∗ Electronic
pp s = 7 TeV, Lint = 1.35 pb-1
0 < p T < 20 GeV/c
105
3
dσ/dy (µb)
The ALICE detector is described in detail in [1]. The Muon Spectrometer of ALICE
is designed to measure the ψ and Υ states
(J/ψ,ψ(2S) and Υ(1S),Υ(2S),Υ(3S)) in the
forward pseudo-rapidity interval of −4 ≤ η ≤
−2.5.
The
√ present analysis uses pp collisions data
at s = 7 TeV. The data were recorded in
2011 with a trigger defined by the coincidence
of a minimum bias trigger with the detection
of two opposite sign muons reconstructed in
the trigger chambers of the muon spectrometer. A total of 4 million events were analysed, corresponding to an integrated luminosity Lint = 1.35 pb−1 (with 5% systematic uncertainty). In order to improve the purity of
the muon tracks the following selection criteria were applied: (1) both muon tracks match
with trigger tracks above the 1 GeV/c pT
threshold, (2) both muon tracks in the pseudorapidity range −4 ≤ η ≤ −2.5, (3) transverse radius coordinate of the track at the end
of the absorber (longitudinal position of absorber from interation point (IP) is −5.0 ≤ z
≤ −0.9 m) in the range 17.6 ≤ Rabs ≤ 89.5
cm. (4) dimuon rapidity in the range 2.5 ≤ y
≤ 4.0. (5) dimuon pT in the range 0 ≤ pT ≤
20 GeV/c.
Fig. 1 shows the invariant mass spectra fitted with two Extended Crystal Ball functions
(Crystal Ball function with a non gaussian tail
on both sides) for two signals and a variable
width gaussian function (a gaussian function
with a width varying linearly with the mass)
for the background.
We present here inclusive production of J/ψ
and ψ(2S). Inclusive measurements contain,
on top of the direct production, contributions
from the decay of higher excited states as
well as contributions from non-prompt pro-
Systematic uncertainty
BR syst. unc. not shown
-2
10
0.3
10
10-4
0.2
ALICE, 2.5<y <4, Lint = 1.35 pb-1 ± 5%
LHCb, 2<y <4.5, Lint = 36 pb-1 ± 1.3%
Systematic uncertainty
BR syst. unc. not shown
-3
0
2
4
6
8
10
0.1
12
T
0
2
4
6
8
10
12
p (GeV/c)
T
FIG. 6: ψ(2S)/J/ψ ratio as a function of pT [2].
0.35
dσψ (2S)/dy
dσJ/ψ /dy
1.6
1.2
pp s = 7 TeV
ALI−PUB−73212
FIG. 4: pT differential cross section of ψ(2S) [2].
1.4
0
14
16
p (GeV/c)
ALI−PUB−73197
dσ/dy (µb)
arXiv:1410.3075v1 [nucl-ex] 12 Oct 2014
Saha Institute of Nuclear Physics, Kolkata - 700064, India
ALICE, Lint = 1.35 pb-1 ± 5%
Systematic uncertainty
BR syst. unc. not shown
0.3
0.25
1
ALICE, inclusive J/ ψ , ψ (2S), L = 1.35 pb-1
int
Systematic uncertainty
BR syst. unc. not shown
0.2
0.8
0.15
0.6
0.4
0.1
pp s = 7 TeV, inclusive ψ (2S)
0
-5
ALI−PUB−73204
pp s = 7 TeV
0.05
0.2
-4
-3
-2
-1
0
1
2
3
4
5
y
0
2.6
2.8
3
3.2
3.4
3.6
3.8
4
y
ALI−PUB−73219
FIG. 5: y differential cross section of ψ(2S) [2].
FIG. 7: ψ(2S)/J/ψ ratio as a function of y [2].
the fits to the invariant mass spectra were
corrected by the acceptance times efficiency
factor) with the branching ratio and the integrated luminosity. The systematic uncertainties on the cross sections arise due to signal
extraction, MC parametrization, trigger and
tracking efficiency, matching efficiency and luminosity determinations.
The measured production cross sections of
J/ψ and ψ(2S), integrated in the y and pT
range are:
σJ/ψ = 6.69 ± 0.04 (stat.) ± 0.63 (syst.) µb.
σψ(2S) = 1.13 ± 0.07 (stat.) ± 0.19 (syst.) µb.
Fig. 2 and Fig. 3 show the differential production cross section of J/ψ in thirteen pT bins
and in six y bins, respectively. This result is
consistent with the previous ALICE result [3]
and also with the measurement performed by
the LHCb collaboration [4]. This measurement extends J/ψ cross section to 20 GeV/c
in pT at forward rapidity.
Fig. 4 shows the differential production
cross section of ψ(2S) in nine pT bins. The result is consistent with LHCb measurement [5]
in the same rapidity interval. Fig. 5 shows the
differential production cross sections of ψ(2S)
in six y bins. This is the first ψ(2S) measurement in pp collisions at ALICE.
The inclusive ψ(2S)/J/ψ ratio, integrated
over pT and y is 0.170 ± 0.011 (stat.) ±
0.013 (syst.). The ψ(2S)/J/ψ ratio were measured as a function of pT and y as shown in
Fig. 6 and Fig. 7 and a clear pT dependence
can be observed, in consistent with LHCb [5].
No strong y dependence is visible, in the y
range covered by the ALICE muon spectrometer. More details of this analysis can be found
in [2].
References
[1] K. Aamodt et al., (ALICE Collaboration)
J. Instrum. 3, S08002 (2008).
[2] B. Abelev et al., (ALICE Collaboration)
Eur.Phys.J. C74, 2974 (2014).
[3] K. Aamodt et al., (ALICE collaboration)
Phys. Lett. B704, 442-455 (2011).
[4] R. Aaij et al., (LHCb collaboration)
Eur.Phys.J. C71, 1645 (2011).
[5] R. Aaij et al., (LHCb collaboration)
Eur.Phys.J. C72, 2100 (2012).