GPS Timing and Control System of the HAWC Detector. A. U. Abeysekara

arXiv:1410.6681v1 [astro-ph.IM] 24 Oct 2014
GPS Timing and Control System of the HAWC
A. U. Abeysekara∗a,b , T. N. Ukwattaa , D. Edmundsa , J. T. Linnemanna , A.
Imranc , G. J. Kunded , I. G. Wisherc
Department of Physics and Astronomy, Michigan State University, East Lansing, MI,
Department of Physics and Astronomy, University of Utah, Salt Lake City, UT, USA
Wisconsin IceCube Particle Astrophysics Center (WIPAC) and Department of Physics,
University of Wisconsin-Madison, Madison, WI, USA
Physics Division, Los Alamos National Laboratory, Los Alamos, NM, USA
The design and performance of the GPS Timing and Control (GTC) System
of the High Altitude Water Cerenkov (HAWC) gamma ray observatory is
described. The GTC system provides a GPS synchronized absolute timestamp, with an accuracy better than 1µs, for each recorded event in HAWC.
In order to avoid any slack between the recorded data and the timestamp,
timestamps are injected to the main data acquisition (DAQ) system after
the Front-end Electronic Boards (FEBs). When HAWC is completed, the
HAWC main DAQ will use 10 time to digital converters (TDCs). In order to
keep all the TDCs in sync, the GTC system provides a synchronized clock
signal, coordinated trigger signal, and control signals to all TDCs.
GPS timestamp, gamma-ray astrophysics, water cherenkov detector, time
to digital converter, TeV astronomy
1 Introduction
2 HAWC Observatory
Corresponding author: [email protected]
Preprint submitted to NIM
October 27, 2014
Latest results of NEXT-DEMO, the prototype of the NEXT 100 double beta
decay experiment
L. Serraa,∗, D. Lorcaa , J. Mart´ın-Alboa , M. Sorela , J.J. G´omez-Cadenasa , on behalf of the NEXT Collaboration
de F´ısica Corpuscular (IFIC), CSIC & Universidad de Valencia
NEXT-DEMO is a 1:4.5 scale prototype of the NEXT100 detector, a high-pressure xenon gas TPC that will search
for the neutrinoless double beta decay of 136 Xe. X-ray energy depositions produced by the de-excitation of Xenon
atoms after the interaction of gamma rays from radioactive sources have been used to characterize the response of the
detector obtaining the spatial calibration needed for close-to-optimal energy resolution. Our result, 5.5% FWHM at
30 keV, extrapolates to 0.6% FWHM at the Q value of 136 Xe. Additionally, alpha decays from radon have been used
to measure several detection properties and parameters of xenon gas such as electron-ion recombination, electron drift
velocity, diffusion and primary scintillation light yield. Alpha spectroscopy is also used to quantify the activity of
radon inside the detector, a potential source of background for most double beta decay experiments.
Keywords: time projection chamber, x-ray, alpha decay, double beta decay, NEXT
1. The NEXT-DEMO prototype
scintillation (S1)
electroluminescence (S2)
NEXT-100 is a 100-kg high-pressure xenon gas electroluminescent TPC [1]. It will search for the neutrinoless double beta decay of 136 Xe in the Laboratorio
Subterr´aneo de Canfranc (LSC). The features that make
NEXT a powerful ββ0ν experiment are very good energy resolution, tracking capabilities and scalability to
large detector masses.
arXiv:1410.6700v1 [physics.ins-det] 24 Oct 2014
a Instituto
Figure 1: The NEXT detector concept. A plane of PMTs lo-
cated behind a transparent cathode detects both S1 and S2 signal measuring start of event time and the energy of event. On
the other side, a plane of SiPMs detects the forward EL light,
providing topological information of the event.
∗ Corresponding
author e-mail: [email protected]
NEXT-DEMO is a 1-kg prototype built to demonstrate the detector concept to be used in NEXT 100,outlined in Fig. 1. The xenon active volume of the TPC
comprises a 30 cm drift region, operated at a drift voltage between 200-1000 V · cm−1 and a 0.5 cm EL region
with a reduced electric field of 1-2 kV · cm −1 · bar−1 .
The pressure is 10 bar for all the studies presented here.
It has been running for 3 years using different radioactive sources. Some measurements made so far include energy resolution, imaging of single and double
electron tracks and xenon gas properties (drift velocity,
diffusion) [2, 3, 4, 5, 6].
2. Studies with electromagnetic depositions
X-ray depositions have been used to determine the
energy response of the TPC, needed to achieve the goal
energy resolution [5]. XY energy response has been
measured in the active volume of the detector in order
to homogenize the response in the energy plane.
Drift velocity is obtained by studying the temporal
distribution of these events, shown in Fig. 2. Using the
primary scintillation we are able to measure the drift
time of the electrons coming from the cathode, the full
drift length, and obtain the drift velocity. Results are
consistent with previous measurement using alpha particle depositions [6]. In addition, these events are used
Backgrounds and sensitivity of the NEXT double beta decay experiment
M. Nebot-Guinota,∗, P. Ferrarioa , J. Mart´ın-Alboa , J. Mu˜noz Vidala , J.J. G´omez-Cadenasa ,
on behalf of the NEXT Collaboration
de F´ısica Corpuscular (IFIC), CSIC & Universitat de Val`encia
Calle Catedr´atico Jos´e Beltr´an, 2, 46980 Paterna, Valencia, Spain
arXiv:1410.6699v1 [physics.ins-det] 24 Oct 2014
a Instituto
NEXT (Neutrino Experiment with a Xenon TPC) is a neutrinoless double-beta (ββ0ν) decay experiment that will
operate at the Canfranc Underground Laboratory (LSC). It is an electroluminescent high-pressure gaseous xenon
Time Projection Chamber (TPC) with separate read-out planes for calorimetry and tracking. Energy resolution and
background suppression are the two key features of any neutrinoless double beta decay experiment. NEXT has both
good energy resolution (< 1% FWHM) at the Q value of 136 Xe and an extra handle for background identification
provided by track reconstruction. With the background model of NEXT, based on the detector simulation and the
evaluation of the detector radiopurity, we can determine the sensitivity to a measurement of the ββ2ν mode in NEW
and to a ββ0ν search in NEXT100. In this way we can predict the background rate of 5 × 10−4 counts/(keV kg yr),
and a sensitivity to the Majorana neutrino mass down to 100 meV after a 5-years run of NEXT100.
Keywords: time projection chamber, radioactivity, background, double beta decay, NEXT
1. Neutrinoless double beta decay
Neutrinoless double beta decay (ββ0ν) is a postulated
nuclear transition in which two neutrons undergo β decay simultaneously without the emission of neutrinos.
Evidence of this process would establish that massive
neutrinos are Majorana particles, provide a hint of a new
physics scale beyond the Standard Model and prove the
violation of total lepton number, a key element to explain the observed asymmetry between matter and antimatter in the universe. In addition, the measurement of
the ββ0ν-decay rate would provide information on the
absolute scale of neutrino masses [1], as shown in Eq.1:
0ν −1
T 1/2
∝ m2ββ
2. Double beta decay experiments
Double beta decay detectors measure the sum of the
kinetic energies from the two released electrons, Qββ.
Considering the finite energy resolution (∆E) of any detector, other processes occurring in the detector, as the
tail of the ββ2ν mode, can fall in the region of energies around Qbb becoming background. As in other rare
∗ Corresponding
author e-mail: [email protected]
event detectors, backgrounds of cosmogenic origin and
natural radioactivity from materials are a problem, and
thus underground operation and selection of radiopure
materials is essential. In this sense additional experimental features are desired to improve the sensitivity
of the detector, such as extra background (B) rejection,
better detector efficiency () or larger exposure (M · t)
[1]. This relation can be summarized as follows :
T 1/2 ∝ a · (2)
∆E · B
3. NEXT-100
The NEXT-100 detector will search for the neutrinoless double beta decay of 136 Xe at the Laboratorio Subterraneo de Canfranc. It uses a time projection chamber
filled with 100 kg of enriched xenon gas at 15 bar pressure, with separated detection functions for calorimetry
and tracking [2]. The gaseous xenon provides scintillation and ionization as primary signals. These are used
to establish the start-of-event time (t0 ) and for calorimetry/tracking respectively. In order to achieve optimal
energy resolution, the ionization signal is amplified in
NEXT using the electroluminescence (EL) of xenon [3].
Calorimetry : The energy plane is made of 60 photomultiplier tubes (Hamamatsu R11410-10 PMTs), lo-
Preprint typeset in JINST style - HYPER VERSION
arXiv:1410.6496v1 [physics.ins-det] 23 Oct 2014
Scalability, scintillation readout and charge drift in a
kilogram scale solid xenon particle detector
J. Yoo∗, H. Cease, W. F. Jaskierny, D. Markley, and R. B. Pahlka
Fermi National Accelerator Laboratory, Kirk and Pine St., Batavia, IL 60510, USA
D. Balakishiyeva and T. Saab
Department of Physics, University of Florida, Gainesville, FL 32611, USA
M. Filipenko
Erlangen Center for Astroparticle Physics (ECAP), Friedrich Alexander University of
Erlangen-Nuremberg, Erwin-Rommel-Stra¨sse 1, 91058 Erlangen, Germany
A BSTRACT: We report a demonstration of the scalability of optically transparent xenon in the solid
phase for use as a particle detector above a kilogram scale. We employ a liquid nitrogen cooled
cryostat combined with a xenon purification and chiller system to measure the scintillation light
output and electron drift speed from both the solid and liquid phases of xenon. Scintillation light
output from sealed radioactive sources is measured by a set of high quantum efficiency photomultiplier tubes suitable for cryogenic applications. We observed a reduced amount of photons in solid
phase compared to that in liquid phase. We used a conventional time projection chamber system
to measure the electron drift time in a kilogram of solid xenon and observed faster electron drift
speed in the solid phase xenon compared to that in the liquid phase.
K EYWORDS : Solid-noble element detector, scintillators, charge transport.
∗ Corresponding
Author: [email protected]
Nuclear Physics B
Nuclear Physics B Proceedings Supplement 00 (2014) 1–7
SUSY fits with full LHC Run I data
Kees Jan de Vries (on behalf of the MasterCode Collaboration)a
arXiv:1410.6755v1 [hep-ph] 24 Oct 2014
a High
Energy Physics Group, Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2AZ, UK
We present the latest results from the MasterCode collaboration on supersymmetric models, in particular on the
CMSSM, the NUHM1, the NUHM2 and the pMSSM. We combine the data from LHC Run I with astrophysical
observables, flavor and electroweak precision observables. We determine the best fit regions of these models and
analyze the discovery potential of squarks and gluinos at LHC Run II and direct detection experiments.
Keywords: Supersymmetry, CMSSM, NUHM1, NUHM2, pMSSM
1. Introduction
Despite the absence of any convincing signal of supersummetry (SUSY) after Run 1 at the large hadron
collider (LHC), SUSY remains well motivated. First
of all, the lightest neutralino is a natural DM candidate. Secondly, SUSY provides a solution to the hierarchy problem. Finally, SUSY allows for unification of
the gauge coupling at the so-called grand unified theory
(GUT) scale of O(1016 GeV).
In these proceedings we present a selection of the results from global frequentist fits of constrained models of SUSY - the CMSSM, NUHM1, NUHM2 and
pMSSM10 (defined below) - to experimental constraints from Run I LHC data, astrophysical observables, flavor and electroweak observables. The fits allow us to identify the relevant parameters, assess and
compare the validity of the models and study the predictions and consequences for future searches and experiments. In particular, we focus on the differences between GUT-scale and phenomenological models highlighting the (g−2)µ constraint. We discuss the discovery
potential for gluinos and squarks at LHC Run II as well
as prospects for direct detection of dark matter.
Note that the results presented in these proceedings
date from the ICHEP2014 conference. We have published elsewhere some of the results shown in these
proceedings, namely on the CMSSM, NUHM1 and
NUHM2 [1, 2]. We would also like to mention that
there are several other groups that perform global fits of
SUSY using Bayesian as well as frequentist methods.
Some recent fits of CMSSM, NUHM1 and NUHM2
may be found in [3–6], whereas results on the pMSSM
may be found in [7, 8]. We will soon publish updated
results on pMSSM10.
2. Analysis procedure
2.1. Models
We consider four constrained versions of the general R-parity-conserving Minimal Supersymmetric extension of the Standard Model (MSSM). Three of these
models are derived from GUT model-building considerations, where masses and couplings are assumed to
unify at the GUT scale: In the constrained MSSM
(CMSSM) all scalars (two Higgs doublets and the
sfermions) have a universal soft SUSY-breaking mass
m0 , the gauginos a universal mass m1/2 , and the trilinear
couplings are all equal to A0 . In the NUHM1 the masses
of the Higgs doublets are assumed to be independent but
equal, while in the NUHM2 they are allowed to vary independently. In general m20 can take negative values,
and so we denote in this paper m0 ≡ Sign(m20 ) |m20 | <
0. The remaining parameters of these models are the
superpotential coupling µ between the Higgs doublets
arXiv:1410.6753v1 [physics.pop-ph] 24 Oct 2014
The symmetry and simplicity of the
laws of physics and the Higgs boson
Juan Maldacena
Institute for Advanced Study, Princeton, NJ 08540, USA
We describe the theoretical ideas, developed between the 1950s-1970s, which led
to the prediction of the Higgs boson, the particle that was discovered in 2012. The
forces of nature are based on symmetry principles. We explain the nature of these
symmetries through an economic analogy. We also discuss the Higgs mechanism,
which is necessary to avoid some of the naive consequences of these symmetries, and
to explain various features of elementary particles.
What can radiative decays of the X(3872) teach us about its
Feng-Kun Guoa , C. Hanhartb , Yu.S. Kalashnikovac , Ulf-G. Meißnera,b , A.V. Nefedievc,d,e
arXiv:1410.6712v1 [hep-ph] 24 Oct 2014
Helmholtz-Institut f¨
ur Strahlen- und Kernphysik and Bethe Center for Theoretical Physics, Universit¨
Bonn, D-53115 Bonn, Germany
Forschungszentrum J¨
ulich, Institute for Advanced Simulation, Institut f¨
ur Kernphysik and J¨
ulich Center
for Hadron Physics, D-52425 J¨
ulich, Germany
Institute for Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117218 Moscow, Russia
National Research Nuclear University MEPhI, 115409, Moscow, Russia
Moscow Institute of Physics and Technology, 141700, Dolgoprudny, Moscow Region, Russia
¯ ∗ molecule, we discuss the radiative
Starting from the hypothesis that the X(3872) is a D D
decays of the X(3872) into γJ/ψ and γψ from an effective field theory point of view. We
show that radiative decays are not sensitive to the long-range structure of the X(3872). In
particular, contrary to earlier claims, we argue that the experimentally determined ratio of
the mentioned branching fractions is not in conflict with a wave function of the X(3872)
¯ ∗ hadronic molecular component.
that is dominated by the D D
Keywords: exotic hadrons, charmonium
1. Introduction
The X(3872) was discovered by the Belle Collaboration in 2003 [1]. It has a mass
¯ ∗0 threshold, and thus it has been regarded as one of the most
extremely close to the D 0 D
promising candidates for a hadronic molecule, which can be either an S-wave bound state [2–
¯ ∗ system [8]. Its quantum numbers were determined by the
7] or a virtual state in the D D
LHCb Collaboration to be J P C = 1++ [9] 10 years after the discovery.
Other models exist in addition to the hadronic molecule interpretation, which include
a radial excitation of the P -wave charmonium χc1 (2P ) [10], a tetraquark [11], a mixture
of an ordinary charmonium and a hadronic molecule [12, 13], or a state generated in the
coupled-channel dynamical scheme [14, 15]. It was claimed in Ref. [16] that the radiative
decays of the X(3872) into the γJ/ψ and γψ ′ (here and in what follows ψ ′ denotes ψ(2S))
are very sensitive to its structure. Especially, using vector meson dominance and a quark
model, in Ref. [16] it was predicted that the ratio
B(X(3872) → γψ ′ )
B(X(3872) → γJ/ψ)
is about 4 × 10−3 , if the X(3872) is a hadronic molecule with the dominant component
¯ ∗0 plus a small admixture of the ρJ/ψ and ωJ/ψ. Various quark model calculations
Preprint submitted to Physics Letters B
October 27, 2014
Progress in Double Parton Scattering Studies
Sunil Bansal,1 Paolo Bartalini* ,2 Boris Blok,3 Diego Ciangottini,4, 5 Markus Diehl,6
Fiorella M. Fionda,7, 8 Jonathan R. Gaunt,6 Paolo Gunnellini,4, 5 Tristan Du Pree,9 Tomas
Kasemets,10, 11 Daniel Ostermeier,12 Sergio Scopetta,4, 5 Andrzej Si´odmok,13 Alexander
M. Snigirev,14 Antoni Szczurek,15, 16 Daniele Treleani*,17, 18 and Wouter J. Waalewijn* 10, 19
Department of Physics, University of Antwerp, 2020 Antwerp, Belgium
Department of Physics, Central China Normal University, 430079 Wuhan, China
Department of Physics, Technion - Israel Institute of Technology, Haifa, Israel
Dipartimento di Fisica, Universit`
a degli Studi di Perugia, 06100 Perugia, Italy
INFN, sezione di Perugia, via A. Pascoli, 06100 Perugia, Italy
Theory Group, Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg, Germany
Dipartimento interateneo di Fisica, Universit`
a degli Studi di Bari, Via Amendola 173, 70126 Bari, Italy
INFN, sezione di Bari, Via E. Orabona n. 4, 70125 Bari, Italy
Universit´e Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium
Nikhef, Theory Group, Science Park 105, 1098 XG, Amsterdam, The Netherlands
Department of Physics and Astronomy, VU University,
De Boelelaan 1081, 1081 HV, Amsterdam, the Netherlands
Institut f¨
ur Theoretische Physik, Universit¨
at Regensburg, 93040 Regensburg, Germany
School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL, U.K.
Skobeltsyn Institute of Nuclear Physics, Moscow State University, 119991 Moscow, Russia
Institute of Nuclear Physics PAN, PL-31-342 Cracow, Poland
University of Rzesz´
ow, PL-35-959 Rzesz´
ow, Poland
Dipartimento di Fisica dellUniversit di Trieste, Trieste, Italy
INFN, Sezione di Trieste, Strada Costiera 11, Miramare-Grignano, I-34151 Trieste, Italy
ITFA, University of Amsterdam, Science Park 904, 1018 XE, Amsterdam, The Netherlands
(Dated: October 27, 2014)
arXiv:1410.6664v1 [hep-ph] 24 Oct 2014
An overview of theoretical and experimental progress in double parton scattering (DPS) is presented. The theoretical topics cover factorization in DPS, models for double parton distributions
and DPS in charm production and nuclear collisions. On the experimental side, CMS results for
dijet and double J/ψ production, in light of DPS, as well as first results for the 4-jet channel are
presented. ALICE reports on a study of open charm and J/ψ multiplicity dependence.
limitations and proper generalization of Eq. (1). This
is reflected in the variety of topics discussed within the
DPS track at this workshop:
• Progress in factorization for DPS
Theoretical predictions for double parton scattering
(DPS) require a factorization theorem for the cross section, in order to separate the two short-distance collisions
from the long-range physics of the incoming protons. The
partonic cross section of the hard scatterings is perturbatively calculable. The momenta of the quarks and gluons
inside the proton are described by non-perturbative (double) parton distribution functions (PDFs), which must be
modeled or extracted from data.
If the two hard scatterings are independent and the
two incoming partons in each proton are completely independent, the DPS cross section simplifies to
σ1 σ2
with σ1 and σ2 the standard cross sections of the individual scatterings and S a symmetry factor. This leaves a
single nonperturbative parameter σeff , which only affects
the total DPS rate. For certain applications this approximation is sufficient, but one would also like to know the
• Double parton correlations in proton models
• DPS in charm cross sections
• DPS in nuclear collisions
Progress in Factorization
A factorization analysis of DPS [1–3] reveals a large
number of effects that are not included in the “pocket
formula” in Eq. (1):
• Correlations between the two momentum fractions,
the transverse separation of partons and/or flavor
• Spin correlations between the partons
• Color correlations between the partons
• Interferences in fermion number
• Interferences in flavor
ULB-TH/14-15, LPN14-119, ZU-TH35/14, STUPP-14-220
LHC Tests of Light Neutralino Dark Matter
without Light Sfermions
Lorenzo Calibbi
arXiv:1410.5730v1 [hep-ph] 21 Oct 2014
? 1,
Jonas M. Lindert
† 2,
Toshihiko Ota
‡ 3,
Yasutaka Takanishi
∗ 4
Service de Physique Th´eorique, Universit´e Libre de Bruxelles,
Bld du Triomphe, CP225, B-1050 Brussels, Belgium
Physik-Institut, Universit¨
at Z¨
Wintherturerstrasse 190, CH-8057 Z¨
urich, Switzerland
Department of Physics, Saitama University,
Shimo-Okubo 255, 338-8570 Saitama-Sakura, Japan
Max-Planck-Institut f¨
ur Kernphysik,
Saupfercheckweg 1, D-69117 Heidelberg, Germany
We address the question how light the lightest MSSM neutralino can be as dark matter candidate in a scenario where all supersymmetric scalar particles are heavy. The
hypothesis that the neutralino accounts for the observed dark matter density sets strong
requirements on the supersymmetric spectrum, thus providing an handle for collider tests.
In particular for a lightest neutralino below 100 GeV the relic density constraint translates
into an upper bound on the Higgsino mass parameter µ in case all supersymmetric scalar
particles are heavy. One can define a simplified model that highlights only the necessary
features of the spectrum and their observable consequences at the LHC. Reinterpreting
recent searches at the LHC we derive limits on the mass of the lightest neutralino that,
in many cases, prove to be more constraining than dark matter experiments themselves.
[email protected]
[email protected]
[email protected]
[email protected]
arXiv:1410.6765v1 [hep-ex] 24 Oct 2014
Constraints on parton distribution functions and extraction
of the strong coupling constant from√
the inclusive jet cross
section in pp collisions at s = 7 TeV
The CMS Collaboration∗
The inclusive jet cross section for proton-proton collisions at a centre-of-mass energy
of 7 TeV was measured by the CMS Collaboration at the LHC with data corresponding
to an integrated luminosity of 5.0 fb−1 . The measurement covers a phase space up to
2 TeV in jet transverse momentum and 2.5 in absolute jet rapidity. The statistical precision of these data leads to stringent constraints on the parton distribution functions
of the proton. The data provide important input for the gluon density at high fractions of the proton momentum and for the strong coupling constant at large energy
scales. Using predictions from perturbative quantum chromodynamics at next-toleading order, complemented with electroweak corrections, the constraining power
of these data is investigated and the strong coupling constant at the Z boson mass MZ
is determined to be αS ( MZ ) = 0.1185 ± 0.0019 (exp) +
−0.0037 (theo), which is in agreement with the world average.
Submitted to the European Physical Journal C
c 2014 CERN for the benefit of the CMS Collaboration. CC-BY-3.0 license
∗ See
Appendix C for the list of collaboration members
arXiv:1410.6679v1 [hep-ex] 24 Oct 2014
Search for a standard model-like Higgs boson in the µ+ µ−
and e+ e− decay channels at the LHC
The CMS Collaboration∗
A search is presented for a standard model-like Higgs boson decaying to the µ+ µ−
or e+ e− final states based on proton-proton collisions recorded by the CMS experiment at the CERN LHC. The data correspond to integrated luminosities of 5.0 fb−1
at a centre-of-mass energy of 7 TeV and 19.7 fb−1 at 8 TeV for the µ+ µ− search, and of
19.7 fb−1 at 8 TeV for the e+ e− search. To enhance the sensitivity of the search, events
are categorized by topologies according to production process and dilepton invariant mass resolution. Upper limits on the production cross section times branching
fraction at the 95% confidence level are reported for Higgs boson masses in the range
from 120 to 150 GeV. For a Higgs boson with a mass of 125 GeV decaying to µ+ µ− ,
the observed (expected) upper limit on the production rate is found to be 7.4 (6.5+
−1.9 )
times the standard model value. This corresponds to an upper limit on the branching fraction of 0.0016. Similarly, for e+ e− , an upper limit of 0.0019 is placed on the
branching fraction, which is ≈3.7 × 105 times the standard model value. These results, together with recent evidence of the 125 GeV boson coupling to τ-leptons with
a larger branching fraction consistent with the standard model, show for the first time
that the leptonic couplings of the new boson are not flavour-universal.
Submitted to Physics Letters B
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:1410.6615v1 [hep-ex] 24 Oct 2014
Longitudinal target-spin asymmetries for deeply virtual Compton scattering
E. Seder,1, 2 A. Biselli,3 S. Pisano,4, 5 S. Niccolai,5, ∗ G.D. Smith,6, 7 K. Joo,1 K. Adhikari,8 M.J. Amaryan,8
M.D. Anderson,6 S. Anefalos Pereira,4 H. Avakian,9 M. Battaglieri,10 I. Bedlinskiy,11 J. Bono,12 S. Boiarinov,9
P. Bosted,9, 13 W. Briscoe,14 J. Brock,9 W.K. Brooks,15 S. B¨
ultmann,8 V.D. Burkert,9 D.S. Carman,9 C. Carlin,9
A. Celentano,10 S. Chandavar,16 G. Charles,5 L. Colaneri,17 P.L. Cole,18 M. Contalbrigo,19 D. Crabb,20 V. Crede,21
A. D’Angelo,17, 22 N. Dashyan,23 R. De Vita,10 E. De Sanctis,4 A. Deur,9 C. Djalali,24 D. Doughty,25, 9 R. Dupre,5, 26
L. El Fassi,8 L. Elouadrhiri,9 P. Eugenio,21 G. Fedotov,24, 27 S. Fegan,10, 6 A. Filippi,28 J.A. Fleming,7 A. Fradi,5
B. Garillon,5 M. Gar¸con,2 N. Gevorgyan,23 Y. Ghandilyan,23 K.L. Giovanetti,29 F.X. Girod,9, 2 J.T. Goetz,16
W. Gohn,1, † R.W. Gothe,24 K.A. Griffioen,13 B. Guegan,5 M. Guidal,5 L. Guo,12 K. Hafidi,26 H. Hakobyan,15, 23
C. Hanretty,20, ‡ N. Harrison,1 M. Hattawy,5 N. Hirlinger Saylor,30, § M. Holtrop,31 S.M. Hughes,7 Y. Ilieva,24
D.G. Ireland,6 B.S. Ishkhanov,27 E.L. Isupov,27 H.S. Jo,5 S. Joosten,32 C.D. Keith,9 D. Keller,20, 16
G. Khachatryan,23 M. Khandaker,18, 33 A. Kim,34, ¶ W. Kim,34 A. Klein,8 F.J. Klein,35 S. Koirala,8 V. Kubarovsky,9
S.E. Kuhn,8 P. Lenisa,19 K. Livingston,6 H.Y. Lu,24 I.J.D. MacGregor,6 N. Markov,1 M. Mayer,8 B. McKinnon,6
D.G. Meekins,9 T. Mineeva,1 M. Mirazita,4 V. Mokeev,9, 27 R. Montgomery,4 C.I. Moody,26 H. Moutarde,2
A Movsisyan,19 C. Munoz Camacho,5 P. Nadel-Turonski,9, 35 I. Niculescu,29 M. Osipenko,10 A.I. Ostrovidov,21
M. Paolone,32 L.L. Pappalardo,19 K. Park,9, 24, ∗∗ S. Park,21 E. Pasyuk,9, 36 P. Peng,20 W. Phelps,12 O. Pogorelko,11
J.W. Price,37 Y. Prok,8 D. Protopopescu,6 A.J.R. Puckett,1 M. Ripani,10 A. Rizzo,17 G. Rosner,6 P. Rossi,4, 9
P. Roy,21 F. Sabati´e,2 C. Salgado,33 D. Schott,14, 12 R.A. Schumacher,38 I. Senderovich,36 A. Simonyan,23
I. Skorodumina,24 D. Sokhan,6, 7 N. Sparveris,32 S. Stepanyan,9 P. Stoler,30 I.I. Strakovsky,14 S. Strauch,24
V. Sytnik,15 M. Taiuti,10, 39 W. Tang,16 Y. Tian,24 M. Ungaro,9, 1 H. Voskanyan,23 E. Voutier,40 N.K. Walford,35
D.P. Watts,7 X. Wei,9 L.B. Weinstein,8 M.H. Wood,41, 24 N. Zachariou,24 L. Zana,7 J. Zhang,9, 8 and I. Zonta17
(The CLAS Collaboration)
University of Connecticut, Storrs, Connecticut 06269
CEA, Centre de Saclay, Irfu/Service de Physique Nucl´eaire, 91191 Gif-sur-Yvette, France
Fairfield University, Fairfield, Connecticut 06824
INFN, Laboratori Nazionali di Frascati, 00044 Frascati, Italy
Institut de Physique Nucl´eaire Orsay, 91406 Orsay, France
University of Glasgow, Glasgow G12 8QQ, United Kingdom
Edinburgh University, Edinburgh EH9 3JZ, United Kingdom
Old Dominion University, Norfolk, Virginia 23529
Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606
INFN, Sezione di Genova, 16146 Genova, Italy
Institute of Theoretical and Experimental Physics, Moscow, 117259, Russia
Florida International University, Miami, Florida 33199
College of William and Mary, Williamsburg, Virginia 23187-8795
The George Washington University, Washington, D.C. 20052
Universidad T´ecnica Federico Santa Mar´ıa, Casilla 110-V Valpara´ıso, Chile
Ohio University, Athens, Ohio 45701
INFN, Sezione di Roma Tor Vergata, 00133 Roma, Italy
Idaho State University, Pocatello, Idaho 83209
INFN, Sezione di Ferrara, 44100 Ferrara, Italy
University of Virginia, Charlottesville, Virginia 22901
Florida State University, Tallahassee, Florida 32306
a di Roma Tor Vergata, 00133 Roma, Italy
Yerevan Physics Institute, 375036 Yerevan, Armenia
University of South Carolina, Columbia, South Carolina 29208
Christopher Newport University, Newport News, Virginia 23606
Argonne National Laboratory, Argonne, Illinois 60439
Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119234 Moscow, Russia
INFN, Sezione di Torino, Torino, Italy
James Madison University, Harrisonburg, Virginia 22807
Rensselaer Polytechnic Institute, Troy, New York 12180-3590
University of New Hampshire, Durham, New Hampshire 03824-3568
Temple University, Philadelphia, Pennsylvania 19122
Norfolk State University, Norfolk, Virginia 23504
Kyungpook National University, Daegu 702-701, Republic of Korea
Catholic University of America, Washington, D.C. 20064
Arizona State University, Tempe, Arizona 85287-1504
California State University, Dominguez Hills, Carson, California 90747
Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
a di Genova, 16146 Genova, Italy
LPSC, Universit´e Grenoble-Alps, CNRS/IN2P3, Grenoble, France
Canisius College, Buffalo, New York 14208
(Dated: October 27, 2014)
A measurement of the electroproduction of photons off protons in the deeply inelastic regime was
performed at Jefferson Lab using a nearly 6-GeV electron beam, a longitudinally polarized proton
target and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for ep → e0 p0 γ
events, which arise from the interference of the deeply virtual Compton scattering and the BetheHeitler processes, were extracted over the widest kinematics in Q2 , xB , t and φ, for 166 fourdimensional bins. In the framework of Generalized Parton Distributions (GPDs), at leading twist
the t dependence of these asymmetries provides insight on the spatial distribution of the axial charge
of the proton, which appears to be concentrated in its center. These results also bring important
and necessary constraints for the existing parametrizations of chiral-even GPDs.
PACS numbers: 12.38.-t, 13.40.-f, 13.60.-r, 25.30.-c, 25.30.Rw, 25.30.Dh, 25.30.Fj
Nearly 60 years after Hofstadter’s direct measurement
of the finite size of the proton [1], the way the bulk properties of the nucleon, such as its mass and spin, are connected to the dynamics of its constituents is still a subject
of intense research. Quantum Chromo-Dynamics (QCD),
the fundamental theory of the strong interaction, is still
unsolved for quarks confined in the nucleon. Therefore,
phenomenological functions need to be used to connect
experimental observables with the inner dynamics of the
constituents of the nucleons, the partons. The Generalized Parton Distributions (GPDs), introduced two
decades ago, have emerged as a universal tool to describe
hadrons, and nucleons in particular, in terms of their
elementary constituents, quarks and gluons [2–7]. The
GPDs combine and generalize the features of the form
factors measured in elastic scattering and of the parton
distribution functions obtained via deep inelastic scattering (DIS). In a reference frame in which the nucleon
moves at the speed of light, the GPDs correlate the longitudinal momentum and the transverse position of partons in a given helicity state. They can also give access
to the contribution to the nucleon spin from the orbital
angular momentum of the quarks, via Ji’s sum rule [4].
At leading order in the QCD coupling constant αs and at
leading twist (i.e. neglecting quark-gluon interactions or
higher-order quark loops), considering only quark GPDs
and quark-helicity conserving quantities, there are four
e E,
e which can
different GPDs for the nucleon: H, E, H,
be measured in exclusive electroproduction reactions at
corresponding author: [email protected]
Current address:University of Kentucky, Lexington, Kentucky
Current address:Thomas Jefferson National Accelerator Facility,
Newport News, Virginia 23606
Current address:University of Massachusetts, Amherst, Massachusetts 01003
Current address:University of Connecticut, Storrs, Connecticut
Current address:Old Dominion University, Norfolk, Virginia
FIG. 1. (Color online) The “handbag” diagram for the DVCS
process on the proton ep → e0 p0 γ. t = (p − p0 )2 is the squared
four-momentum transfer between the initial and final protons.
ξ is proportional to the Bjorken variable xB (ξ ' 2−x
, where
xB = 2M
, M is the proton mass and ν = Ee − Ee0 ). x is not
accessible experimentally in the DVCS process.
high electron-momentum transfer.
Deeply virtual Compton scattering (DVCS) (ep →
e0 p0 γ, Fig. 1) is the simplest process to access the GPDs
of the proton. At high γ ∗ virtuality Q2 = −(e − e0 )2 , and
at leading twist, which is valid at small squared momentum transfer to the proton −t relative to Q2 , this process
corresponds to the absorption of a virtual photon by a
quark carrying a fraction (x + ξ) of the longitudinal momentum of the proton with respect to its direction. The
struck quark emits a real photon, as a result of which
its final longitudinal momentum fraction is (x − ξ). The
amplitude for DVCS can be factorized [4] into a hardscattering part (calculable in perturbative QCD) and a
non-perturbative part, representing the soft structure of
the nucleon, parametrized by the GPDs that depend on
the three kinematic variables x, ξ, and t. The definitions
of the kinematic variables are in the caption of Fig. 1.
The Fourier transform, at ξ = 0, of the t dependence
of a GPD provides the spatial distribution in the transverse plane for partons having a longitudinal momentum
fraction x.
DVCS shares the same final state with the BetheHeitler (BH) process, where a real photon is emitted by
arXiv:1410.6538v1 [hep-ex] 24 Oct 2014
Study of e+ e− → ωχcJ at center-of-mass energies from 4.21 to 4.42 GeV
M. Ablikim1 , M. N. Achasov8,a , X. C. Ai1 , O. Albayrak4 , M. Albrecht3 , D. J. Ambrose42 , A. Amoroso46A,46C , F. F. An1 ,
Q. An43 , J. Z. Bai1 , R. Baldini Ferroli19A , Y. Ban30 , D. W. Bennett18 , J. V. Bennett4 , M. Bertani19A , D. Bettoni20A ,
J. M. Bian41 , F. Bianchi46A,46C , E. Boger22,g , O. Bondarenko24 , I. Boyko22 , R. A. Briere4 , H. Cai48 , X. Cai1 , O. Cakir38A ,
A. Calcaterra19A , G. F. Cao1 , S. A. Cetin38B , J. F. Chang1 , G. Chelkov22,b , G. Chen1 , H. S. Chen1 , H. Y. Chen2 ,
J. C. Chen1 , M. L. Chen1 , S. J. Chen28 , X. Chen1 , X. R. Chen25 , Y. B. Chen1 , H. P. Cheng16 , X. K. Chu30 , Y. P. Chu1 ,
G. Cibinetto20A , D. Cronin-Hennessy41 , H. L. Dai1 , J. P. Dai1 , D. Dedovich22 , Z. Y. Deng1 , A. Denig21 , I. Denysenko22 ,
M. Destefanis46A,46C , F. De Mori46A,46C , Y. Ding26 , C. Dong29 , J. Dong1 , L. Y. Dong1 , M. Y. Dong1 , S. X. Du50 ,
P. F. Duan1 , J. Z. Fan37 , J. Fang1 , S. S. Fang1 , X. Fang43 , Y. Fang1 , L. Fava46B,46C , F. Feldbauer21 , G. Felici19A ,
C. Q. Feng43 , E. Fioravanti20A , C. D. Fu1 , Q. Gao1 , Y. Gao37 , I. Garzia20A , K. Goetzen9 , W. X. Gong1 , W. Gradl21 ,
M. Greco46A,46C , M. H. Gu1 , Y. T. Gu11 , Y. H. Guan1 , A. Q. Guo1 , L. B. Guo27 , T. Guo27 , Y. Guo1 , Y. P. Guo21 ,
Z. Haddadi24 , A. Hafner21 , S. Han48 , Y. L. Han1 , F. A. Harris40 , K. L. He1 , Z. Y. He29 , T. Held3 , Y. K. Heng1 , Z. L. Hou1 ,
C. Hu27 , H. M. Hu1 , J. F. Hu46A , T. Hu1 , Y. Hu1 , G. M. Huang5 , G. S. Huang43 , H. P. Huang48 , J. S. Huang14 ,
X. T. Huang32 , Y. Huang28 , T. Hussain45 , Q. Ji1 , Q. P. Ji29 , X. B. Ji1 , X. L. Ji1 , L. L. Jiang1 , L. W. Jiang48 , X. S. Jiang1 ,
J. B. Jiao32 , Z. Jiao16 , D. P. Jin1 , S. Jin1 , T. Johansson47 , A. Julin41 , N. Kalantar-Nayestanaki24 , X. L. Kang1 , X. S. Kang29 ,
M. Kavatsyuk24 , B. C. Ke4 , R. Kliemt13 , B. Kloss21 , O. B. Kolcu38B,c , B. Kopf3 , M. Kornicer40 , W. Kuehn23 , A. Kupsc47 ,
W. Lai1 , J. S. Lange23 , M. Lara18 , P. Larin13 , Cheng Li43 , C. H. Li1 , D. M. Li50 , F. Li1 , G. Li1 , H. B. Li1 , J. C. Li1 , Jin Li31 ,
K. Li12 , K. Li32 , P. R. Li39 , T. Li32 , W. D. Li1 , W. G. Li1 , X. L. Li32 , X. M. Li11 , X. N. Li1 , X. Q. Li29 , Z. B. Li36 ,
H. Liang43 , Y. F. Liang34 , Y. T. Liang23 , G. R. Liao10 , D. X. Lin13 , B. J. Liu1 , C. L. Liu4 , C. X. Liu1 , F. H. Liu33 ,
Fang Liu1 , Feng Liu5 , H. B. Liu11 , H. H. Liu1 , H. H. Liu15 , H. M. Liu1 , J. Liu1 , J. P. Liu48 , J. Y. Liu1 , K. Liu37 , K. Y. Liu26 ,
L. D. Liu30 , Q. Liu39 , S. B. Liu43 , X. Liu25 , X. X. Liu39 , Y. B. Liu29 , Z. A. Liu1 , Zhiqiang Liu1 , Zhiqing Liu21 , H. Loehner24 ,
X. C. Lou1,d , H. J. Lu16 , J. G. Lu1 , R. Q. Lu17 , Y. Lu1 , Y. P. Lu1 , C. L. Luo27 , M. X. Luo49 , T. Luo40 , X. L. Luo1 , M. Lv1 ,
X. R. Lyu39 , F. C. Ma26 , H. L. Ma1 , L. L. Ma32 , Q. M. Ma1 , S. Ma1 , T. Ma1 , X. N. Ma29 , X. Y. Ma1 , F. E. Maas13 ,
M. Maggiora46A,46C , Q. A. Malik45 , Y. J. Mao30 , Z. P. Mao1 , S. Marcello46A,46C , J. G. Messchendorp24 , J. Min1 , T. J. Min1 ,
R. E. Mitchell18 , X. H. Mo1 , Y. J. Mo5 , H. Moeini24 , C. Morales Morales13 , K. Moriya18 , N. Yu. Muchnoi8,a ,
H. Muramatsu41 , Y. Nefedov22 , F. Nerling13 , I. B. Nikolaev8,a , Z. Ning1 , S. Nisar7 , S. L. Niu1 , X. Y. Niu1 , S. L. Olsen31 ,
Q. Ouyang1 , S. Pacetti19B , P. Patteri19A , M. Pelizaeus3 , H. P. Peng43 , K. Peters9 , J. L. Ping27 , R. G. Ping1 , R. Poling41 ,
Y. N. Pu17 , M. Qi28 , S. Qian1 , C. F. Qiao39 , L. Q. Qin32 , N. Qin48 , X. S. Qin1 , Y. Qin30 , Z. H. Qin1 , J. F. Qiu1 ,
K. H. Rashid45 , C. F. Redmer21 , H. L. Ren17 , M. Ripka21 , G. Rong1 , X. D. Ruan11 , V. Santoro20A , A. Sarantsev22,e ,
M. Savri´e20B , K. Schoenning47 , S. Schumann21 , W. Shan30 , M. Shao43 , C. P. Shen2 , P. X. Shen29 , X. Y. Shen1 , H. Y. Sheng1 ,
M. R. Shepherd18 , W. M. Song1 , X. Y. Song1 , S. Sosio46A,46C , S. Spataro46A,46C , B. Spruck23 , G. X. Sun1 , J. F. Sun14 ,
S. S. Sun1 , Y. J. Sun43 , Y. Z. Sun1 , Z. J. Sun1 , Z. T. Sun18 , C. J. Tang34 , X. Tang1 , I. Tapan38C , E. H. Thorndike42 ,
M. Tiemens24 , D. Toth41 , M. Ullrich23 , I. Uman38B , G. S. Varner40 , B. Wang29 , B. L. Wang39 , D. Wang30 , D. Y. Wang30 ,
K. Wang1 , L. L. Wang1 , L. S. Wang1 , M. Wang32 , P. Wang1 , P. L. Wang1 , Q. J. Wang1 , S. G. Wang30 , W. Wang1 , X. F.
Wang37 , Y. D. Wang19A , Y. F. Wang1 , Y. Q. Wang21 , Z. Wang1 , Z. G. Wang1 , Z. H. Wang43 , Z. Y. Wang1 , D. H. Wei10 ,
J. B. Wei30 , P. Weidenkaff21 , S. P. Wen1 , U. Wiedner3 , M. Wolke47 , L. H. Wu1 , Z. Wu1 , L. G. Xia37 , Y. Xia17 , D. Xiao1 ,
Z. J. Xiao27 , Y. G. Xie1 , Q. L. Xiu1 , G. F. Xu1 , L. Xu1 , Q. J. Xu12 , Q. N. Xu39 , X. P. Xu35 , L. Yan43 , W. B. Yan43 ,
W. C. Yan43 , Y. H. Yan17 , H. X. Yang1 , L. Yang48 , Y. Yang5 , Y. X. Yang10 , H. Ye1 , M. Ye1 , M. H. Ye6 , J. H. Yin1 ,
B. X. Yu1 , C. X. Yu29 , H. W. Yu30 , J. S. Yu25 , C. Z. Yuan1 , W. L. Yuan28 , Y. Yuan1 , A. Yuncu38B,f , A. A. Zafar45 ,
A. Zallo19A , Y. Zeng17 , B. X. Zhang1 , B. Y. Zhang1 , C. Zhang28 , C. C. Zhang1 , D. H. Zhang1 , H. H. Zhang36 , H. Y. Zhang1 ,
J. J. Zhang1 , J. L. Zhang1 , J. Q. Zhang1 , J. W. Zhang1 , J. Y. Zhang1 , J. Z. Zhang1 , K. Zhang1 , L. Zhang1 , S. H. Zhang1 ,
X. J. Zhang1 , X. Y. Zhang32 , Y. Zhang1 , Y. H. Zhang1 , Z. H. Zhang5 , Z. P. Zhang43 , Z. Y. Zhang48 , G. Zhao1 , J. W. Zhao1 ,
J. Y. Zhao1 , J. Z. Zhao1 , Lei Zhao43 , Ling Zhao1 , M. G. Zhao29 , Q. Zhao1 , Q. W. Zhao1 , S. J. Zhao50 , T. C. Zhao1 ,
Y. B. Zhao1 , Z. G. Zhao43 , A. Zhemchugov22,g , B. Zheng44 , J. P. Zheng1 , W. J. Zheng32 , Y. H. Zheng39 , B. Zhong27 ,
L. Zhou1 , Li Zhou29 , X. Zhou48 , X. K. Zhou43 , X. R. Zhou43 , X. Y. Zhou1 , K. Zhu1 , K. J. Zhu1 , S. Zhu1 , X. L. Zhu37 ,
Y. C. Zhu43 , Y. S. Zhu1 , Z. A. Zhu1 , J. Zhuang1 , B. S. Zou1 , J. H. Zou1
(BESIII Collaboration)
Institute of High Energy Physics, Beijing 100049, People’s Republic of China
Beihang University, Beijing 100191, People’s Republic of China
Bochum Ruhr-University, D-44780 Bochum, Germany
Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
Central China Normal University, Wuhan 430079, People’s Republic of China
China Center of Advanced Science and Technology, Beijing 100190, People’s Republic of China
COMSATS Institute of Information Technology, Lahore, Defence Road, Off Raiwind Road, 54000 Lahore, Pakistan
G.I. Budker Institute of Nuclear Physics SB RAS (BINP), Novosibirsk 630090, Russia
GSI Helmholtzcentre for Heavy Ion Research GmbH, D-64291 Darmstadt, Germany
Guangxi Normal University, Guilin 541004, People’s Republic of China
GuangXi University, Nanning 530004, People’s Republic of China
Hangzhou Normal University, Hangzhou 310036, People’s Republic of China
Helmholtz Institute Mainz, Johann-Joachim-Becher-Weg 45, D-55099 Mainz, Germany
Henan Normal University, Xinxiang 453007, People’s Republic of China
Typeset by REVTEX
Henan University of Science and Technology, Luoyang 471003, People’s Republic of China
Huangshan College, Huangshan 245000, People’s Republic of China
Hunan University, Changsha 410082, People’s Republic of China
Indiana University, Bloomington, Indiana 47405, USA
(A)INFN Laboratori Nazionali di Frascati, I-00044, Frascati, Italy; (B)INFN and University of Perugia, I-06100, Perugia,
(A)INFN Sezione di Ferrara, I-44122, Ferrara, Italy; (B)University of Ferrara, I-44122, Ferrara, Italy
Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, D-55099 Mainz, Germany
Joint Institute for Nuclear Research, 141980 Dubna, Moscow region, Russia
Justus Liebig University Giessen, II. Physikalisches Institut, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany
KVI-CART, University of Groningen, NL-9747 AA Groningen, The Netherlands
Lanzhou University, Lanzhou 730000, People’s Republic of China
Liaoning University, Shenyang 110036, People’s Republic of China
Nanjing Normal University, Nanjing 210023, People’s Republic of China
Nanjing University, Nanjing 210093, People’s Republic of China
Nankai University, Tianjin 300071, People’s Republic of China
Peking University, Beijing 100871, People’s Republic of China
Seoul National University, Seoul, 151-747 Korea
Shandong University, Jinan 250100, People’s Republic of China
Shanxi University, Taiyuan 030006, People’s Republic of China
Sichuan University, Chengdu 610064, People’s Republic of China
Soochow University, Suzhou 215006, People’s Republic of China
Sun Yat-Sen University, Guangzhou 510275, People’s Republic of China
Tsinghua University, Beijing 100084, People’s Republic of China
(A)Ankara University, Dogol Caddesi, 06100 Tandogan, Ankara, Turkey; (B)Dogus University, 34722 Istanbul, Turkey;
(C)Uludag University, 16059 Bursa, Turkey
University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China
University of Hawaii, Honolulu, Hawaii 96822, USA
University of Minnesota, Minneapolis, Minnesota 55455, USA
University of Rochester, Rochester, New York 14627, USA
University of Science and Technology of China, Hefei 230026, People’s Republic of China
University of South China, Hengyang 421001, People’s Republic of China
University of the Punjab, Lahore-54590, Pakistan
(A)University of Turin, I-10125, Turin, Italy; (B)University of Eastern Piedmont, I-15121, Alessandria, Italy; (C)INFN,
I-10125, Turin, Italy
Uppsala University, Box 516, SE-75120 Uppsala, Sweden
Wuhan University, Wuhan 430072, People’s Republic of China
Zhejiang University, Hangzhou 310027, People’s Republic of China
Zhengzhou University, Zhengzhou 450001, People’s Republic of China
Also at the Novosibirsk State University, Novosibirsk, 630090, Russia
Also at the Moscow Institute of Physics and Technology, Moscow 141700, Russia and at the Functional Electronics
Laboratory, Tomsk State University, Tomsk, 634050, Russia
Currently at Istanbul Arel University, Kucukcekmece, Istanbul, Turkey
Also at University of Texas at Dallas, Richardson, Texas 75083, USA
Also at the PNPI, Gatchina 188300, Russia
Also at Bogazici University, 34342 Istanbul, Turkey
Also at the Moscow Institute of Physics and Technology, Moscow 141700, Russia
Based on data samples collected with the BESIII detector at the BEPCII collider at 9 center-ofmass energies from 4.21 to 4.42 GeV, we search for the production of e+ e− → ωχcJ (J =
√ 0, 1, 2).
The process e+ e− → ωχc0 is observed for the first time, and the Born cross sections at s = 4.23
and 4.26 GeV are measured to be (55.4 ± 6.0 ± 5.9) and (23.7 ± 5.3 ± 3.5) pb, respectively, where
the first uncertainties are statistical and the second are systematic. The ωχc0 signals at the other
7 energies and e+ e− → ωχc1 and ωχc2 signals are not significant, and the upper limits on the cross
sections are determined. By examining the ωχc0 cross section as a function of center-of-mass energy,
we find that it is inconsistent with the line shape of the Y (4260) observed in e+ e− → π + π − J/ψ.
PACS numbers: 14.40.Rt, 13.66.Bc, 14.40.Pq, 13.25.Jx
The charmonium-like state Y (4260) was first ob-
served in its decay to π + π − J/ψ [1], and has small
Is the X(3915) the χc0 (2P )?
Stephen Lars Olsen1
arXiv:1410.6534v1 [hep-ex] 24 Oct 2014
Center for Underground Physics, Institute for Basic Science, Daejeon 305-811, Korea
(Dated: October 27, 2014)
The Particle Data Group has assigned the X(3915) meson, an ωJ/ψ mass peak seen in B →
KωJ/ψ decays and γγ → ωJ/ψ two-photon fusion reactions, as the χc0 (2P ), the 23 P0 charmonium
state. Here it is shown that if the X(3915) is the χc0 (2P ), the measured strength of the γγ →
X(3915) signal implies an upper limit on the branching fraction B(χc0 (2P ) → ωJ/ψ) < 7.8%
that conflicts with a > 14.3% lower limit derived for the same quantity from the B → KX(3915)
¯ 0 in B + → K + D0 D
¯ 0 decays is
decay rate. Also, the absence any signal for X(3915) → D0 D
¯ 0 < 1.2 × B(X(3915) → ωJ/ψ). This contradicts
used to establish the limit B(X(3915) → D0 D
¯ 0 would be a dominant process, while decays to ωJ/ψ,
expectations that χc0 (2P ) decays to D0 D
which are Okubo-Zweig-Iizuka suppressed, would be relatively rare. These, plus reasons given earlier
by Guo and Meissner, raise serious doubts about the X(3915) = χc0 (2P ) assignment.
PACS numbers: 14.40.Pq, 13.25.Gv
values of the mass and width are [7]:
M (X(3915)) = 3918.4 ± 1.9 MeV
A number of meson candidates, dubbed the XY Z
mesons, that contain charmed-quark anticharmed-quark
c) pairs but do not match expectations for any of
the unassigned levels of the c¯
c charmonium spectrum
have been observed in recent experiments. Some have
non-zero electric charge [1] and cannot be accommodated
in the spectrum of charmonium mesons, which are
all electrically neutral. Others are neutral and have
quantum numbers that are accessible by c¯
c systems, but
have properties that fail to match the tightly constrained
expectations of any of the unassigned charmonium
states [2]. To date, there is no compelling theoretical
explanation for these XY Z mesons.
observations of additional states and more refined
measurements of properties of the existing states may
eventually reveal patterns that give clues to their
underlying structure. An important part of this program
is a careful distinction of new states that are conventional
charmonium mesons from those that are not.
The X(3915) was observed by Belle as a near-threshold
peak in the ωJ/ψ invariant mass distribution in exclusive
B → KωJ/ψ decays [3]; it was subsequently confirmed
by BaBar [4]. An ωJ/ψ mass peak with similar mass
and width was reported by Belle in the two-photon
fusion process γγ → ωJ/ψ in 2010 [5].
reported confirmation of the γγ → X(3915) → ωJ/ψ
observation [6] and, from a study of the angular
correlations among the final-state particles, established
the J P C quantum numbers to be 0++ .
The similar masses and widths of the peaks seen in B
decay and in two-photon fusion processes suggest that
these are two different production mechanisms for the
same state. The Particle Data Group’s (PDG) average
Γ(X(3915)) = 20.0 ± 5.0 MeV.
The weighted average of the Belle [3] and BaBar [4]
product branching fraction measurements for X(3915)
production in B decay is
B(B + → K + X(3915)) × B(X(3915) → ωJ/ψ)
= 3.2 ± 0.9 × 10−5 , (2)
while the average of measured production rates in
two-photon fusion (using J P C = 0++ ) gives [7]
X(3915) × B(X(3915) → ωJ/ψ) = 54 ± 9eV,
where Γγγ
X(3915) is the partial width for X(3915) → γγ.
The presence of a J/ψ among its decay products
indicate that the X(3915) contains a c¯
c quark pair. The
only unassigned 0++ charmonium level in the vicinity of
the X(3915) mass is the χc0 (2P ), the first radial exitation
of the χc0 charmonium state. (In the following, the
χc0 (2P ) referred to as the χ′c0 .) Because of this, the PDG
identifies the X(3915) as the χ′c0 . This assignment was
disputed by Guo and Meissner [8], primarily because:
• the partial width for X(3915) → ωJ/ψ is too large
for a decay process that is Okubo-Zweig-Iizuka
(OZI) suppressed for a charmonium state;
¯ decays,
• the lack of evidence for X(3915) → DD
which are expected to be dominant χ′c0 decay
• the small χc2 (2P )-χc0 (2P ) mass splitting.
If the X(3915) is not conventional charmonium but,
instead, another XY Z meson, it would be the lightest
Anisotropic hydrodynamics for conformal Gubser flow
Mohammad Nopoush
Kent State University, Kent OH 44242 USA
Radoslaw Ryblewski
The H. Niewodnicza´
nski Institute of Nuclear Physics,
arXiv:1410.6790v1 [nucl-th] 24 Oct 2014
Polish Academy of Sciences, PL-31342 Krak´ow, Poland
Michael Strickland
Kent State University, Kent OH 44242 USA
We derive the equations of motion for a system undergoing boost-invariant longitudinal and
azimuthally-symmetric transverse “Gubser” flow using leading-order anisotropic hydrodynamics. This is accomplished by assuming that the one-particle distribution function is ellipsoidallysymmetric in the momenta conjugate to the de Sitter coordinates used to parametrize the Gubser
flow. We then demonstrate that the SO(3)q symmetry in de Sitter space further constrains the
anisotropy tensor to be of spheroidal form. The resulting system of two coupled ordinary differential
equations for the de Sitter space momentum scale and anisotropy parameter are solved numerically
and compared to a recently obtained exact solution of the relaxation-time-approximation Boltzmann equation subject to the same flow. We show that anisotropic hydrodynamics describes the
spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches. In addition, we prove that anisotropic hydrodynamics gives the exact solution of
the relaxation-time approximation Boltzmann equation in the ideal, η/s → 0, and free-streaming,
η/s → ∞, limits.
arXiv:1410.6689v1 [astro-ph.HE] 24 Oct 2014
Prepared for submission to JCAP
Antiproton signatures from
astrophysical and dark matter
sources at the galactic center
J. A. R. Cembranosa,b,c V. Gammaldia A. L. Marotoa
a Departamento
de Física Teórica I, Universidad Complutense de Madrid, E-28040 Madrid,
b Facultad
c Dual
de Ciencias, CUICBAS, Universidad de Colima, 28040 Colima, Mexico;
C-P Institute of High Energy Physics, 28040 Colima, Mexico.
E-mail: [email protected], [email protected], [email protected]
Abstract. The center of our Galaxy is a complex region characterized by extreme phenomena. The presence of the supermassive Sagittarius A* black hole, a high Dark Matter (DM)
density and an even higher baryonic density are able to produce very energetic processes.
Indeed, high energetic gamma rays have been observed by different telescopes, although its
origin is not clear. In this work, we constrain the possible antiproton flux component associated to this signal. The expected secondary astrophysical antiproton background already
saturates the observed data. It implies that any other important astrophysical source leads
to an inconsistent excess, since the theoretical uncertainties corresponding to the mentioned
background are small. The constraints depend on the diffusion model and the spectral features of the source. In particular, we consider antiproton spectra described by a power-law,
a monochromatic signal and a Standard Model particle-antiparticle channel production.
A New Look at Those Old Black Holes: Existence of Universal Horizons
Kai Lin
, O. Goldoni
, M.F. da Silva d , and Anzhong Wang
arXiv:1410.6678v1 [gr-qc] 23 Oct 2014
Institute for Advanced Physics & Mathematics,
Zhejiang University of Technology, Hangzhou 310032, China
Instituto de F´ısica, Universidade de S˜
ao Paulo, CP 66318, 05315-970, S˜
ao Paulo, Brazil
Departamento de F´ısica Te´
orica, Universidade do Estado do Rio de Janeiro,
Rua S˜
ao Francisco Xavier 524, Maracan˜
a, CEP 20550013, Rio de Janeiro, RJ, Brazil
GCAP-CASPER, Physics Department, Baylor University, Waco, TX 76798-7316, USA
(Dated: October 27, 2014)
In this paper, we study the existence of universal horizons in static spacetimes, and find that
the khronon field can be solved explicitly when its velocity becomes infinitely large, in which the
universal horizons coincide with the sound horizon of the khronon. Choosing the timelike coordinate
aligned with the khronon, the static metric takes a simple form, from which it can be seen clearly
that the metric now is free of singularity at the Killing horizons, but becomes singular at the
universal horizons. Applying such developed formulas to three well-known black hole solutions,
the Schwarzschild, Schwarzschild anti-de Sitter, and Reissner-Nordstr¨
om, we find that in all these
solutions universal horizons exist and are always inside the Killing horizons. The peeling-off behavior
of the khronon depends on the coordinates adopted. In particular, in the Schwarzschild coordinates
the khronon is peeling off at both Killing and universal horizons, while in the Eddington-Finkelstein
and Painleve-Gullstrand coordinates, the peeling-off behavior is found only when across the universal
horizons. We also calculate the surface gravity at each of the universal horizons, and find that the
surface gravity at the universal horizon is always greeter than that at the Killing horizon.
PACS numbers: 04.60.-m; 98.80.Cq; 98.80.-k; 98.80.Bp
hypersurface-orthogonal and timelike vector field uµ ,
u[ν Dα uβ] = 0.
The studies of black holes have been one of the main
objects both theoretically and observationally over the
last half of century [1, 2], and so far there are many
solid observational evidences for their existence in our
universe. Theoretically, such investigations have been
playing a crucial role in the understanding of the nature
of gravity in general, and quantum gravity in particular.
They started with the discovery of the laws of black hole
mechanics [3] and Hawking radiation [4], and led to the
profound recognition of the thermodynamic interpretation of the four laws [5] and the reconstruction of general
relativity (GR) as the thermodynamic limit of a more
fundamental theory of gravity [6]. More recently, they
are essential in understanding the AdS/CFT correspondence [7, 8] and firewalls [9].
Lately, such studies have gained further momenta
in the framework of gravitational theories with broken
Lorentz invariance (LI) [10–13]. In particular, Blas and
Sibiryakov showed that an absolute horizon exists with
respect to any signal with any large velocity, including
the one with infinitely large one (instantaneous propagation) [10]. Such a horizon is dubbed as the universal
horizon, which is always located inside a Killing horizon.
A critical point is the existence of a globally well-defined
∗ The
corresponding author
E-mail: Anzhong [email protected]
Then, it implies that there exists a scalar field φ [14], so
uµ = √ ,
where φ,µ ≡ ∂φ/∂xµ , X ≡ −g αβ ∂α φ∂β φ. Clearly, uµ is
invariant under the gauge transformations,
φ˜ = F(φ),
where F(φ) is a monotonically increasing and otherwise
arbitrary function of φ. Such a scalar field was often
referred to as the khronon [15], and is equivalent to the
Einstein-aether (Æ-) theory [16], when the aether uµ is
hypersurface-orthogonal, as showed explicitly in [17] (See
also [18]).
Note that in the studies of the existence of the universal horizons carried out so far [10–13], the khronon
field is always part of the underlined theory of gravity.
To generalize such definitions to any theories that violate LI, recently the khronon φ was promoted to a probe
field, and assumed that it plays the same role as a Killing
vector field in a given space-time, so its existence does
not affect the background, but defines the properties of
it [19]. By this way, such a field is no longer part of
the gravitational field and it may or may not exist in a
given space-time. Applied such a generalized definition
of the universal horizons to static charged solutions of
the healthy extensions [15] of the Hoˇrava-Lifshitz (HL)
Magnetic field instability in a neutron star driven by electroweak electron-nucleon
interaction versus chiral magnetic effect
arXiv:1410.6676v1 [astro-ph.HE] 24 Oct 2014
Maxim Dvornikova,b and Victor B. Semikozb
Institute of Physics, University of S˜
ao Paulo, CP 66318,
CEP 05315-970 S˜
ao Paulo, SP, Brazil;
Pushkov Institute of Terrestrial Magnetism,
Ionosphere and Radiowave Propagation (IZMIRAN),
142190 Troitsk, Moscow, Russia
(Dated: October 27, 2014)
We show that the Standard Model electroweak interaction of ultrarelativistic electrons with nucleons (eN interaction) in a neutron star (NS) permeated by a seed large-scale helical magnetic field
provides its growth up to & 1015 G during a time comparable with the ages of young magnetars
∼ 104 yr. The magnetic field instability originates from the parity violation in the eN interaction
entering the generalized Dirac equation for right and left massless electrons in an external uniform
magnetic field. The averaged electric current given by the solution of the modified Dirac equation
contains an extra current for right and left electrons (positrons). Such current includes both a
changing chiral imbalance of electrons and the eN potential given by a constant neutron density in
NS. Then we derive the system of the kinetic equations for the chiral imbalance and the magnetic
helicity which accounts for the eN interaction. By solving this system, we show that a sizable chiral
imbalance arising in a neutron protostar due to the Urca-process e−
L + p → N + νeL diminishes very
rapidly because of a huge chirality flip rate. Thus the eN term prevails the chiral effect providing
a huge growth of the magnetic helicity and the helical magnetic field.
PACS numbers: 97.60.Jd, 11.15.Yc, 25.30.Bf
Some neutron stars (NSs), called magnetars, having
magnetic fields B ∼ 1015 − 1016 G, can be considered
as strongest magnets in our universe [1]. Despite the
existence of various models for the generation of such
strong fields, based, e.g., on the turbulent dynamo [2],
the origin of magnetic fields in magnetars is still an open
problem. Recently, in Ref. [3] the authors tried to apply
the chiral magnetic effect [4, 5], adapted successfully for
the QED plasma [6], to tackle the problem of magnetic
fields in magnetars. The approach of Ref. [3] implies the
chiral kinetic theory, where Vlasov equation is modified
when adding the Berry curvature term to the Lorentz
force [7].
The fate of such a chiral plasma instability is based
on the Adler anomaly in QED with the nonconservation of the pseudovector current for massless fermions
¯ µ γ5 ψ in external electromagnetic fields. Since this
current is the difference of right jµR and left jµL currents, the assumption of a seed imbalance between their
densities given by the difference of chemical potentials,
(nR − nL ) ∼ µ5 = (µR − µL )/2 6= 0, where nR,L are the
densities of right and left fermions (electrons) and µR,L
are their chemical potentials, could lead to the magnetic
field instability we study here adding electroweak interactions in the Standard Model (SM).
The same effect (while without weak interactions) was
used in Ref. [8] to study the self-consistent evolution of
the magnetic helicity in the hot plasma of the early Universe driven by the change of the lepton asymmetry ∼ µ5 .
In Ref. [8] it was showed that such an asymmetry diminishes, µ5 → 0, due to the growth of the chirality flip rate
in the cooling universe through electron-electron (ee) col2
lisions, Γf ∼ α2em m
≈ 137
is the
, where αem = 4π
fine structure constant, me is the electron mass, and T
is the plasma temperature.
This negative result encouraged the appearance of
Ref. [9], where another mechanism for the generation of
magnetic fields was proposed. It is based on the parity
violation in electroweak plasma resulting in the nonzero
Chern-Simons (CS) term Π2 that enters the antisymmetric part of the photon polarization operator in plasma of
massless particles. Here we adopt the notation for the
CS term from Ref. [9]. In Ref. [10], a similar CS term
Π2 , based on the neutrino interactions with charged
leptons, was calculated. Basing on this calculation, the
magnetic field instability driven by neutrino asymmetries
was revealed. This instability is implemented in different
media such as the hot plasma of the early universe and
a supernova (SN) with a seed magnetic field.
The amplification of a seed magnetic field during the
SN burst driven by a non-zero electron neutrino asym(νe)
metry ∆nνe 6= 0 which enters the CS term Π2 was suggested in Ref. [10] to explain the generation of strongest
magnetic fields in magnetars. Note that after the SN
burst a cooling NS as the corresponding SN remnant
emits equally neutrinos and antineutrinos. Thus, the
neutrino asymmetry vanishes. The inclusion of the electroweak ee-interaction with a stable fraction of degenerate electrons ne ≈ const instead of the νe interaction
with vanishing neutrino asymmetry ∆nνe → 0 has no
sense since the corresponding parity violating CS term
Π2 tends to zero in the static limit ω → 0 for an elec-
Spontaneous supersymmetry breaking in the 2d N = 1 Wess-Zumino model
Kyle Steinhauer and Urs Wenger∗
Albert Einstein Center for Fundamental Physics,
University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland.
(Dated: October 27, 2014)
We study the phase diagram of the two-dimensional N = 1 Wess-Zumino model on the lattice
using Wilson fermions and the fermion loop formulation. We give a complete nonperturbative
determination of the ground state structure in the continuum and infinite volume limit. We also
present a determination of the particle spectrum in the supersymmetric phase, in the supersymmetry
broken phase and across the supersymmetry breaking phase transition. In the supersymmetry
broken phase we observe the emergence of the Goldstino particle.
arXiv:1410.6665v1 [hep-lat] 24 Oct 2014
PACS numbers: 11.30.Pb,11.30.Qc,12.60.Jv,05.50.+q
Understanding the spontaneous breakdown of supersymmetry is a generic nonperturbative problem which
is relevant not only for particle physics but in fact for
many physical systems beyond quantum field theories.
The N = 1 Wess-Zumino model [1, 2] in two dimensions is one of the simplest supersymmetric quantum
field theories which allows for spontaneous supersymmetry breaking since it enjoys the necessary but not sufficient condition of a vanishing Witten index [3]. The
model has been analysed employing various approaches
such as Monte Carlo methods [4, 5], Hamiltonian techniques [6–8], or exact renormalisation group methods [9].
Wilson derivatives for fermions and bosons, guaranteeing a supersymmetric continuum limit [10], were used in
[11] and a numerical analysis of the phase diagram using the SLAC derivative has been conducted in [12]. All
approaches use various regulators which are more or less
difficult to control. In this letter we report on our results
for the two-dimensional N = 1 Wess-Zumino model regularized on a Euclidean spacetime lattice. The discretization using Wilson derivatives for the fermions and bosons
[10] together with the fermion loop formulation and a
novel algorithm [13] allows to systematically remove all
effects from the IR and UV regulators by explicitly taking the necessary limits in a completely controlled way.
One reason why this has not been achieved so far with
other methods is the fact that all supersymmetric systems with spontaneously broken supersymmetry suffer
from a fermion sign problem related to the vanishing of
the Witten index [14]. However, that sign problem can be
circumvented in our approach by using the exact reformulation of the lattice model in terms of fermion loops [14].
In this formulation the partition function is obtained as
a sum over closed fermion loop configurations and separates naturally into its bosonic and fermionic parts for
which the sign is perfectly under control. Efficient simulations with an open fermion string (or fermionic worm)
algorithm [13] are then possible even in the phase with
spontaneously broken supersymmetry where the massless
Goldstino mode is present.
The two-dimensional N = 1 Wess-Zumino model [1, 2]
contains a real two component Majorana spinor ψ and a
real bosonic field φ and is described in Euclidean spacetime by the on-shell continuum action
(∂µ φ)2 + ψDψ +
S = d2 x
where D = ∂/ + P 00 (φ) is the Majorana Dirac operator. Here, P (φ) denotes a generic superpotential and P 0
and P 00 its first and second derivative with respect to φ,
respectively. The action is invariant under a supersymmetry transformation δ which transforms φ, ψ and ψ as
δφ = ψ,
/ − P 0 ),
δψ = (∂φ
δψ = 0,
where is a constant Majorana spinor. In the following
we will concentrate on the specific superpotential
P (φ) =
1 3 m2
gφ −
With this potential, the action is also invariant under a
discrete Z2 /chiral symmetry transformation
φ → −φ,
ψ → σ3 ψ,
ψ → −ψσ3
which in the following we denote by Zχ2 symmetry. The
potential yields a vanishing Witten index W = 0 and
hence allows for spontaneous supersymmetry breaking
[3]. This can for example be derived from the transformation properties of the Pfaffian Pf(D) under the Z2
symmetry φ → −φ [15].
When the model is regularized on a discrete spacetime
lattice both the Zχ2 and the supersymmetry are broken
explicitly, but the discretization can be chosen such that
the restoration of the symmetries is guaranteed in the
continuum limit [10]. This can be achieved because the
model is superrenormalisable and only one counterterm
is necessary to renormalize the bare mass m, while the
coupling g is not renormalized and can hence be used to
define the continuum limit ag → 0 where a is the lattice
Prospects of determination of reheating temperature after inflation by DECIGO
arXiv:1410.6618v1 [astro-ph.CO] 24 Oct 2014
Sachiko Kuroyanagi1, Kazunori Nakayama2, and Jun’ichi Yokoyama3,4
Department of Physics,
Tokyo University of Science, Kagrazaka, Japan
Department of Physics, Graduate School of Science,
The University of Tokyo, Tokyo 113-0033, Japan
Research Center for the Early Universe (RESCEU),
Graduate School of Science,
The University of Tokyo, Tokyo 113-0033, Japan
Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU),
WPI, TODIAS, The University of Tokyo, Kashiwa, Japan
(Dated: October 27, 2014)
If the tensor-to-scalar ratio r of cosmological perturbations takes a large value r ∼ 0.1, which
may be inferred by recent BICEP2 result, we can hope to determine thermal history, in particular,
the reheating temperature, TR , after inflation by space-based laser interferometers. It is shown
that upgraded and upshifted versions of DECIGO may be able to determine TR if it lies in the
range 6 × 106 < TR < 5 × 107 GeV and 3 × 107 < TR < 2 × 108 GeV, respectively. Although these
ranges include predictions of some currently plausible inflation models, since each specification can
probe TR of at most a decade range, we should determine the specifications of DECIGO with full
account of constraints on inflation models to be obtained by near-future observations of temperature
anisotropy and B-model polarization of the cosmic microwave background radiation.
After more than three decades from its original proposal [1, 2], the inflationary cosmology is now confronting and
passing a number of observational tests. Among its generic predictions, the spatial flatness and generation of almost
scale-invariant spectrum of curvature perturbations [3] were first confirmed by precise measurements of the cosmic
microwave background radiation (CMB) by WMAP [4, 5] and are now being updated by Planck [6, 7]. The Gaussian
nature of these fluctuations has also been further confirmed recently by Planck [8].
In March 2014, the BICEP2 collaboration [9] reported detection of the B-mode polarization of CMB over a fairly
wide range of angular multipoles from ℓ ≃ 40 to 350. The higher multipole range can be explained by gravitational
lensing while the smaller multipoles are interpreted as owing to the long-wave gravitational waves of primordial origin,
most likely from the tensor perturbations generated quantum mechanically during inflationary expansion stage in the
early Universe [10]. If what they measured had not been contaminated by foregrounds, it would correspond to the
amplitude of the tensor-to-scalar ratio as r = 0.20+0.07
−0.05 [9]. Note that r is related with the energy scale of inflation as
V = (3.2 × 1016 GeV)4 r.
This value, on the other hand, is larger than that expected by the constraints imposed by WMAP [5] and Planck
[7] in terms of temperature anisotropy and E-mode polarization, because they reported 95% upper bounds on r as
r < 0.13 and 0.11, respectively, and that the likelihood contours in (ns , r) plane preferred the tensor-to-scalar ratio
significantly smaller than 0.1. As a result, models predicting tiny values of r such as r ∼ 10−3 had been investigated
extensively including the curvature square inflation [2] and the original Higgs inflation model [11], which occupy the
central region of the likelihood contours. These models would be ruled out if large tensor perturbation would be
observationally established 1 .
After the original announcement of BICEP2, several analyses of the effects of dust contamination have been done,
and it has been pointed out that they may be so large that the observed B-mode polarization may be entirely due to
the dust foreground [15] and we only have an upper bound on r.
In any event, the BICEP2 observation has reminded us the lesson that the truth may not lie in the center of the
likelihood contour and we should remain open-minded until the final result is established. Hence here we consider the
case with r close to its observational upper bound r ∼ 0.1. The most plausible feature of a relatively large value of r
is that direct observation of tensor perturbations becomes more feasible by future space-based laser interferometers
such as DECIGO [16], which also allow us to extract useful information on the thermal history after inflation [17]. For
example, information on reheating is imprinted in the gravitational wave spectrum in the frequencies corresponding
to the energy scale of reheating. Thus, the targeting frequency of the experiment is a key for determining reheating
temperature and would be better to be adjusted once we obtain a hint about reheating from either cosmology or
Even in such a case the Higgs field in the Standard Model could be an inflaton, because newer Higgs inflation models such as Higgs
G-inflation [12] or running kinetic inflation [13] could work well to accommodate large enough r as summarized in [14].
Absolute measurement of thermal noise in a resonant short-range force experiment
Absolute measurement of thermal noise in a resonant shortrange force experiment
H Yan1, E A Housworth2, H O Meyer1, G Visser3, E Weisman1, and J C Long1,4
Department of Physics, Indiana University, Bloomington, Indiana 47405, USA
Department of Mathematics, Indiana University, Bloomington, Indiana 47405, USA
Center for Exploration of Energy and Matter, Indiana University, Bloomington, Indiana 47408, USA
(Submitted 12 May 2014; revised 5 August 2014)
Planar, double-torsional oscillators are especially suitable for short-range macroscopic force search
experiments, since they can be operated at the limit of instrumental thermal noise. As a study of this limit, we
report a measurement of the noise kinetic energy of a polycrystalline tungsten oscillator in thermal equilibrium
at room temperature. The fluctuations of the oscillator in a high-Q torsional mode with a resonance frequency
near 1 kHz are detected with capacitive transducers coupled to a sensitive differential amplifier. The electronic
processing is calibrated by means of a known electrostatic force and input from a finite-element model. The
measured average kinetic energy, Eexp = (2.0 ± 0.3)·10−21 J, is in agreement with the expected value of
k BT .
PACS numbers: 46.80.+j, 05.40.-a, 04.80.Cc, 07.07.Df, 07.10.Fq
The equipartition theorem predicts that any physical system in thermal equilibrium is associated with
energy. In particular, this holds for mechanical systems used in precision force measurements, where the
random thermal motion of the detector represents one of the dominant noise sources and may limit the
sensitivity that can be achieved [1].
In the experiment reported here, we investigate thermal noise by carrying out a measurement of the
random kinetic energy Eexp of a torsional thin-plate detector. In contrast to a previous study of thermal
noise in a single-crystal silicon oscillator of similar shape [2], we take a somewhat different approach in
which a calibration procedure and a finite-element model are used to produce an absolute measurement of
Eexp which can be compared directly to the prediction of the equipartition theorem.
Author to whom correspondence should be addressed: [email protected]
Lepton-Flavored Scalar Dark Matter with Minimal Flavor Violation
arXiv:1410.6803v1 [hep-ph] 24 Oct 2014
Chao-Jung Lee and Jusak Tandean
Department of Physics and Center for Theoretical Sciences,
National Taiwan University,
Taipei 106, Taiwan
We explore scalar dark matter (DM) that is part of a lepton flavor triplet satisfying symmetry requirements under the hypothesis of minimal flavor violation. The theory contains in addition three right-handed
neutrinos that participate in the seesaw mechanism for neutrino mass generation. The stability of the DM
is tied to the choice of lepton flavor quantum numbers for the triplet, and its interactions with standard
model (SM) particles have minimal flavor violation built-in. The DM couples to SM particles via Higgsportal renormalizable interactions as well as to leptons through dimension-six operators. We consider
restrictions on the new scalars from the Higgs boson measurements, observed relic density, DM direct
detection experiments, and searches for flavor-violating lepton decays. The viable parameter space can be
tested further with future data. Also, we investigate the possibility of the scalar couplings accounting for
the tentative hint of Higgs flavor-violating decay h → µτ recently detected in the CMS experiment. They
are allowed by constraints from other Higgs data to produce a rate of this decay roughly compatible with
the CMS finding.
LTH 1025
arXiv:1410.6715v1 [hep-ph] 24 Oct 2014
Momentum subtraction and the R-ratio
J.A. Gracey,
Theoretical Physics Division,
Department of Mathematical Sciences,
University of Liverpool,
P.O. Box 147,
L69 3BX,
United Kingdom.
Abstract. We determine the R-ratio for massless quarks in several renormalization schemes to
various loop orders. These are the momentum subtraction schemes of Celmaster and Gonsalves
as well as the minimal momentum subtraction scheme. The dependence of the R-ratio on the
schemes is analysed.
QCD Phenomenology
arXiv:1410.6686v1 [hep-ph] 24 Oct 2014
Roger José Hernández-Pinto
Departamento de Física, FCEyN, Universidad de Buenos Aires,
(1428) Pabellón 1 Ciudad Universitaria, Capital Federal, Argentina and
Instituto de Física Corpuscular, Universitat de València - Consejo Superior de Investigaciones
Científicas, Parc Científic, E-46980 Paterna, Valencia, Spain
Abstract. Quantum Chromodynamics is the most successful theory in particle physics. The understanding of
all different signals at hadron colliders have been achieved due to the correct interpretation of the theory. In
this paper we review some basic features of the theory of strong interactions and how it could be used in order
to provide phenomenological distributions for the Large Hadron Collider. The main results presented in here
can be found in Ref [1].
Keywords: <Quantum Chromodynamics, Perturbative calculations, Standard-model Higgs bosons>
PACS: <12.38.-t, 12.38.Bx, 14.80.Bn>
The Large Hadron Collider (LHC) is the biggest machine ever built by humanity. Its main
purpose, the discovery of the last remaining particle of the Standard Model (SM) was achieved
in 2012. Theorists and experimentalists from all around the globe made an enormous effort
in order to succeed on this task. Experiments are achieving a very high precision in all
measurements, and they are now also pushing theorists to provide phenomenological SM
predictions at the same level of accuracy. Besides that, the new era of the LHC is coming, and
the disentanglement of the properties of the Higgs particle or the discovery of new physics,
require theoretical Monte Carlo simulations, of signal and background, at the highest possible
The SM of particle physics is based on a gauge theory of SU(3)c × SU(2)L × U(1)Y and
it has been by far the most precise theory of nature. In particular, the sector of the theory
which governs the physics of the LHC is the one related with the SU(3)c. The LHC collides
protons at center of mass energies of the order of TeVs. Protons are made of quarks and
gluons, elementary particles of the SM. The description of these partons is well understood in
the framework of Quantum Chromodynamics (QCD). Unfortunately, QCD cannot be solved
completely, and usually in order to make theoretical predictions for hadron colliders, one takes
the perturbative version of QCD (pQCD). In the perturbative regime, the coupling associated
to SU(3)c is considered small and the series expansion is allowed. However, at the LHC, this
assumption is only valid just in the moment when the collision occurs and when particles are
flowing into detectors this statement could not be longer true. In order to compute observables,
it is important to know how to include the perturbative part and the non perturbative one in the
calculation. In fact, one way to describe the production of a hadron H at the LHC is a mixing
arXiv:1410.6684v1 [hep-ph] 24 Oct 2014
EPJ Web of Conferences will be set by the publisher
DOI: will be set by the publisher
c Owned by the authors, published by EDP Sciences, 2014
Decay Constants of Beauty Mesons from QCD Sum Rules
Wolfgang Lucha1 , a , Dmitri Melikhov2,3, b , and Silvano Simula4, c
Institute for High Energy Physics, Austrian Academy of Sciences, Nikolsdorfergasse 18, A-1050 Vienna,
Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria
D. V. Skobeltsyn Institute of Nuclear Physics, M. V. Lomonosov Moscow State University, 119991, Moscow,
INFN, Sezione di Roma Tre, Via della Vasca Navale 84, I-00146, Roma, Italy
Abstract. Our recently completed analysis of the decay constants of both pseudoscalar
and vector beauty mesons reveals that in the bottom-quark sector two specific features of
the sum-rule predictions show up: (i) For the input value of the bottom-quark mass in the
MS scheme mb (mb ) ≈ 4.18 GeV, the sum-rule result fB ≈ 210–220 MeV for the B meson
decay constant is substantially larger than the recent lattice-QCD finding fB ≈ 190 MeV.
Requiring QCD sum rules to reproduce the lattice-QCD value of fB yields a significantly
larger b-quark mass: mb (mb ) = 4.247 GeV. (ii) Whereas QCD sum-rule predictions for
the charmed-meson decay constants fD , fDs , fD∗ and fD∗s are practically independent of the
choice of renormalization scale, in the beauty sector the results for the decay constants—
and especially for the ratio fB∗ / fB —prove to be very sensitive to the specific scale setting.
1 Correlator, operator product expansion, and heavy-quark mass schemes
The starting point of our QCD sum-rule evaluation of the decay constants [1] of beauty mesons is the
time-ordered product of two meson interpolating currents, viz., j5 (x) = (mb +m) q(x)
¯ i γ5 b(x) for the B
meson and jµ (x) = q(x)
¯ γµ b(x) for the B∗ meson. The correlator of pseudoscalar currents is defined by
Π(p ) ≡ i d4 x ei p x 0 T j5 (x) j†5 (0) 0 .
The Borel transform of this correlation function depends on some Borel parameter τ and takes the form
Π(τ) =
exp −MB2 τ +
(MB∗ +MP )2
ds e
−s τ
ρhadr (s) =
ds e−s τ ρpert (s, µ) + Πpower (τ, µ) .
(mb +m)2
The B-meson decay constant fB is defined by h0| j5 (0)|Bi = fB MB2 . In order to remove all excited-state
contributions, we adopt the standard assumption of quark–hadron duality: the contributions of excited
a e-mail: [email protected]
b e-mail: [email protected]
c e-mail: [email protected]
arXiv:1410.6682v1 [hep-ph] 24 Oct 2014
SQUID-based Resonant Detection
of Axion Dark Matter
Vladimir A. Popov
Institute of Physics, Kazan Federal University,
Kremlyovskaya st. 18, Kazan 420008, Russia
A new method for searching for Dark Matter axions is proposed.
It is shown that a two-contact SQUID can detect oscillating magnetic
perturbations induced by the axions in a strong inhomogeneous magnetic field. A resonant signal is a steplike response in the SQUID
current-voltage characteristic at a voltage corresponding to the axion
mass with a height depending on the axion energy density near the
Earth. The proposed experimental technique appears to be sensitive
to the axions with masses ma . 10−4 eV, which is well-motivated by
current researches both in cosmology and in particle physics.
To understand the nature of the Dark Matter (DM) is among major
challenges in the present-day cosmology. A number of particles is considered
as DM candidates (WIMPs, sterile neutrinos, ets.) and low mass axions
are highly attractive ones. The experimental discovery of the axions would
give new insights into cosmological and astrophysical researches as well as
into particle physics since the axions play a central role in the solution to
the strong CP -problem. This provides that experimental searching for the
axions with mass in the range of 10−6 − 10−3 eV is of paramount importance.
The experimental techniques [1, 2, 3, 4] for DM axions detection are
based on axion-phonon conversation processes. Their theoretical description
Nuclear Physics B
Nuclear Physics B Proceedings Supplement 00 (2014) 1–5
New method for precise determination of top quark mass at LHC
Sayaka Kawabata
arXiv:1410.6654v1 [hep-ph] 24 Oct 2014
Department of Physics, Tohoku University, Sendai 980-8578, Japan
A new method to measure the mass of the top quark at the LHC is presented [1]. This method uses lepton energy
distribution and ideally does not depend on the velocity distribution of the top quark. We perform a simulation
analysis of the top quark mass reconstruction using this method at the leading order, taking account of experimental
circumstances. We estimate the sensitivity of the mass determination. The results show that this method is viable
in realistic experimental conditions and has a possibility to achieve a good accuracy in determining a theoretically
well-defined top quark mass by including higher-order corrections.
Keywords: top quark, top quark mass, measurement, LHC, QCD
1. Introduction
The mass of the top quark is an important input parameter to various physics. In the electroweak precision
tests, the top quark mass gives a large contribution to
radiative corrections, and accordingly, its precise value
is desired in order to scrutinize possible deviations from
the Standard Model (SM) [2, 3]. Furthermore, the stability of the SM vacuum up to the Planck scale depends
crucially on the value of the top quark mass [4, 5]. Now
that the Higgs boson has been discovered [6, 7] and the
SM is getting more established, a demand for precise
measurements of the top quark mass is increasing.
The top quark mass has been measured at the LHC
and Tevatron, and their recent combined result yields [8]
mt = 173.34 ± 0.27(stat) ± 0.71(syst) GeV .
It achieves 0.4% precision, and more accurate results
are expected to be obtained in future analyses [9].
This mass, however, is not identical to the pole mass
nor well-defined in perturbative QCD. Since the above
measurements utilize Monte Carlo (MC) simulations
and reconstruct the mass from final-state momenta including jet momenta, the measured mass depends on
the hadronization models in the MCs, which we cannot
treat within perturbative QCD [10]. Thus, the definition
of the measured mass in perturbative theory is ambiguous, and even its relation to the pole or MS mass is not
known [11].
Some alternative methods have been proposed and
developed to complement the above measurements with
different systematic uncertainties or extract a theoretically well-defined top quark mass [12, 13, 14, 15, 16,
17, 18, 19, 20, 21, 22]. However, so far, no method
has achieved to obtain a theoretically well-defined mass
with high precision.
In this paper, we present a new method to measure the
top quark mass at the LHC. This method has characteristics of using lepton distributions and basically being
independent of the kinematics of the production process
of top quarks. Consequently, it does not suffer from the
ambiguity of hadronization models. Using this method,
we can determine the pole mass and MS mass of the top
In Sec. 2, a basis of our method, named the “weight
function method”, is presented. We perform a simulation analysis of the top quark mass reconstruction using
it and the results are shown in Sec. 3. Section 4 is devoted to conclusions.
More details of the analysis and discussions in this
paper are given in Ref. [1].
arXiv:1410.6624v1 [hep-ph] 24 Oct 2014
Unification of Coupling Constants, Dimension six
Operators and the Spectral Action
Agostino Devastato1,2 , Fedele Lizzi1,2,3 , Carlos Valc´arcel Flores4 and Dmitri Vassilevich4
Dipartimento di Fisica, Universit`a di Napoli Federico II
INFN, Sezione di Napoli
Monte S. Angelo, Via Cintia, 80126 Napoli, Italy
Departament de Estructura i Constituents de la Mat`eria,
Institut de Ci`encies del Cosmos, Universitat de Barcelona,
Barcelona, Catalonia, Spain
CMCC-Universidade Federal do ABC, Santo Andr`e, S.P., Brazil
[email protected], [email protected], [email protected],
[email protected]
We investigate whether inclusion of dimension six terms in the Standard Model lagrangean may cause the unification of the coupling constants at a scale comprised between 1014 and 1017 GeV. Particular choice of the dimension 6 couplings is motivated by
the spectral action. Given the theoretical and phenomenological constraints, as well as
recent data on the Higgs mass, we find that the unification is indeed possible, with a lower
unification scale slightly favoured.
Nuclear Physics B
Nuclear Physics B Proceedings Supplement 00 (2014) 1–6
On the smallness of the cosmological constant
C. D. Froggatta , R. Nevzorovb,c , H. B. Nielsend , A. W. Thomasb
a School
of Physics and Astronomy, University of Glasgow, Glasgow, UK
Centre of Excellence for Particle Physics at the Tera–scale,
School of Chemistry and Physics, University of Adelaide, Adelaide SA 5005, Australia
c Institute for Theoretical and Experimental Physics, Moscow, 117218, Russia
d The Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
arXiv:1410.6620v1 [hep-ph] 24 Oct 2014
In N = 1 supergravity the scalar potential of the hidden sector may have degenerate supersymmetric (SUSY) and
non-supersymmetric Minkowski vacua. In this case local SUSY in the second supersymmetric Minkowski phase can
be broken dynamically. Assuming that such a second phase and the phase associated with the physical vacuum are
exactly degenerate, we estimate the value of the cosmological constant. We argue that the observed value of the dark
energy density can be reproduced if in the second vacuum local SUSY breaking is induced by gaugino condensation
at a scale which is just slightly lower than ΛQCD in the physical vacuum. The presence of a third degenerate vacuum,
in which local SUSY and electroweak (EW) symmetry are broken near the Planck scale, may lead to small values of
the quartic Higgs self–coupling and the corresponding beta function at the Planck scale in the phase in which we live.
Keywords: Supergravity, Cosmological constant, Higgs boson
PACS: 04.65.+e, 98.80.Es, 14.80.Bn
1. Introduction
It is commonly expected that the exploration of TeV
scale physics at the LHC may lead to the discovery of
new physics phenomena beyond the Standard Model
(SM) that can shed light on the stabilisation of the EW
scale. Indeed, if the SM is embedded in a more fundamental theory characterized by a much larger energy
scale (e.g. the Planck scale MPl ≈ 1019 GeV) than the
EW scale, then due to the quadratically divergent radiative corrections, the Higgs boson tends to acquire a mass
of the order of the larger energy scale; excessive finetuning is then required to keep the Higgs mass around
the observed value ∼ 125 GeV.
Despite the compelling arguments for physics beyond
the SM, no signal or indication of its presence has been
detected at the LHC so far. Besides there are some reasons to believe that the SM is extremely fine-tuned. Indeed, astrophysical and cosmological observations indicate that there is a dark energy spread all over the
Universe which constitutes 70% − 73% of its energy
density. A fit to the recent data shows that its value
is ρΛ ∼ 10−123 MPl
∼ 10−55 MZ4 [1, 2]. At the same
time much larger contributions should come from elec4
troweak symmetry breaking (∼ 10−67 MPl
) and QCD
−79 4
condensates (∼ 10 MPl ). The contribution of zero–
modes is expected to push the vacuum energy density
even higher up to ∼ MPl
, i.e.
ρΛ '
X ωb
X ωf
f ermions
Ω "X
|~k|2 + m2b −
# 3
d ~k
|k| + m f
∼ −Ω4 ,
where the mb and m f are the masses of bosons and
fermions while Ω ∼ MPl . Because of the cancellation
needed between the contributions of different condensates to ρΛ , the smallness of the cosmological constant
should be regarded as a fine–tuning problem.
The effect of uu diquark suppression in proton splitting in
Monte Carlo event generators
V. Uzhinsky1,2 , A. Galoyan3
Monte Carlo event generators assume that protons split into (uu)-diquarks and d-quarks
with a probability of 1/3 in strong interactions. It is shown in this paper that using a
value of 1/6 for the probability allows one to describe at a semi-quantitative level the NA49
Collaboration data for p + p → p + X reactions at 158 GeV/c. The Fritiof (FTF) model
of Geant4 was used to simulate the reactions. The reduced weight of the (uu)-diquarks in
protons is expected in the instanton model.
Most of the Monte Carlo event generators of multi-particle production assume that nucleons split
into diquarks and quarks in strong interactions. In particular, protons split into (ud)-diquarks and uquarks with a probability of 2/3, and into (uu)-diquarks and d-quarks with a probability of 1/3. At the
same time, there are various physical signatures that the probabilities can be different [1]. For example,
it was assumed in the papers [2], as in many other papers, that the (ud)–u configuration completely
dominates in the proton wave function. This was motivated be the instanton model [3] of the QCD
vacuum. According to that model, quark-quark interactions are flavor-dependent: they are non-zero only
if quarks have different flavors. Thus, (uu)-diquarks must be suppressed in protons [4]. The true weight
of the (uu)–d configuration can be estimated using the NA49 Collaboration data [5].
The NA49 Collaboration presented high precision data on particle production in pp interactions at
158 GeV/c including xF , pT and rapidity distributions of various particles (p, n, π ± , K ± , p¯). As shown
in [6, 7], Monte Carlo event generators based on the Fritiof model [8, 9] cannot satisfactorily describe
the data. The most dramatic situation takes place with a description of the proton spectra. A typical
prediction for the xF -spectrum is shown in Figure 1 and is presented by the solid thin line.
arXiv:1410.6612v1 [hep-ph] 24 Oct 2014
PACS: 24.10.Lx, 13.85.-t,13.85.Ni, 14.20.-c
pp->p+X, 158 GeV/c
Figure 1: xF distributions of protons in pp interactions at 158 GeV/c. Closed points are the
NA49 experimental data [5]. Lines are results of FTF model simulations: standard proton
splitting (solid black), optimal diquark fragmentation function (dashed red), string inversion
(dotted blue), diquark suppression (1/6 instead of 1/3) including the optimal fragmentation
function and the string inversion (solid thick).
Geneva, Switzerland
of Information Technologies, JINR, Dubna, Russia
3 Veksler and Baldin Laboratory of High Energy Physics, JINR, Dubna, Russia
2 Laboratory
arXiv:1410.6585v1 [hep-ph] 24 Oct 2014
October 21th, 2014
O. Coquand 1 2 , B. Machet 3
4 5 6
Abstract: 1-loop quantum corrections are shown to induce large effects on the refractive index n inside a graphene
strip in the presence of a constant and uniform external magnetic field B orthogonal to it. To this purpose, we
use the tools of Quantum Field Theory to calculate the photon propagator at 1-loop inside graphene in position
space, which leads to an effective vacuum polarization in a brane-like theory of photons interacting with massless
electrons at locations confined inside the thin strip (its longitudinal spread is considered to be infinite). The effects
factorize into quantum ones, controlled by the value of B and that of the electromagnetic coupling α, and a
transmittance function U in which the geometry of the sample and the resulting confinement of the γ e+ e− vertices
play major roles. They only concern the so-called “transverse-magnetic” polarization of photons, which suggests
(anisotropic) electronic spin resonance of the graphene-born virtual electrons. We consider photons inside the
visible spectrum and magnetic fields in the range 1-20 Tesla. At B = 0, quantum effects depend very weakly on
α and n is essentially controlled by U ; we recover, then, an opacity for visible light of the same order of magnitude
παvac as measured experimentally.
1 Ecole
Normale Sup´erieure, 61 avenue du Pr´esident Wilson, F-94230 Cachan
2 [email protected]
3 Sorbonne
Universit´e, UPMC Univ Paris 06, UMR 7589, LPTHE, F-75005, Paris, France
UMR 7589, LPTHE, F-75005, Paris, France.
5 Postal address: LPTHE tour 13-14, 4e` me e
´ tage, UPMC Univ Paris 06, BP 126, 4 place Jussieu, F-75252 Paris Cedex 05 (France)
6 [email protected]
arXiv:1410.6583v1 [hep-ph] 24 Oct 2014
Charm contribution to bulk viscosity
M. Laine and Kiyoumars A. Sohrabi
Institute for Theoretical Physics, Albert Einstein Center, University of Bern,
Sidlerstrasse 5, CH-3012 Bern, Switzerland
In the range of temperatures reached in future heavy ion collision experiments, hadronic
pair annihilations and creations of charm quarks may take place within the lifetime of the
plasma. As a result, charm quarks may increase the bulk viscosity affecting the early stages
of hydrodynamic expansion. Assuming thermalization, we estimate the charm contribution
to bulk viscosity within the same effective kinetic theory framework in which the light parton
contribution has been computed previously. The time scale at which this physics becomes
relevant is related to the width of the transport peak associated with the trace anomaly
correlator, and is found to be <
∼ 20 fm/c for T >
∼ 600 MeV.
October 2014
High-energy e+ e− photoproduction in the field of a heavy atom
accompanied by bremsstrahlung
P.A. Krachkov,1, 2, ∗ R.N. Lee,1, † and A. I. Milstein1, ‡
Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia
arXiv:1410.6566v1 [hep-ph] 24 Oct 2014
Novosibirsk State University, 630090 Novosibirsk, Russia
(Dated: October 27, 2014)
Helicity amplitudes and differential cross section of high-energy e+ e− photoproduction accompanied by bremsstrahlung in the electric field of a heavy atom are derived. The results are exact
in the nuclear charge number and obtained in the leading quasiclassical approximation. They correspond to the leading high-energy small-angle asymptotics of the amplitude. It is shown that, in
general, the Coulomb corrections essentially modify the differential cross section as compared to
the Born result. When the initial photon is circularly polarized the Coulomb corrections lead to
the asymmetry in the distribution over the azimuth angles ϕi of produced particles with respect
to the replacement ϕi → −ϕi .
PACS numbers: 32.80.-t, 12.20.Ds
Keywords: e+ e− photoproduction, bremsstrahlung, Coulomb corrections
Electronic address: peter˙[email protected]
Electronic address: [email protected]
Electronic address: [email protected]
Concerning the Nature of the Cosmic Ray Power Law Exponents
A. Widom and J. Swain
Physics Department, Northeastern University, Boston MA USA
Y.N. Srivastava
arXiv:1410.6498v1 [hep-ph] 15 Oct 2014
Physics Department, University of Perugia, Perugia IT
We have recently shown that the cosmic ray energy distributions as detected on earthbound, low
flying balloon or high flying satellite detectors can be computed by employing the heats of evaporation of high energy particles from astrophysical sources. In this manner, the experimentally well
known power law exponents of the cosmic ray energy distribution have been theoretically computed
as 2.701178 for the case of ideal Bose statistics, 3.000000 for the case of ideal Boltzmann statistics
and 3.151374 for the case of ideal Fermi statistics. By “ideal” we mean virtually zero mass (i.e.
ultra-relativistic) and noninteracting. These results are in excellent agreement with the experimental indices of 2.7 with a shift to 3.1 at the high energy ∼ PeV “knee” in the energy distribution. Our
purpose here is to discuss the nature of cosmic ray power law exponents obtained by employing conventional thermal quantum field theoretical models such as quantum chromodynamics to the cosmic
ray sources in a thermodynamic scheme wherein gamma and zeta function regulation is employed.
The key reason for the surprising accuracy of the ideal boson and ideal fermion cases resides in the
asymptotic freedom or equivalently the Feynman “parton” structure of the ultra-high energy tails
of spectral functions.
PACS numbers: 13.85.Tp, 13.85.Dz, 13.85.Lg
As in our preliminary work[1], we seek to understand
the nature of the power law exponents {α} which are employed to describe the energy distributions observed in
the cosmic rays continually bombarding our planet and
coming from astrophysical sources[2–4]. From the quantum field theory viewpoint we regard the cosmic rays as
standard model hadrons evaporating from sources and
moving away from such sources as a gaseous blowing
wind. Such a solar wind exists issuing from the center of
our own planetary system. These evaporating winds no
doubt also blow away from other astrophysical objects
such as neutron stars.
The starting point for defining cosmic ray power law
exponents was purely experimental. It is known[5] that
the energy distribution law of cosmic ray nuclei in the
energy range 5 GeV < E < 100 TeV via the differential
flux per unit time per unit area per steradian per unit
energy obeys
d4 N
1 GeV
1.8 nucleons
sec cm2 sr GeV
wherein the experimental power law exponent α ≈ 2.7.
At the “knee” of the distribution, i.e. at energy E ∼
1 PeV, there is a shift in the power law exponent to the
value α ≈ 3.1. In [1], we had computed theoretically the
ideal Bose index. Here we also compute the ideal Fermi
statistical index so that they read together as:
αBose = 2.701178 and αFermi = 3.151374 .
It would be well within experimental error to regard the
knee as a crossover between statistics which in concrete
physical evaporation terms merely means a crossover in
the composition of cosmic ray emission winds blowing
away from astrophysical sources. The critical values in
Eq.(2) are ideal in the sense that the particles are ultrarelativistic E ≈ c|p| and noninteracting. One might ponder why a non-interacting theory is so close to experimental reality. The answer resides in the asymptotic freedom
in the form of Feynman parton structure[6] of the ultrahigh energy tails of spectral functions.
To describe cosmic ray sources in terms of thermal
quantum field theoretical models, it is of some convenience to employ gamma and zeta function regulators
whose definitions are reviewed in Sec.II wherein the ideal
power law exponents are derived. That interactions apparently have little effect on the power law exponents
would seem to imply that the quantum spectral functions
are of the Feynman form[6] with Bose and Fermi operators being composites of quark operators. In the concluding Sec.III these points are qualitatively discussed.
Mathematical Details
The mathematics of gamma and zeta regulators resides
in the properties of classical special functions[7]. Starting
with the statistical index
η = 1 Bose, η = 0 Boltzmann and η = −1 Fermi,
IPPP/14/92, DCPT/14/184
Scalar Simplified Models for Dark Matter
Matthew R. Buckley,1 David Feld,1 and Dorival Gon¸calves2
arXiv:1410.6497v1 [hep-ph] 23 Oct 2014
Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA
Institute for Particle Physics Phenomenology, Department of Physics, Durham University, United Kingdom
(Dated: October 27, 2014)
We introduce a set of minimal simplified models for dark matter interactions with the Standard
Model, connecting the two sectors via either a scalar or pseudoscalar particle. These models have a
wider regime of validity for dark matter searches at the LHC than the effective field theory approach,
while still allowing straightforward comparison to results from non-collider dark matter detection
experiments. Such models also motivate dark matter searches in multiple correlated channels. In
this paper, we constrain scalar and pseudoscalar simplified models with direct and indirect detection
experiments, as well as from existing LHC searches with missing energy plus tops, bottoms, or
jets, using the exact loop-induced coupling with gluons. This calculation significantly affects key
differential cross sections at the LHC, and must be properly included. We make connections with
the Higgs sector, and conclude with a discussion of future searches at the LHC.
The case for the existence of dark matter is strong. Decades of evidence from multiple independent lines [1–4] reveal
that this form of matter has a significant role in the composition and evolution of our Universe (for a review, see e.g.,
Ref. [5]). No particle in the Standard Model is a suitable candidate for dark matter and so we need new physics to
explain it. Though we lack evidence of the nature of the dark sector, if particle dark matter has a mass at the TeV
scale or lower and was ever in thermal equilibrium in the early Universe, we have good reason to expect interactions
with the visible sector to be within reach of our present experiments. However, this is of course not guaranteed.
Perhaps the best known example of such dark matter is a weakly-interacting massive particle which becomes a
thermal relic with the appropriate energy density after freeze-out. This type of dark matter is realized in many
extensions of the Standard Model introduced to solve other problems of a theoretical nature (e.g. Naturalness and
Hierarchy). However, looking beyond this class of dark matter, even models of non-thermal dark matter often require
significant annihilation cross sections into either the Standard Model or some hidden sector, so as not to overclose
the Universe [6]. It is therefore well-motivated to search for dark sector particles in a range of experiments, including
the Large Hadron Collider (LHC).
When looking for dark matter, we can cast the experimental reach in terms of specific models of dark matter which
are UV-complete. These models usually have a number of additional new particles with more significant interactions
with the Standard Model than the dark matter itself. The canonical example of this sort is the supersymmetric
neutralino, which is accompanied by a host of new charged and colored superpartners. Despite the advantage of
UV-complete models, interpreting results in this way has some drawbacks: i) the results may be difficult to recast for
new models; ii) correlating results with non-collider experiments may be very dependent on UV-complete parameters;
iii) focusing on a specific high-energy model runs the risk of overlooking other experimentally interesting channels;
and iv) tuning the experimental selection criteria could reduce the sensitivity to other types of dark matter.
In order to approach the problem in a somewhat model-independent way while still allowing for comparison between
different classes of experiments, it has been useful to present the results of experimental searches in an effective field
theory (EFT) framework [7–9]. The EFT approach assumes contact term interactions between dark matter and SM
particles with the particle(s) connecting the two sectors integrated out of the low-energy spectrum. The validity of the
EFT approach diminishes in the regime where the momentum transfer cannot be neglected relative to the (unknown)
mass of the heavy particles. For direct detection this condition is usually satisfied, as long as mediators are not
extremely light, as the momentum scale is on the order of 10 keV. Indirect detection and thermal freeze-out involve
the annihilation of non-relativistic dark matter and so the EFT is applicable as long as the mediator is significantly
heavier than twice the dark matter mass, assuming no additional new particles in the theory [10].
However, when considering the production of dark matter at particle colliders through high pT visible particles
recoiling against invisible dark matter [11–21], the momentum transfer in dark matter pair production events is
large enough to render the EFT assumption invalid for a significant range of dark matter masses, couplings, and
mediator masses [16, 18, 20, 22–29]. As the momentum flowing through the production diagram is proportional to
both the transverse momentum of the dark matter particles (i.e. the missing transverse momentum, or MET) and
the transverse momentum of recoiling visible particles required for the trigger, this issue will be even more pressing
at the LHC Run-II, as the trigger requirements on MET and jet pT will be higher than those used in Run-I. Rather
than viewing the invalidity of the EFT formalism as a drawback, it should be seen as an optimistic statement: if dark
Prepared for submission to JHEP
arXiv:1410.6492v1 [hep-ph] 23 Oct 2014
Custodial Vector Model
Diego Becciolini1 Diogo Buarque Franzosi1 Roshan Foadi2,3 Mads T. Frandsen1
Tuomas Hapola4 Francesco Sannino1
CP3 -Origins and the Danish Institute for Advanced Study, University of Southern Denmark,
Campusvej 55, DK-5230 Odense M, Denmark
Department of Physics, University of Jyv¨
a, P.O. Box 35, FI-40014, University of Jyv¨
Department of Physics & Helsinki Institute of Physics, P.O. Box 64, FI-000140, University of
Helsinki, Finland
Institute for Particle Physics Phenomenology, Durham University, South Road, Durham DH1
Abstract: We analyze the Large Hadron Collider (LHC) phenomenology of heavy vector
resonances with a SU (2)L × SU (2)R spectral global symmetry. This symmetry partially
protects the electroweak S-parameter from large contributions of the vector resonances.
The resulting custodial vector model spectrum and interactions with the standard model
fields lead to distinct signatures at the LHC in the diboson, dilepton and associated Higgs
arXiv:1410.6489v1 [hep-ph] 23 Oct 2014
Physics Department, Temple University,
1835 N, 12th Street, Philadelphia, PA 19122-6082, USA
E-mail: [email protected]
Aix-Marseille Universit´e, D´epartement de Physique,
Facult´e des Sciences site de Luminy, 13288 Marseille, Cedex 09, France
E-mail: [email protected]
INFN, Sezione di Napoli,
Via Cintia, Napoli, I-80126, Italy
E-mail: [email protected]
We will describe the quantum statistical approach to parton distributions
allowing to obtain simultaneously the unpolarized distributions and the helicity distributions. We will present some recent results, in particular related
to the nucleon spin structure in QCD. Future measurements are challenging
to check the validity of this novel physical framework.
Key words: Gluon polarization; Proton spin; Statistical distributions PACS
numbers: PACS numbers: 12.40.Ee, 13.60.Hb, 13.88.+e, 14.70.Dj
Invited talk presented by J. Soffer at the ”‘QCD Evolution Workshop”’, May 12 16, 2014, Santa Fe, New Mexico, USA (to be published in World Scientific Conference
Prepared for submission to JHEP
NIKHEF 2014-043
arXiv:1410.6483v1 [hep-ph] 23 Oct 2014
Resummation of Double-Differential Cross Sections and
Fully-Unintegrated Parton Distribution Functions
Massimiliano Procura,a Wouter J. Waalewijn,b,c Lisa Zeuneb
Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics,
University of Bern, CH-3012 Bern, Switzerland
ITFA, University of Amsterdam, Science Park 904, 1018 XE, Amsterdam, The Netherlands
Nikhef, Theory Group, Science Park 105, 1098 XG, Amsterdam, The Netherlands
E-mail: [email protected], [email protected], [email protected]
Abstract: LHC measurements involve cuts on several observables, but resummed calculations are mostly restricted to single variables. We show how the resummation of a class
of double-differential measurements can be achieved through an extension of Soft-Collinear
Effective Theory (SCET). A prototypical application is pp → Z + 0 jets, where the jet veto
is imposed through the beam thrust event shape T , and the transverse momentum pT of the
Z boson is measured. A standard SCET analysis suffices for pT ∼ mZ T 1/2 and pT ∼ T ,
but additional collinear-soft modes are needed in the intermediate regime. We show how to
match the factorization theorems that describe these three different regions of phase space,
and discuss the corresponding relations between fully-unintegrated parton distribution functions, soft functions and the newly defined collinear-soft functions. The missing ingredients
needed at NNLL/NLO accuracy are calculated, providing a check of our formalism. We also
revisit the calculation of the measurement of two angularities on a single jet in JHEP 1409
(2014) 046, finding a correction to their conjecture for the NLL cross section at O(αs2 ).
Lecture notes on
“Quantum chromodynamics and statistical
St´ephane Munier
arXiv:1410.6478v1 [hep-ph] 23 Oct 2014
Centre de physique th´eorique, Ecole
Polytechnique, CNRS, Palaiseau, France.
The concepts and methods used for the study of disordered systems have proven useful
in the analysis of the evolution equations of quantum chromodynamics in the high-energy
regime: Indeed, parton branching in the semi-classical approximation relevant at high energies is a peculiar branching-diffusion process, and parton branching supplemented by saturation effects (such as gluon recombination) is a reaction-diffusion process. In these lectures,
we first introduce the basic concepts in the context of simple toy models, we study the properties of the latter, and show how the results obtained for the simple models may be taken
over to quantum chromodynamics.
1 Branching random walks and the Fisher-Kolmogorov-Petrovsky-Piscounov
1.1 Brownian motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Branching random walk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Solving the FKPP equation
2.1 Heuristic analysis of the equation . . . . . . . . . . . . . . .
2.2 Bramson’s theorem: traveling waves . . . . . . . . . . . . .
2.3 Heuristic derivation of the properties of the traveling waves
2.3.1 Asymptotic shape and velocity . . . . . . . . . . . .
2.3.2 Finite-time corrections . . . . . . . . . . . . . . . . .
2.4 “Dual” interpretation of the solution to the FKPP equation
2.5 Generalization to other branching-diffusion processes . . . .
3 Applications to QCD
3.1 QCD evolution at very high energies . . . . . . . . . . . . . . . .
3.2 QCD evolution as a branching random walk . . . . . . . . . . . .
3.3 Mapping the Balitsky-Kovchegov equation to the FKPP equation
3.3.1 Calculation of the eigenvalues of the BFKL kernel . . . .
3.3.2 Compact expression for the BFKL and BK equations . .
. . .
. . .
. .
. . .
. . .
∗ Lectures given at the “Huada school on QCD”, Central China Normal University, Wuhan, China, June 2-13,
Deuteron Electro-Disintegration at Very High
Missing Momenta
arXiv:1410.6770v1 [nucl-ex] 24 Oct 2014
K. Aniol
California State University L.A.
F. Benmokhtar
Carnegie Mellon University
W.U. Boeglin (spokesperson), P.E. Markowitz, B.A. Raue,
J. Reinhold and M. Sargsian
Florida International University
C. Keppel, M. Kohl
Hampton University
D. Gaskell, D. Higinbotham, M. K. Jones (co-spokesperson),G. Smith and
S. Wood
Jefferson Lab
S. Jeschonnek
Ohio State University
J. W. Van Orden
Old Dominion University
G. Huber
University of Regina
E. Piasetzky, G. Ron, R. Shneor
Tel-Aviv University
H. Bitao
Lanzhou University
X. Jiang, A. Puckett
Los Alamos National Laboratory
We propose to measure the D(e,e0 p)n cross section at Q2 = 4.25
(GeV/c)2 and xbj = 1.35 for missing momenta ranging from pm = 0.5
GeV/c to pm = 1.0 GeV/c expanding the range of missing momenta
explored in the Hall A experiment (E01-020). At these energy and
momentum transfers, calculations based on the eikonal approximation
have been shown to be valid and recent experiments indicated that
final state interactions are relatively small and possibly independent of
missing momenta. This experiment will provide for the first time data
in this kinematic regime which are of fundamental importance to the
study of short range correlations and high density fluctuations in nuclei.
The proposed experiment could serve as a commissioning experiment
of the new SHMS together with the HMS in Hall C. A total beam time
of 21 days is requested.
version 1.0
Estimate of cold nuclear matter effects on bottom production in d+Au collisions at
sN N = 200 GeV
Daniel Kikola1 and Andrzej Lipiec1
Warsaw University of Technology, Warsaw, Poland
(Dated: October 27, 2014)
We investigate modification of the bottom quark production due to cold nuclear matter effects
(CNM) at mid-rapidity in d+Au collisions at sN N = 200 GeV at RHIC. Our results indicate that
bottom production is not suppressed due to CNM effects in those collisions. We also found that
shadowing and initial kT breadboarding for charm quarks explains at low pT (pT < 3 GeV/c) the
enhancement of heavy flavor decay electron yield in d+Au collisions at sN N = 200 GeV compared
to p+p.
PACS numbers: 13.20.He, 14.40.Nd, 21.65.-f,25.40.-h
arXiv:1410.6503v1 [nucl-ex] 23 Oct 2014
High energy heavy ion collisions provide an opportunity to create in a laboratory a Quark Gluon Plasma,
QGP, a state of matter with quark and gluon degree
of freedom. Charm and bottom quarks are important
probes of the properties of the QGP because they are
created in the initial scatterings with large momentum
transfer and are expected to interact with the QGP differently than light quarks (see Ref. [1] and references
therein). For instance, studies of the heavy quark energy
loss in nucleus-nucleus collisions could provide information about transport properties of the created nuclear
It is important to measure charm and bottom production separately in ˚
a collisions to have a full picture
of energy loss for light and heavy quarks. This was
a major motivation for recently completed upgrades at
the STAR and PHENIX experiments at the Relativistic
Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. These upgrades include a micro-vertexing detectors: Heavy Flavor Tracker (HFT) at STAR and Silicon
Vertex Tracker (VTX) and Forward Silicon Vertex Detector (FVTX) at PHENIX, which allow measurement of
charm and bottom production. Charm will be measured
via direct reconstruction of hadronic decays of D mesons.
Electrons from semi-leptonic decays of bottom hadrons
(noted here as b → e) are the most feasible tools for bottom studies. STAR and PHENIX collected large data
samples of Au+Au collisions at sN N = 200 GeV which
will allow precise measurement of heavy quark production and their nuclear modification factors. For interpretation of these results, it is important to have an estimate
of so-called cold nuclear matter (CNM) effects for c and
b quarks i.e. modification of production not related to
the QGP formation.
Experimentally we address these effects by measuring
particle production in p+A or d+Au interactions. Such
data for b and c quarks are not available so far (charm
and bottom separation in p+A will be possible in 2016,
after p+A run at RHIC). However, it is crucial to have
an estimate of CNM effects on bottom quark production
when the first precise Au+Au data are available in 2015.
Moreover, current data for electrons from semi-leptonic
decays of heavy flavor hadrons, eHF , show an enhancement of the production in central and minimum bias
d+Au collisions at mid-rapidity at RHIC [2]. Recent observations of collective behavior of light hadrons in d+Au
collisions at RHIC and p+A at LHC triggered speculations that this enhancement is an indication of collective
phenomena (radial flow) for heavy quarks in d+Au [3].
However, this enhancement could be also owing to the
CNM effects.
In this paper we estimate the modification of the bottom quark production due to cold nuclear matter effects
at top RHIC energy. First, we make a minimal set of assumptions about those effects for charm and we simulate
electrons from charmed meson decays (c → e) in d+Au
reactions. We consider initial transverse momentum (kT )
broadening of partons and modification of the parton distribution function in a nucleon in a nucleus compared to
a free proton (so called shadowing). Then we simulate
c → e in d+Au with those CNM included
√ using measured
charm pT spectrum in p+p collisions at s = 200 GeV as
an input. Then we subtract c → e contribution from eHF
yield measured by PHENIX collaboration to obtain electrons from bottom hadron decays. We also investigate
if the eHF enhancement can be explained by established
cold nuclear matter effects namely kT broadening and
We use√charm differential cross section in p+p collisions at s = 200 GeV as input in our simulations.
We construct the input spectra by combining the published STAR data [4] and recent preliminary results [5].
The pT spectrum is parametrized with a Levy function
m2T −mD −n
f (pT ) = A nT (nT
) , where A,
+mD (n−2)) (1 +
T and n are free parameters,
is D0 mass and mT =
m2D + pT 2 . We chose this
parametrization because it represents charm pT spectrum in a broad pT range (1-18 GeV/c) in p+p colli-