1. No category

arXiv:1410.4514v1 [nucl-ex] 16 Oct 2014
Beamline Instrumentation for Future
Parity-Violation Experiments
Robert Michaels
Thomas Jefferson National Accelerator Facility, 12000 Jefferson Ave, Newport News, VA
23608 USA
E-mail: [email protected]
Abstract. The parity-violating electron scattering community has made tremendous progress
over the last twenty five years in their ability to measure tiny asymmetries of order 100 parts
per billion (ppb) with beam-related corrections and systematic errors of a few ppb. Future
experiments are planned for about an order of magnitude smaller asymmetries and with higher
rates in the detectors. These new experiments pose new challenges for the beam instrumentation
and for the strategy for setting up the beam. In this contribution to PAVI14 I discuss several
of these challenges and demands, with a focus on developments at Jefferson Lab.
1. Introduction
Parity-violation experiments exploit the fact that a component of the weak interaction changes
sign under a parity transformation, which isolates the effects due to the weak interaction and
provides a tool to study a variety of physics topics. In electron scattering experiments, the
parity is transformed by reversing the longitudinal spin, or helicity, of the incident electrons.
This method relies crucially on a clean helicity reversal, such that no other beam parameter,
e.g. the angle or the energy, is affected. Such effects would cause a systematic error since the
much larger electromagnetic interaction is very sensitive to these parameters.
2. Setting up the Electron Beam
In an ideal electron-scattering parity-violation experiment, the two beams corresponding to the
two helicity states would be identical. In practice, however, imperfections in the laser optics
system at the polarized source will produce some level of coupling of the helicity to other beam
properties. The enormous efforts to suppress this coupling at the laser source is described in
several references (e.g. [1, 2]) and will not be discussed here. The experience at Jefferson Lab is
that after these efforts one is left with residual helicity-correlated beam position differences of
typically 50 nm in the beam at the injector which need further suppression.
2.1. Adiabatic Damping
Linear beam optics in a perfectly tuned accelerator can lead to a reduction in position differences
from the injector to the experimental hall due to the adiabatic damping of phase space area for
a beam undergoing acceleration [3]. The projected beam size and divergence, and thus the
difference orbit amplitude (defined as the size of the excursion from the orbit of the design
tune), are proportional to the square root of the emittance multiplied by the beta function at
arXiv:1410.4458v1 [physics.ins-det] 16 Oct 2014
Synthesis of neutron-rich transuranic nuclei in fissile
spallation targets
Igor Mishustina,b , Yury Malyshkina,c , Igor Pshenichnova,c , Walter Greinera
a Frankfurt
Institute for Advanced Studies, J.-W. Goethe University, 60438 Frankfurt am
Main, Germany
b “Kurchatov Institute”, National Research Center, 123182 Moscow, Russia
c Institute for Nuclear Research, Russian Academy of Science, 117312 Moscow, Russia
Abstract
A possibility of synthesizing neutron-reach super-heavy elements in spallation targets of Accelerator Driven Systems (ADS) is considered. A dedicated software called Nuclide Composition Dynamics (NuCoD) was developed
to model the evolution of isotope composition in the targets during a long-time
irradiation by intense proton and deuteron beams. Simulation results show that
transuranic elements up to
249
Bk can be produced in multiple neutron capture
reactions in macroscopic quantities. However, the neutron flux achievable in a
spallation target is still insufficient to overcome the so-called fermium gap. Further optimization of the target design, in particular, by including moderating
material and covering it by a reflector will turn ADS into an alternative source
of transuranic elements in addition to nuclear fission reactors.
1. Introduction
Neutrons propagating in a medium induce different types of nuclear reactions
depending on their energy. Apart of the elastic scattering, the main reaction
types for low-energy neutrons are fission and neutron capture, which dominate,
respectively, at higher and lower energies with the boarder line around 1 MeV.
Generally, the average number of neutrons captured by a nucleus A during a
time interval of ∆t is given by the formula:
∆N = f σnA ∆t ,
(1)
Email addresses: [email protected] (Igor Mishustin),
[email protected] (Yury Malyshkin), [email protected]
(Igor Pshenichnov)
Preprint submitted to Elsevier
October 17, 2014
Preprint typeset in JINST style - HYPER VERSION
arXiv:1410.4420v1 [physics.ins-det] 16 Oct 2014
Achievements of the ATLAS Upgrade Planar Pixel
Sensors R&D Project
C. Nellista∗, on behalf of the PPS Collaboration
a Laboratoire
de l’Accélérateur Linéaire, CNRS
Bat. 200, 9140, Orsay, France.
E-mail: [email protected]
A BSTRACT: In the framework of the HL-LHC upgrade, the ATLAS experiment plans to introduce
an all-silicon inner tracker to cope with the elevated occupancy.
To investigate the suitability of pixel sensors using the proven planar technology for the upgraded
tracker, the ATLAS Planar Pixel Sensor R&D Project (PPS) was established comprising 19 institutes and more than 90 scientists. The paper provides an overview of the research and development
project and highlights accomplishments, among them: beam test results with planar sensors up to
innermost layer fluences ( > 1016 neq cm−2 ); measurements obtained with irradiated thin edgeless
n-in-p pixel assemblies; recent studies of the SCP technique to obtain almost active edges by postprocessing already existing sensors based on scribing, cleaving and edge passivation; an update on
prototyping efforts for large areas: sensor design improvements and concepts for low-cost hybridisation; comparison between Secondary Ion Mass Spectrometry results and TCAD simulations.
Together, these results allow an assessment of the state-of-the-art with respect to radiation-hard
position-sensitive tracking detectors suited for the instrumentation of large areas.
K EYWORDS : Particle tracking detectors; Radiation-hard detectors; Large detector systems for
particle and astroparticle physics.
∗ Corresponding
author.
Observation of the Fundamental Nyquist Noise Limit in an Ultra-High Q-Factor
Cryogenic Bulk Acoustic Wave Cavity
Maxim Goryachev,1, ∗ Eugene N. Ivanov,1 Frank van Kann,2 Serge Galliou,3 and Michael E. Tobar1
arXiv:1410.4293v1 [physics.ins-det] 16 Oct 2014
1
ARC Centre of Excellence for Engineered Quantum Systems,
University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia
2
School of Physics, University of Western Australia,
35 Stirling Highway, Crawley WA 6009, Australia
3
Department of Time and Frequency, FEMTO-ST Institute,
´
ENSMM, 26 Chemin de l’Epitaphe,
25000, Besan¸con, France
(Dated: October 17, 2014)
Thermal Nyquist noise fluctuations of high-Q Bulk Acoustic Wave (BAW) cavities have been
observed at cryogenic temperatures with a DC Superconducting Quantum Interference Device
(SQUID) amplifier. High Q modes with bandwidths of few tens of milliHz produce thermal fluctuations with a Signal-To-Noise ratio of up to 23dB. The estimated effective temperature from the
Nyquist noise is in good agreement with the physical temperature of the device, confirming the
validity of the equivalent circuit model and the non-existence of any excess resonator self-noise. The
measurements also confirm that the quality factor remains extremely high (Q > 108 at low order
overtones) for very weak (thermal) system motion at low temperatures, when compared to values
measured with relatively strong external excitation. This result represents an enabling step towards
operating such a high-Q acoustic device at the standard quantum limit.
Phonon-trapping Bulk Acoustic Wave (BAW) cavity
resonator technology shows great potential for use in applications that require precision control, measurement
and sensing at the quantum limit[1]. This is mainly
due to the relatively high mechanical frequencies and extremely high Q-factors achievable in such devices at cryogenic temperatures (Q > 109 ), which potentially lead to
extraordinarily large coherence times [2–4] beyond the
capability of any other competing technology compared
in [5]. This uniqueness has been perfected for decades
for precision room temperature oscillators and related
devices[6, 7], culminating in Q × f -products as high as
2 · 1013 Hz [8]. Interestingly, it is no longer the deficiency
of the Q-factor, which halts further progress in the reduction of phase fluctuations, but rather the intrinsic fluctuations of the BAW resonator itself[9, 10]. In particular,
it has been concluded that further improvement of BAW
based frequency sources could only be achieved by reducing the resonator flicker phase self-noise, since this is
the dominant noise source of ultra-stable BAW oscillators
both at cryogenic and room temperature[9, 11].
The origin of the flicker frequency noise is still poorly
understood despite its significant influence on many
systems[12, 13] ranging from biological substances[14] to
superconducting electronics[15, 16]. The influence on
the frequency stability of high-performance quartz oscillators on time scales of order 1-10 seconds is welldocumented[10, 17, 18] with several attempts to understand its origins[19–21]. It is also important for other mechanical resonators such as High Overtone[22] and Thin
Film[23] BAW devices. On the other hand, coherence
times of ultra-high Q quartz BAW cavities are predicted
∗
[email protected]
to exceed 10 seconds. Thus, the question of the influence
of low Fourier frequency noise has never been raised with
respect to these types of measurements due to the relatively low Q factors of the mechanical resonators utilised
so far[24–26]. So, this type of noise can be another limiting factor on the coherence times of these devices, as
it can be for some types of superconducting qubits due
to flicker noise in Josephson junctions[27]. On the other
hand, it has been observed that the flicker self-noise decreases with decreasing power of the incident signal, and
there have been no reports of the measurement of selfnoise without the carrier. Thus, one of the goals of this
work was to confirm whether or not BAW devices are
dominated by Nyquist noise (due to quantum or thermal
fluctuations) when the carrier is not present. Thus, the
observation of intrinsic Nyquist fluctuations is an important step towards preparation of a BAW resonator in the
quantum ground state.
The fact that the Nyquist thermal noise of BAW devices has never been directly observed experimentally is
mostly due to instrumental limitations. In particular,
measurements of thermal noise require low noise amplification with effective impedance matching. Whereas for
low (tens-hundreds of kHz) frequencies typical for tuningfork type devices, the goal could be achieved by utilizing
high input impedance amplifiers, these type of amplifiers are non-existent at the typical cryogenic BAW frequencies (above 5-10 MHz), making such measurements
rather challenging[28]. Furthermore, the optomechanical
approach[5] to thermal noise measurements can not be
applied directly, since mirror coating a BVA (electrodeless) BAW resonator[29] would immediately result in Qfactor degradation. With these limitations, the straightforward solution is utilisation of a DC Superconducting
Quantum Interference Device (SQUID) Amplifiers[30, 31]
which ensure very high sensitivity. Such amplifiers have
Simulation of background reduction and Compton depression in lowbackground HPGe spectrometer at a surface laboratory
NIU Shun-Li(牛顺利)1;1 CAI Xiao(蔡啸)1;2 WU Zhen-Zhong(吴振忠)1 XIE Yu-Guang(谢宇广)1
YU Bo-Xiang(俞伯祥)1 WANG Zhi-Gang(王志刚)1 FANG Jian(方建)1 SUN Xi-Lei(孙希磊)1
SUN Li-Jun(孙丽君)1 LIU Ying-Biao(刘颖彪)12 GAO Long (高龙)12 ZHANG Xuan (张煊)12
ZHAO Hang(赵航)12 ZHOU Li(周莉)1 LV Jun-Guang(吕军光)1 HU Tao(胡涛)1
（1 State Key Laboratory of Particle Detection and Electronics, (Institute of High Energy Physics,Chinese Academy of
Sciences) Beijing 100049, China；2 University of Chinese Academy of Sciences, Beijing 100049, China）
Abstract：High-purity germanium detectors are well suited to analysis the radioactivity of samples. In order to
reduce the environmental background, low-activity lead and oxygen free copper are installed outside of the probe to
shield gammas, outmost is a plastic scintillator to veto the cosmic rays, and an anti-Compton detector can improve
the Peak-to-Compton ratio. Using the GEANT4 tools and taking into account a detailed description of the detector,
we optimize the sizes of the detectors to reach the design indexes. A group of experimental data from a HPGe
spectrometer in using were used to compare with the simulation. As to new HPGe Detector simulation, considering
the different thickness of BGO crystals and anti-coincidence efficiency, the simulation results show that the optimal
thickness is 5.5cm, and the Peak-to-Compton ratio of 40K is raised to 1000 when the anti-coincidence efficiency is
0.85. As the background simulation, 15 cm oxygen-free copper plus 10 cm lead can reduce the environmental gamma
rays to 0.0024 cps/100 cm3 Ge (50keV~2.8MeV), which is about 10-5 of environmental background.
Key words：HPGe, Geant4 Simulation, Gamma background, Anti-Compton ratio
PACS：29.30.Kv, 29.40.Wk
1.
Introduction
High-purity germanium (HPGe) detectors are widely used for different experimental researchs, such as neutrino
experiments and dark matter experiments. Due to its high energy resolution and efficiency, HPGe detectors are also
used to analyze the radioactive of material. IHEP had built a HPGe detector three years ago, used for the lowradioactive materials selected for Daya Bay experiment. But for the future Jiangmen Underground Neutrino
Observatory (JUNO) experiments, a more restrict low background experiment, it is beyond the current HPGe's ability,
so a ultra low-background HPGe spectrometer is required. It plays a very important role in these experiments to
minimize the background, i.e. the natural radioactivity from the lab materials and cosmic ray. To reduce the adverse
effects of cosmic rays[1,2], and improve the detection ability of uranium and thorium, there are some general ways,
such as moving to underground or cave, using high purity and high density setup materials to shield the gamma, for
example, low-background lead and oxygen-free copper. But it is costly and inconvenient. Most of the surface labs,
by adding cosmic veto detectors and shielding setup materials to reduce the integral background count-rate of HPGe
Spectrometer. It can remove the Compton plateau further reduce the background by placing an anti-Compton detector
surround the HPGe probe. It is impossible to completely reject these background, especially the cosmic ray muons
for surface labs. The environmental gamma background, with energy below 3 MeV, can be depressed mostly by
proper shielding materials, so it is crucial to estimate the accurately dimensions. Based on Geant4 Monte-Carlo
Study o n the unfolding a lgo rithm for D-T neutron energy spectra measurement
using recoil proton method *
WANG Jie(王洁)1
LU Xiao-Long(卢小龙) 1,2
WANG Jun-Run(王俊润)1
RAN Jian-Ling(冉建玲)1
LAN Chang-Lin(兰长林)1,2
1
2
YA N Yan(严岩) 1
W EI Zheng(韦峥) 1
HUANG Zhi-Wu(黄智武)1
YAO Ze-en(姚泽恩)1,2;1 )
School of Nuclear Sciences and T echnology, Lanzhou University, Lanzhou 730000, China
Engineering Research Center for Neutron Application, Ministry of Education, Lanzhou University, Lanzhou 730000, China
Abstract：A proton recoil method for measuring D-T neutron energy spectra using polyethylene film and Si (Au)
surface barrier detector was presented. An iteration algorithm for unfolding the recoil proton energy spectrum to the
neutron energy spectrum was investigated. The response matrixes R of polyethylene film at 0 degree and 45 degree
were obtained by simulating the recoil proton energy spectra from the mono-energetic neutron using MCNP code.
Under an assumed D-T neutron spectrum, the recoil proton spectra from polyethylene film at 0 degree and 45 degree
were also simulated using MCNP code. Based on the response matrixes R and the simulated recoil proton spectra at 0
degree and 45 degree, the unfolded neutron spectra were respectively obtained using the iteration algorithm, and
compared with the assumed neutron spectrum. The results show that the iteration algorithm method can be applied to
unfold the recoil proton energy spectrum to the neutron energy spectrum for D-T neutron energy spectra measurement
using recoil proton method.
Key words: D-T neutron source, recoil proton energy spectra, D-T neutron energy spectra, iteration algorithm method,
MCNP code
PACS: 29.25.Dz, 29.30.Ep, 29.30.Hs
1
Introduction
In 1988, a 3.3×1012 n/s neutron generator (ZF-300) based on T(d, n)4 He (D-T) reaction with a
rotating target had been built at Lan zhou University [1]. It had been applied in the research fields of
nuclear data measurements, radiation hardening and radioactive breeding [2]. A h igher intensity D-T
neutron generator is being developed at our laboratory. In the applications of D-T neutron generator,
neutron energy spectrum is one of the most important parameters. In previous investigations, a
mathematical method had been developed to calculate the energy spectrum fro m D-T reaction in a
thick tritiu m-titaniu m target for the incident deuteron beam in energy lower 1.0MeV[3]. In addition, a
Monte-Carlo simu lation research and an experimental measurement using nuclear emu lsion detector
also had been carried out fo r the neutron energy spectrum of ZF-300 D-T neutron generation [4].
However, because of the energy resolution of nuclear emu lsion detector is poor, the agreement between
simu lation results and experimental data is not very good.
In recent years, scintillation detector has been used to measure D-T fast neutron energy
spectrum[5-7]. However, the scintillation detector need a complex electronic system to distinguish the
neutron signal and γ-ray signal[8]. In order to avoid the use of comp lex electronic system, we put
forward a proton recoil method for measuring D-T neutron energy spectrum using polyethylene film
*Supported by the National Natural Science Foundation of China (11375077) and the National Natural Science Foundation of
China (21327801).
1)
E-mail: [email protected]
Method of Controlling Corona Effects and
Breakdown Voltage of Small Air Gaps Stressed by
Impulse Voltages
Athanasios Maglaras#1, Trifon Kousiouris*2, Frangiskos Topalis*3, Dimitrios Katsaros$4,
Leandros A. Maglaras$4, Konstantina Giannakopoulou #5
#
Electrical Engineering Department,
T.E.I. of Larissa, 41110 Larissa, Greece
[email protected]
[email protected]
*
Electrical and Computer Engineering Department, N.T.U.A.
9, Iroon Polytechniou str.
157 80 Athens, Greece
[email protected]
[email protected]
$
Computers, Telecommunications and Networks Engineering Department, University of Thessaly
37 Glavani – 28th October Str
Deligiorgi Building, 382 21 Volos, Greece
[email protected]
[email protected]
Abstract— This paper investigates the influence of a resistor
on the dielectric behavior of an air gap. The resistor is connected
in series with the air gap and the latter is stressed by impulse
voltage. Air gap arrangements of different geometry with either
the rod or the plate grounded are stressed with impulse voltages
of both positive and negative polarity. The resistor is connected
in series with the air gap in the return circuit connecting the gap
with the impulse generator. The method followed involves the
investigation of the graphs of the charging time concerning the
air gaps capacitances, in connection to the value of the resistor,
the geometry of the gap, the effect of grounding and the polarity
effect. It is determined that the charging time of the air gap
increases, as the value of the resistor increases. It is also
determined that the peak voltage value of the fully charged air
gap decreases as the value of the resistor increases. The results of
the mathematical and simulation analysis are compared with the
results of the oscillograms taken from experimental work. In
addition and consequently to the above results it is concluded
from the experimental work that the in series connection of the
resistor in the circuit has significant influence on corona pulses
(partial discharges) occurring in the gap and on the breakdown
voltage of the gap. A new method of controlling the corona effects
and consequently the breakdown voltage of small air gaps
stressed by impulse voltage of short duration in connection to the
ground effect and the polarity effect has arisen. Furthermore
through mathematical analysis of the charging graphs obtained
from simulation and experimental oscillograms there was a
calculation of the values of the capacitance of the air gaps in
relation to their geometry and the results were compared to the
values calculated with mathematical analysis.
Keywords: air gap, corona, breakdown, impulse high voltage, field,
FEM
INTRODUCTION
Air as an insulator is the most used in various arrangements
and probably the best conventional solution for the most of the
high voltage applications. The air gap thus is considered as
one of the most important parameters for the design and
dimensioning of insulating arrangements, in almost every
electrotechnical application.
In designing nearly every electrical arrangement, air gaps
are essential components that arise necessarily in
constructions (switches, gaps between power lines, or power
lines and earth, gaps between electrical and electronic
components in most devices, etc.), and they are stressed by dc
ac or impulse voltages.
The basic effects which are referred as the dielectric
behavior of an air gap are the corona effects and the
breakdown voltage, [1-3]. The basic magnitudes which
describe the dielectric behavior of an air gap are the corona
onset voltage, the corona current or pulses, the breakdown
voltage, and dielectric strength, [1-6].
The most known effects which influence the values of the
above mentioned magnitudes are, the polarity effect, [1-3],
[7-10] and the barrier effect. Other lately investigated
phenomena which have great influence on the dielectric
behavior of the air gaps are the ground effect, that is the
influence of the different electrode of the gap chosen to be
grounded on the field distribution and hence the dielectric
behavior of a gap [11-13], and the corona current effect, that is
the influence of the corona current on the dc breakdown
voltage of an air gap.
Electron/gamma and alpha backgrounds in CRESST-II Phase 2
R. Strauss,1, 2, ∗ G. Angloher,1 A. Bento,3 C. Bucci,4 L. Canonica,4 A. Erb,2, 5 F.v. Feilitzsch,2 N. Ferreiro Iachellini,1
P. Gorla,4 A. G¨
utlein,6 D. Hauff,1 J. Jochum,7 M Kiefer,1 H. Kluck,6 H. Kraus,8 J.-C. Lanfranchi,2
7
J. Loebell, A. M¨
unster,2 F. Petricca,1 W. Potzel,2 F. Pr¨obst,1 F. Reindl,1 S. Roth,2 K. Rottler,7 C. Sailer,7
4
K. Sch¨
affner, J. Schieck,6 S. Scholl,7 S. Sch¨onert,2 W. Seidel,1 M.v. Sivers,2, † L. Stodolsky,1 C. Strandhagen,7
A. Tanzke,1 M. Uffinger,7 A. Ulrich,2 I. Usherov,7 S. Wawoczny,2 M. Willers,2 M. W¨
ustrich,2 and A. Z¨
oller2
1
Max-Planck-Institut f¨
ur Physik, D-80805 M¨
unchen, Germany
Physik-Department, Technische Universit¨
at M¨
unchen, D-85748 Garching, Germany
3
CIUC, Departamento de Fisica, Universidade de Coimbra, P3004 516 Coimbra, Portugal
4
INFN, Laboratori Nazionali del Gran Sasso, I-67010 Assergi, Italy
5
Walther-Meißner-Institut f¨
ur Tieftemperaturforschung, D-85748 Garching, Germany
6
¨
Institut f¨
ur Hochenergiephysik der Osterreichischen
Akademie der Wissenschaften, A-1050 Wien, Austria
and Atominstitut, Vienna University of Technology, A-1020 Wien, Austria
7
Physikalisches Institut, Eberhard-Karls-Universit¨
at T¨
ubingen, D-72076 T¨
ubingen, Germany
8
Department of Physics, University of Oxford, Oxford OX1 3RH, United Kingdom
(Dated: October 17, 2014)
arXiv:1410.4188v1 [physics.ins-det] 15 Oct 2014
2
The experiment CRESST-II aims at the detection of dark matter with scintillating CaWO4 crystals operated as cryogenic detectors. Recent results on spin-independent WIMP-nucleon scattering
from the CRESST-II Phase 2 allowed to probe a new region of parameter space for WIMP masses
below 3 GeV/c2 . This sensitivity was achieved after background levels were reduced significantly.
We present extensive background studies of a CaWO4 crystal, called TUM40, grown at the Technische Universit¨
at M¨
unchen. The average beta/gamma rate of 3.44/[kg keV day] (1-40 keV) and the
total intrinsic alpha activity from natural decay chains of 3.08±0.04 mBq/kg are the lowest reported
for CaWO4 detectors. Contributions of gamma lines resulting from cosmogenic activation, external
X-rays and intrinsic beta emitters are investigated in detail.
I.
INTRODUCTION
During the last two decades, the sensitivity of experiments aiming for the direct detection of particle
dark matter [1] in form of weakly interacting massive
particles (WIMPs) [2] has been constantly improved.
For the spin-independent WIMP-nucleon cross section
impressive sensitivities were reached: currently the
liquid-xenon based LUX [3] experiment reports the best
upper limit (7.6 · 10−10 pb at 33 GeV/c2 ). A variety
of experiments with different techniques [4] have been
operated, however, the results are not consistent. A
few experiments [5–7], among which is CRESST-II
(Cryogenic Rare Event Search with Superconducting
Thermometers) [8], reported a signal excess which is excluded by other dark matter searches [9–12]. Data from
a re-analysis of the commissioning run of CRESST-II
[13] showed slight tension with a WIMP interpretation
of CRESST-II data and, recently, the first data of
CRESST-II Phase 2 [8] suggest a background origin of
the excess.
∗
†
Corresponding author; Electronic address: [email protected]
Present address: Albert Einstein Center for Fundamental
Physics, University of Bern, CH-3012 Bern, Switzerland
II.
THE DETECTOR MODULE TUM40
CRESST-II detectors are based on a two-channel detector readout which is the key feature to discriminate
irreducible radioactive backgrounds. CaWO4 crystals of
∼ 300 g each, equipped with transition-edge-sensors [14],
are operated as cryogenic detectors (called phonon detectors) which allow to measure precisely the total deposited
energy E of a particle interaction. An excellent energy
threshold of O(500 eV) and a resolution on a hlevel (at
2.6 keV) were achieved [8]. In addition, the scintillation
light output of these crystals is monitored by a cryogenic
silicon-on-sapphire detector (called light detector). Since
the relative amount of scintillation light, called light yield
LY , strongly depends on the kind of particle interaction
(due to quenching [15]) this channel provides a discrimination of beta/gamma, alpha and nuclear-recoil events.
To a certain extent even O, Ca and W recoils can be identified [16]. CRESST uses a unique multi-element target
for WIMP search in a single experiment.
Due to a finite resolution of the light channel, the
beta/gamma and nuclear-recoil bands overlap in the
region-of-interest (ROI) for dark matter search which is
typically defined between energy threshold and 40 keV.
Several background sources related to surface-alpha decays were identified in the previous run of CRESST-II
[17]. In particular 206 Pb nuclei from 210 Po decays on
surrounding surfaces limited the sensitivity. These events
appear at low LY similar to W recoils [18] and are thus
indistinguishable from potential WIMP scatters.
However, the decay of 210 Po has a corresponding al-
arXiv:1410.4505v1 [hep-ph] 16 Oct 2014
Modern Particle Physics Event Generation with
WHIZARD
J Reuter1 , F Bach1 , B Chokouf´
e1 , W Kilian2 , T Ohl3 , M Sekulla2 and
1,2
C Weiss
1
DESY Theory Group, Notkestr. 85, D–22607 Hamburg, Germany
University of Siegen, Department of Physics, Walter-Flex-Str. 3, D–57068 Siegen, Germany
3
University of W¨
urzburg, Department of Physics and Astronomy, Emil-Hilb-Weg 22, D–97074
W¨
urzburg
2
E-mail: [email protected], [email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected]
Abstract. We describe the multi-purpose Monte-Carlo event generator WHIZARD for the
simulation of high-energy particle physics experiments. Besides the presentation of the general
features of the program like SM physics, BSM physics, and QCD effects, special emphasis
will be given to the support of the most accurate simulation of the collider environments at
hadron colliders and especially at future linear lepton colliders. On the more technical side, the
very recent code refactoring towards a completely object-oriented software package to improve
maintainability, flexibility and code development will be discussed. Finally, we present ongoing
work and future plans regarding higher-order corrections, more general model support including
the setup to search for new physics in vector boson scattering at the LHC, as well as several
lines of performance improvements.
1. Introduction
WHIZARD [1] is a general event generator for all kinds of scattering and decay processes at highenergy hadron and lepton colliders.
The default matrix element generator of WHIZARD is O’Mega [2]. This latter subpackage
provides matrix elements for multi-leg tree-level processes, using the helicity formalism. The
high-dimensional phase-space integrations are performed by the multi-channel Monte-Carlo
integrator VAMP [3]. Its algorithm is adaptive both between and within channels, and thus
computes accurate phase-space integrals and efficiently generates weighted and unweighted event
samples.
The WHIZARD core acts as a connector of these different components. The core contains
the algorithm for multi-channel phase-space parameterization and mapping, provides the user
interface, and also interfaces external programs (e.g., parton distributions, event formats,
hadronization), the routines for writing and reading event files, and modules for parton shower
and jet physics. Further modules allow for the for numerical analyses and visualization of event
samples.
In order to be able to describe realistic ILC and CLIC environments, WHIZARD contains
a dedicated package for beam-spectrum simulation, CIRCE [4]. As an alternative, GuineaPig
The LHC Search for The CP-odd Higgs by The Jet Substructure Analysis
Ning Chen,1, ∗ Jinmian Li,2, † Yandong Liu,3, ‡ and Zuowei Liu4, §
1 Department
of Modern Physics, University of Science
arXiv:1410.4447v1 [hep-ph] 16 Oct 2014
and Technology of China, Hefei, Anhui, 230026, China
2 ARC
Centre of Excellence for Particle Physics at the Terascale,
School of Chemistry and Physics, University of Adelaide, Adelaide, SA 5005, Australia
3 Department
of Physics and State Key Laboratory of Nuclear Physics and Technology,
Peking University, Beijing 100871, China
4 Center
for High Energy Physics, Tsinghua University, Beijing, 100084, China
Abstract
The LHC searches for the CP-odd Higgs boson A is studied (with masses from 300 GeV to 1 TeV)
in the context of the general two-Higgs-doublet model. With the discovery of the 125 GeV Higgs
boson at the LHC, we highlight one promising discovery channel of the A → hZ. This channel can
become significant after the global signal fitting to the 125 GeV Higgs boson in the general twoHiggs-doublet model. It is particularly important in the scenario where two CP-even Higgs bosons
in the two-Higgs-doublet model have the common mass of 125 GeV. Since the final states involve a
Standard-Model-like Higgs boson, we apply the jet substructure analysis of the fat Higgs jet in order
to eliminate the Standard Model background sufficiently. After performing the kinematic cuts, we
present the LHC search sensitivities for the CP-odd Higgs boson with mass up to 1 TeV via this
channel.
PACS numbers: 12.60.Fr, 14.80.-j, 14.80.Ec,
∗
Electronic address:
Electronic address:
‡
Electronic address:
§
Electronic address:
†
[email protected]
[email protected]
[email protected]
[email protected]
1
Asymptotic Scenarios for the Proton’s Central
Opacity: An Empirical Study
D.A. Fagundes1, M.J. Menon2 , and P.V.R.G. Silva2
1
Instituto de F´ısica Te´
orica, Universidade Estadual Paulista , 01140-070 - S˜
ao Paulo, SP, Brazil
de F´ısica Gleb Wataghin, Universidade Estadual de Campinas , 13083-859 Campinas, SP,
Brazil
arXiv:1410.4423v1 [hep-ph] 16 Oct 2014
2 Instituto
Abstract
We present a model-independent analysis of the experimental data on the ratio X between
the elastic and total cross-sections from pp and p¯p scattering in the c.m. energy interval 5 GeV
- 8 TeV. Using a novel empirical parametrization for that ratio as a function of the energy
and based on theoretical and empirical arguments, we investigate three distinct asymptotic
scenarios: either the black-disk (BD) limit or scenarios above and below that limit. Our
analysis favors a scenario below the BD, with asymptotic ratio X = 0.36 ± 0.08.
PACS: 13.85.-t, 13.85.Lg, 11.10.Jj
Presented at Diffraction 2014, Primoˇsten, Croatia, September 10 - 16, 2014
The dependence of the ratio between the elastic and total hadronic cross-sections as a function of the
c.m. energy,
σel
X(s) =
(s),
(1)
σtot
constitutes an important quantity in the investigation of elastic and soft diffractive processes. Besides
giving information on the hadron’s central opacity (profile function at b = 0) and on the ratio of the
inelastic to total cross-sections, it is also connected with the ratio between the total cross section and the
elastic slope parameter through the approximated relation X = σtot /16πBel .
Presently, in the lack of a theoretical framework able to describe the elastic scattering states from the
first principles of QCD, one possible way to look for new phenomenological insights and/or inputs is the
empirical approach. In this context, Fagundes and Menon have recently developed a model-independent
analysis of the experimental data on the ratio X from pp scattering in the energy interval 10 GeV - 7 TeV
[1]. The empirical parametrization is given by X(s) = Af (s), with f (s) = tanh{a+b ln(s/s0 )+c ln2 (s/s0 )},
where s0 = 1 GeV2 , a, b, c are dimensionless free fit parameters and A the asymptotic limit. In order to
estimate the uncertainties in extrapolations to higher energies, two asymptotic limits have been considered:
either A = 1/2 (black-disk limit) or A = 1 (maximum unitarity). Beyond consistent data reductions of the
experimental information on X(s), the approximate relation has allowed extrapolations of the uncertainty
regions in the ratio σtot /Bel that may be useful in the determination of the proton-proton total crosssection from proton-air production cross-section in cosmic-ray experiments [1].
In this communication, this empirical analysis of the X data is updated and developed in several
aspects. The experimental data from p¯p scattering, all the pp TOTEM data at 7 TeV (four points) and
8 TeV (one point) are included in the dataset and the energy cutoff is down to 5 GeV. The description
of the change of curvature in X(s) demands a novel empirical ansatz for f (s) and as explained in what
follows, we investigate all the three possible asymptotic scenarios: either the black-disk limit or scenarios
above or below that limit.
The Black-Disk limit represents a standard phenomenological expectation, typical, for example, of
eikonal models. We have the arguments that follows for investigating scenarios either below or above that
limit.
1
EPJ Web of Conferences will be set by the publisher
DOI: will be set by the publisher
c Owned by the authors, published by EDP Sciences, 2014
arXiv:1410.4327v1 [hep-ph] 16 Oct 2014
MITP/14-014
η and η0 transition form factors from Padé approximants
Pablo Sanchez-Puertas1 , a and Pere Masjuan1
1
PRISMA Cluster of Excellence, Institut für Kernphysik,
Johannes Gutenberg-Universität, Mainz D-55099, Germany
Abstract. We employ a systematic and model-independent method to extract, from
space- and time-like data, the η and η0 transition form factors (TFFs) obtaining the most
precise determination for their low-energy parameters and discuss the Γη→γγ impact on
them. Using TFF data alone, we also extract the η − η0 mixing parameters, which are
compatible to those obtained from more sophisticated and input-demanding procedures.
1 Introduction
The hadronic structure of neutral pseudoscalar mesons may be probed via the two-photon mechanism.
The most general matrix element for such process is given by
MPγ∗ γ∗ = ie2 εµνρσ q1,µ 1,ν q2,ρ 2,σ F Pγ∗ γ∗ (q21 , q22 ),
(1)
where qi (i ) stands for the i-th photon momentum (polarization) and F Pγ∗ γ∗ (q21 , q22 ) is the pseudoscalar
transition form factor (TFF) encoding all the strong-interaction effects. Of particular interest is the
single virtual TFF F Pγ∗ γ (Q2 ) ≡ F Pγ∗ γ∗ (−q2 , 0) for which many measurements are available. At low
energies, the TFF can be expressed in terms of its low-energy parameters (LEPs) bP , cP , dP , ...

 4
 6

 2

 Q 
 Q 
 Q 

2
(2)
F Pγ∗ γ (Q ) = F Pγγ (0) 1 − bP  2  + cP  2  − dP  2  + ... .
mP
mP
mP
However, due to the non-perturbative behavior of QCD at low energies, neither the TFF, nor its LEPs,
can be calculated from first principles. Only its low- and high-energy limits are known from the axial
anomaly [1, 2] and perturbative QCD [3], respectively. Remarkably, both limits depend on the same
parameters. In this work [4], we focus on the η and η0 TFFs. Using the flavor basis to describe the
η − η0 mixing, these limits read
Fηγγ (0) = (ˆcq /Fq ) cos φ − (ˆc s /F s ) sin φ /4π2 ,
(3)
2
Fη0 γγ (0) = (ˆcq /Fq ) sin φ + (ˆc s /F s ) cos φ /4π ,
(4)
lim Q2 Fηγ∗ γ (Q2 ) = 2(ˆcq Fq cos φ − cˆ s F s sin φ) ,
(5)
lim Q2 Fη0 γ∗ γ (Q2 ) = 2(ˆcq Fq sin φ + cˆ s F s cos φ) ,
(6)
Q2 →∞
Q2 →∞
a e-mail: [email protected]. Supported by the Deutsche Forschungsgemeinschaft DFG through the Collaborative
Research Center “The Low-Energy Frontier of the Standard Model" (SFB 1044) and by the PRISMA Cluster of Excellence.
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–5
Charged Higgs Boson: Tracer of the Physics beyond Standard Model
Shou-hua Zhu
arXiv:1410.4310v1 [hep-ph] 16 Oct 2014
1
Institute of Theoretical Physics & State Key Laboratory of Nuclear Physics and Technology,
Peking University, Beijing 100871, China
2 Collaborative Innovation Center of Quantum Matter, Beijing, China
3 Center for High Energy Physics, Peking University, Beijing 100871, China
Abstract
Charged Higgs boson can exist in many physics beyond the standard models (BSM) and it is the obvious BSM
signal. We briefly describe why the 125GeV scalar discovered at the LHC must have (heavy) companion: the charged
Higgs boson, in a new paradigm. We then focus on the charged Higgs phenomenology, especially on how to measure
tan β precisely utilizing the top quark polarization information.
Keywords:
Charged Higgs Boson, Physics beyond Standard Model, LHC
1. Introduction
In July 2012, the new scalar (dubbed as H(125) in
this paper) was discovered by ATLAS and CMS of
the LHC, which surprised many theorists including me.
Furthermore the subsequent measurements are still consistent with the predictions of the standard model (SM).
Though the physics beyond the SM (BSM) has strong
motivations [1], the pursuit of it needs some courage and
a little bit of luck. During the ICHEP2014, I can feel the
spirit of Don Quijote, which is best described by a song
called ”The impossible dream”: ”To dream the impossible dream/ To fight the unbeatable foe/ To bear with
unbearable sorrow/ To run where the brave dare not go/
. . . /And the world will be better for this/ That one man
scorned and covered with scars/ Still strove with his last
ounce of courage/ To reach the unreachable star”.
Now that the neutral scalar H(125) was discovered,
one may wonder whether there are more scalars to be
discovered, especially the charged Higgs boson. It is
the obvious BSM signature. In the SM, one doublet is
enough to generate the gauge boson mass and fermion
mass, at the same time to induce the flavor changing
interactions with the right magnitude. It seems that no
extra scalars are needed. Therefore in second Sec. II,
we will briefly present the motivation for the charged
Higgs boson and in Sec. III, we discuss the different top
quark polarization in charged Higgs boson decay and in
associated production, In Sec. IV, we focus on how to
suppress the backgrounds assuming the charged Higgs
boson decaying into top plus bottom. In Sec V, we study
how to measure tan β utilizing the top polarization, especially for the intermediate value which is hard to measure using the cross section information, and last section
contains our conclusion and discussion.
2. Motivation for charged Higgs boson: A possible
new paradigm
Many BSM require more scalar sectors for various
reasons. For example, the minimum supersymmetric
standard model (MSSM) requires at least two Higgs
doublets.
In the last two years, we begin to realize a possible new paradigm [1] and the schematic diagram of
which is shown in Fig. 1. This conjectured new
paradigm is based on the assumption that correlation between the lightness of H(125) and the smallness of CP-
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–8
Global Bayesian Analysis of the Higgs-boson CouplingsI
Jorge de Blasa , Marco Ciuchinib , Enrico Francoa , Diptimoy Ghosha , Satoshi Mishimac,d , Maurizio Pierinie , Laura
Reinaf , Luca Silvestrinia
a INFN,
Sezione di Roma, Piazzale A. Moro 2, I-00185 Roma, Italy
Sezione di Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy
c Dipartimento di Fisica, Universit`
a di Roma “La Sapienza”, Piazzale A. Moro 2, I-00185 Roma, Italy
d SISSA, Via Bonomea 265, I-34136 Trieste, Italy
e CERN, CH-1211 Geneva 23, Switzerland
f Physics Department, Florida State University, Tallahassee, FL 32306-4350, USA
arXiv:1410.4204v1 [hep-ph] 15 Oct 2014
b INFN,
Abstract
We present preliminary results of a bayesian fit to the Wilson coefficients of the Standard Model gauge invariant
dimension-6 operators involving one or more Higgs fields, using data on electroweak precision observables and Higgs
boson signal strengths.
Keywords: Higgs boson, Effective field theory
1. Introduction
After a decades-long hunt, in the summer of 2012 the
physics world erupted in excitement when both the ATLAS and CMS experiments at the Large Hadron Collider (LHC) at CERN announced their discovery of a
particle that looked like the Higgs boson (H) [1, 2].
With the help of two-and-a-half times more data and sophisticated experimental analyses, it is now confirmed
that the newfound particle behaves, indeed, very much
like the Standard Model (SM) Higgs boson. That this
Higgs boson decays to SM gauge bosons is now established with high statistical significance. In fact, each of
I Based on a talk presented by Diptimoy Ghosh in the 37th International Conference on High Energy Physics (ICHEP) in Valencia
from the 2nd to the 9th July 2014.
Email addresses:
[email protected] (Jorge de Blas),
[email protected] (Marco Ciuchini),
[email protected] (Enrico Franco),
[email protected] (Diptimoy Ghosh),
[email protected] (Satoshi Mishima),
[email protected] (Maurizio Pierini),
[email protected] (Laura Reina),
[email protected] (Luca Silvestrini)
the decay channels H → γγ, H → W + W − and H → ZZ
is by now a discovery channel. There is also good evidence of its non-universal couplings to fermions. The
decays to τ+ τ− and b b¯ final states have also been seen
with good confidence.
Since the Higgs-boson mass (mH ) has now been measured, its couplings to SM particles are completely predicted except for the residual arbitrariness introduced
by the Yukawa couplings to fermions, which are nevertheless very constrained by the precise measurement of
fermion masses. This means that any deviation from the
SM predictions will provide unambiguous evidence for
New Physics (NP). Unfortunately, large deviations from
the SM expectations are already ruled out (except possibly in the couplings to light fermions and/or H → Zγ).
This, in conjunction with the absence of any other direct NP signal so far, leads us to expect a deviation at
the level of no more than a few percents. Hence, a rigorous study of the Higgs-boson couplings in the RunII of the LHC and also in the high luminosity phase is
mandatory.
Although new particles at the TeV scale or below
are perfectly allowed by the LHC data, it is interesting to study the sensitivity of the current Higgs-boson
Strong P invariance, neutron EDM and minimal Left-Right parity at LHC
Alessio Maiezza1, ∗ and Miha Nemevˇsek2, 3, 4, †
arXiv:1407.3678v2 [hep-ph] 15 Oct 2014
1
IFIC, Universitat de Val`encia-CSIC, Apt. Correus 22085, E-46071 Val`encia, Spain
2
SISSA, Trieste, Italy
3
INFN, Trieste, Italy
4
Joˇzef Stefan Institute, Ljubljana, Slovenia
(Dated: October 16, 2014)
In the minimal Left-Right model the choice of left-right symmetry is twofold: either generalized
parity P or charge conjugation C. In the minimal model with spontaneously broken strict P, a
large tree-level contribution to strong CP violation can be computed in terms of the spontaneous
phase α. Searches for the neutron electric dipole moments then constrain the size of α. Following
the latest update on indirect CP violation in the kaon sector, a bound on WR mass at 20 TeV is
set. Possible ways out of this bound require a further hypothesis, either a relaxation mechanism
or explicit breaking of P. To this end, the chiral loop of the neutron electric dipole moment at
next-to-leading order is re-computed and provides an estimate of the weak contribution. Combining
this constraint with other CP violating observables in the kaon sector allows for MWR & 3 TeV. On
the other hand, C-symmetry is free from such constraints, leaving the right-handed scale within the
experimental reach.
PACS numbers: 12.60.Cn, 11.30.Er, 12.15.Ff, 14.20.Dh
I.
INTRODUCTION
Left-Right(LR) symmetric theories [1] offer an understanding of parity violation [2] and neutrino mass origin through the see-saw mechanism [3]. This framework may be directly tested at the LHC via the KeungSenjanovi´c [4] production of a heavy Majorana neutrino [5]. Such observation would manifest lepton number
violation and Majorana nature of heavy neutrino directly
at high energies with a reach of WR mass at 5−6 TeV [6].
The underlying postulate of parity restoration makes
the minimal LR symmetric model (LRSM) predictive in
a number of ways. It constrains the flavor structure of
gauge and Higgs interactions and thus governs production at colliders, nuclear transitions such as neutrino-less
double beta decay [7, 8] (see also [9]), indirect constraints
and early universe processes such as thermal production
of warm dark matter [10]. It ensures a direct connection
between Majorana and Dirac masses, promoting LRSM
to a complete theory of neutrino mass [11].
The choice of LR parity however, is not unique. It
can be defined either as generalized parity P or charge
conjugation C, see e.g. [12]. The former may offer an
insight into the strong CP problem [13], while the latter
can be gauged and embedded in SO(10).
Indirect constraints on the LR scale have been intensely studied since the conception of LR theory. The
early bound from kaon mixing [14] was revisited a number of times [15, 16] demonstrating the scale of LRSM
is allowed within the reach of the LHC [12]. A recent
study [17] updates the limit to MWR & 3 TeV and highlights the importance of current and future constraints
∗
†
[email protected]
[email protected]
from B physics. Regardless of how one defines parity,
LR scale can be within the reach of LHC, as far as K
and B physics is concerned.
A particularly stringent probe of P and CP violating
interactions are electric dipole moments (EDM) of nucleons and atoms [18, 19]. After the initial suggestion to
use the neutron EDM (nEDM) as a probe of parity violation [20] and subsequent discovery of parity breaking in
weak interactions [21], the limit from early searches [22]
steadily improved by around 6 orders of magnitude [23].
In the Standard Model (SM), such searches constrain
˜ and lead to the so-called strong CP
the CPV θ term (GG)
problem, a quest to explain why this parameter should
be small. An attractive solution was put forth in [24] by
imposing a global Peccei-Quinn (PQ) symmetry. On the
other hand, since the θ term violates P (and CP), parity
restoration at high scales may offer a mechanism [13, 25],
different from the usual light axion [26].
LR theories at TeV scales typically give a significant
weak contribution to EDMs due to chirality flipping nature of gauge interactions. Short-distance effects from
quark EDMs [27, 28], the current-current operator [28]
and the Weinberg operator [29] were studied in the past.
The long distance contribution from the chiral loop was
estimated in [30], however the result disagrees with the
naive power counting [19, 31, 32]. This lead to a large
limit on MWR > 10 TeV coming from the weak contribution only [16, 33].
In this work we re-consider the issue of nEDM, taking
into account the strong CP contribution and an updated
chiral loop calculation. It is well known that a complex
vev in theories with spontaneous P or CP violation introduces a tree-level contribution to θ¯ [12]. Although it
vanishes in the mq → 0 limit, in the LRSM it comes out
Combining dark matter detectors and electron-capture sources to hunt for new
physics in the neutrino sector
Pilar Coloma,1, ∗ Patrick Huber,1, † and Jonathan M. Link1, ‡
arXiv:1406.4914v2 [hep-ph] 14 Oct 2014
1
Center for Neutrino Physics, Physics Department, Virginia Tech,
850 West Campus Dr, Blacksburg, VA 24061, USA
In this letter we point out the possibility to study new physics in the neutrino sector using dark
matter detectors based on liquid xenon. These are characterized by very good spatial resolution
and extremely low thresholds for electron recoil energies. When combined with a radioactive νe
source, both features in combination allow for a very competitive sensitivity to neutrino magnetic
moments and sterile neutrino oscillations. We find that, for realistic values of detector size and
source strength, the bound on the neutrino magnetic moment can be improved by an order of
magnitude with respect to the present value. Regarding sterile neutrino searches, we find that most
of the gallium anomaly could be explored at the 95% confidence level just using shape information.
I.
INTRODUCTION
Neutrinos have long been a rich hunting ground for
physics beyond the Standard Model (BSM). In fact, neutrino mass is so far the only BSM physics that has been
established in laboratory experiments. Astrophysical evidence of dark matter suggests the existence of BSM particles, which have nevertheless not been observed yet.
Among all feasible candidates, weakly interacting massive particles (WIMPs) are theoretically rather appealing. These may be observable through their interactions
within detectors, as the earth moves through the sea of
WIMPs. This possibility has triggered a cornucopia of
experimental efforts of direct dark matter detection [1].
In this letter we examine the physics potential of combining a liquid xenon (LXe) detector, designed to search
for WIMP dark matter, with an intense electron-capture
neutrinos source in order to look for neutrino magnetic
moments (νMM) and other new physics in νe e− elastic scattering. The idea of looking for new physics in the
neutrino sector using dark matter detectors has been proposed before in the literature, see for instance Refs. [2–5].
Direct dark matter detection relies on observing nuclear
recoils with electron-equivalent energy down to ∼ 1 keV.
Due to the small values expected for the dark matter
interaction cross section, large detector masses and low
background levels are also required. A LXe time projection chamber (TPC) can provide a large volume, low detection thresholds (sub-keV) and a very low background
rate at the energies of interest. At the same time the
electron density is higher in xenon than in any other stable noble gas, thus providing the largest possible target
density in any given volume near the source. The idea of
using liquid noble gas detectors to search for νMM was
first suggested by Vogel and Engel [6], but never developed. As a by-product we also find non-negligible sensi-
∗ Electronic
address: [email protected]
address: [email protected]
‡ Electronic address: [email protected]
† Electronic
tivity to sterile neutrino oscillations in the ∆m2 ∼1 eV2
range suggested by recent terrestrial experiments [7].
When a nucleus decays via electron-capture almost all
of the available energy goes into a mono-energetic neutrino. Among possible nuclei which decay via electroncapture, 51 Cr offers several practical advantages: it is
readily produced by thermal neutron capture [8], has
a mean lifetime of 39.96 days and produces two monoenergetic neutrino lines at 750 keV (90%) and 430 keV
(10%). Mega-curie-scale 51 Cr sources have been produced in the past and used to calibrate the gallium radiochemical solar neutrino detectors GALLEX [9, 10] and
SAGE [11].
II.
CONSTRAINTS ON THE NEUTRINO
MAGNETIC MOMENT
In the presence of a νMM, the differential cross section
for νe e− elastic scattering can be written as
2
dσ
dσ
πα2 1
1
µν
=
+ 2
−
, (1)
dT tot
dT SM me T Eν
µB
where me is the electron mass, T is the electron recoil energy, Eν is the neutrino energy and µν is the
νMM in Bohr magnetons (µB ). The term proportional
to µν produces an increase in the number of events at
low electron recoil energies. This makes two-phase LXe
TPCs [12–17], with their low-energy detection threshold,
ideal detectors for such a search. Currently, the lowest bounds on νMM come from astrophysical observations [18]: µν . 3 × 10−12 µB . The best constraint from
terrestrial experiments, on the other hand, has been obtained by the GEMMA experiment, µν < 2.9 × 10−11 µB
at 90% CL [19]. In the SM, νMMs are expected to be
many orders of magnitude below present bounds, yet
many extensions of the SM produce an enhancement
of the νMM, see for instance Ref. [20] and references
therein.
For our sensitivity estimate, we assume a data taking period of 100 days, using a 51 Cr source with initial
strength of 5 MCi. Our choice for the strength of the
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–6
Measurement of Top Quark Properties in Single Top-Quark Production at CMS
Efe Yazgan for the CMS Collaboration
arXiv:1410.4548v1 [hep-ex] 16 Oct 2014
Ghent University, CERN PH-UCM Bat 42 2-029 C28810, CH 1211 Geneva 23, Switzerland
Abstract
Single top-quark t-channel production is exploited for studies of top quark properties. The analyses include the
measurement of the CKM matrix element, |Vtb |, search for anomalous couplings of the top quark using a Bayesian
neural network analysis, measurement of single top-quark polarization which directly confirms the V-A nature of
the tWb production vertex, and the measurement of W-helicity fractions in the phase space sampled by a selection
optimized for t-channel single top-quark production, orthogonal to the tt final states used in traditional measurements
of these properties. All measurements are found to be consistent with the standard model predictions.
Keywords:
CMS, Hadron-hadron Scattering, Top Quark, CKM
1. Introduction
The top quark is the most massive particle known to
date. The top quark decays via the weak interaction and
due to its high mass, it has a very short lifetime which
is smaller than the hadronization time-scale, 1/ΛQCD .
Therefore, top quark properties can be measured before
being obscured by QCD effects. Single top-quarks are
produced through the electroweak interaction. At the
leading order, W boson virtuality is used to classify the
single top-quark production in s-, t-, and Wt-channels.
Single top-quark production is first observed in 2009
by both Tevatron experiments in the s + t channel using multi-variate techniques [1, 2]. In the subsequent
analyses by Tevatron and LHC experiments, all production modes are established [3, 4, 5]. Single top-quark
measurements provide tests of electroweak interactions,
and single top-quark production is sensitive to up and
down quark Parton Distribution Functions (PDFs). All
three production modes are sensitive to tWb-vertex and
hence, new physics. For example, tW- or s-channel
production is useful in W 0 and charged Higgs searches
and t-channel production can be used to look for flavor
changing neutral currents (FCNCs). In addition, single top-quark is background to Higgs boson and new
physics searches.
The dominant single top-quark process at the LHC
(and at the Tevatron) is the t-channel production, and
therefore top quark properties measurements using single top-quark production are made in this channel. The
Feynman diagram for this process is displayed in Figure 1. The t-channel production is characterized by the
Figure 1: Leading order Feynman diagrams for t-channel top quark
production.
existence of one isolated lepton, one light and relatively
forward jet, one central b-jet and missing transverse energy (
ET ). The main backgrounds are W+jets, tt and
QCD multi-jets. To test the standard model (SM) couplings in single top-quark t-channel, an effective field
EUROPEAN ORGANISATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP-2014-230
arXiv:1410.4409v1 [hep-ex] 16 Oct 2014
Submitted to: Physics Letters B
Search for the X b and other hidden-beauty states in the
π+ π− Υ(1S) channel at ATLAS
The ATLAS Collaboration
Abstract
This Letter presents a search for a hidden-beauty counterpart of the X(3872) in the mass ranges
10.05–10.31 GeV and 10.40–11.00 GeV, in the channel Xb → π+ π− Υ(1S)(→ µ+ µ− ), using 16.2 fb−1 of
√
s = 8 TeV pp collision data collected by the ATLAS detector at the LHC. No evidence for new narrow
states is found, and upper limits are set on the product of the Xb cross section and branching fraction,
relative to those of the Υ(2S), at the 95% confidence level using the CLS approach. These limits range
from 0.8% to 4.0%, depending on mass. For masses above 10.1 GeV, the expected upper limits from
this analysis are the most restrictive to date. Searches for production of the Υ(13 D J ), Υ(10860), and
Υ(11020) states also reveal no significant signals.
c 2014 CERN for the benefit of the ATLAS Collaboration.
Reproduction of this article or parts of it is allowed as specified in the CC-BY-3.0 license.
arXiv:1410.4267v1 [hep-ex] 16 Oct 2014
Test of Lorentz Invariance with Atmospheric Neutrinos
K. Abe,1, 29 Y. Haga,1 Y. Hayato,1, 29 M. Ikeda,1 K. Iyogi,1 J. Kameda,1, 29 Y. Kishimoto,1, 29 M. Miura,1, 29
S. Moriyama,1, 29 M. Nakahata,1, 29 Y. Nakano,1 S. Nakayama,1, 29 H. Sekiya,1, 29 M. Shiozawa,1, 29 Y. Suzuki,1, 29
A. Takeda,1, 29 H. Tanaka,1 T. Tomura,1, 29 K. Ueno,1 R. A. Wendell,1, 29 T. Yokozawa,1 T. Irvine,2 T. Kajita,2, 29
I. Kametani,2 K. Kaneyuki,2, 29, ∗ K. P. Lee,2 T. McLachlan,2 Y. Nishimura,2 E. Richard,2 K. Okumura,2, 29
L. Labarga,3 P. Fernandez,3 J. Gustafson,4 E. Kearns,4, 29 J. L. Raaf,4 J. L. Stone,4, 29 L. R. Sulak,4 S. Berkman,5
H. A. Tanaka,5 S. Tobayama,5 M. Goldhaber,6, ∗ G. Carminati,7 W. R. Kropp,7 S. Mine,7 P. Weatherly,7
A. Renshaw,7 M. B. Smy,7, 29 H. W. Sobel,7, 29 V. Takhistov,7 K. S. Ganezer,8 B. L. Hartfiel,8 J. Hill,8 W. E. Keig,8
N. Hong,9 J. Y. Kim,9 I. T. Lim,9 T. Akiri,10 A. Himmel,10 K. Scholberg,10, 29 C. W. Walter,10, 29
T. Wongjirad,10 T. Ishizuka,11 S. Tasaka,12 J. S. Jang,13 J. G. Learned,14 S. Matsuno,14 S. N. Smith,14
T. Hasegawa,15 T. Ishida,15 T. Ishii,15 T. Kobayashi,15 T. Nakadaira,15 K. Nakamura,15, 29 Y. Oyama,15
K. Sakashita,15 T. Sekiguchi,15 T. Tsukamoto,15 A. T. Suzuki,16 Y. Takeuchi,16 C. Bronner,17 S. Hirota,17
K. Huang,17 K. Ieki,17 T. Kikawa,17 A. Minamino,17 A. Murakami,17 T. Nakaya,17, 29 K. Suzuki,17 S. Takahashi,17
K. Tateishi,17 Y. Fukuda,18 K. Choi,19 Y. Itow,19 G. Mitsuka,19 P. Mijakowski,34 J. Hignight,20 J. Imber,20
C. K. Jung,20 C. Yanagisawa,20 H. Ishino,21 A. Kibayashi,21 Y. Koshio,21 T. Mori,21 M. Sakuda,21 R. Yamaguchi,21
T. Yano,21 Y. Kuno,22 R. Tacik,23, 31 S. B. Kim,24 H. Okazawa,25 Y. Choi,26 K. Nishijima,27 M. Koshiba,28
Y. Suda,28 Y. Totsuka,28, ∗ M. Yokoyama,28, 29 K. Martens,29 Ll. Marti,29 M. R. Vagins,29, 7 J. F. Martin,30
P. de Perio,30 A. Konaka,31 M. J. Wilking,31 S. Chen,32 Y. Zhang,32 K. Connolly,33 and R. J. Wilkes33
(The Super-Kamiokande Collaboration)
1
Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo, Kamioka, Gifu 506-1205, Japan
2
Research Center for Cosmic Neutrinos, Institute for Cosmic Ray
Research, University of Tokyo, Kashiwa, Chiba 277-8582, Japan
3
Department of Theoretical Physics, University Autonoma Madrid, 28049 Madrid, Spain
4
Department of Physics, Boston University, Boston, MA 02215, USA
5
Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T1Z4, Canada
6
Physics Department, Brookhaven National Laboratory, Upton, NY 11973, USA
7
Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697-4575, USA
8
Department of Physics, California State University, Dominguez Hills, Carson, CA 90747, USA
9
Department of Physics, Chonnam National University, Kwangju 500-757, Korea
10
Department of Physics, Duke University, Durham NC 27708, USA
11
Junior College, Fukuoka Institute of Technology, Fukuoka, Fukuoka 811-0295, Japan
12
Department of Physics, Gifu University, Gifu, Gifu 501-1193, Japan
13
GIST College, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
14
Department of Physics and Astronomy, University of Hawaii, Honolulu, HI 96822, USA
15
High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
16
Department of Physics, Kobe University, Kobe, Hyogo 657-8501, Japan
17
Department of Physics, Kyoto University, Kyoto, Kyoto 606-8502, Japan
18
Department of Physics, Miyagi University of Education, Sendai, Miyagi 980-0845, Japan
19
Solar Terrestrial Environment Laboratory, Nagoya University, Nagoya, Aichi 464-8602, Japan
20
Department of Physics and Astronomy, State University of New York at Stony Brook, NY 11794-3800, USA
21
Department of Physics, Okayama University, Okayama, Okayama 700-8530, Japan
22
Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
23
Department of Physics, University of Regina, 3737 Wascana Parkway, Regina, SK, S4SOA2, Canada
24
Department of Physics, Seoul National University, Seoul 151-742, Korea
25
Department of Informatics in Social Welfare, Shizuoka University of Welfare, Yaizu, Shizuoka, 425-8611, Japan
26
Department of Physics, Sungkyunkwan University, Suwon 440-746, Korea
27
Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan
28
The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
29
Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai
Institutes for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8582, Japan
30
Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S1A7, Canada
31
TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T2A3, Canada
32
Department of Engineering Physics, Tsinghua University, Beijing, 100084, China
33
Department of Physics, University of Washington, Seattle, WA 98195-1560, USA
34
National Centre For Nuclear Research, 00-681 Warsaw, Poland
(Dated: October 17, 2014)
A search for neutrino oscillations induced by Lorentz violation has been performed using 4,438
live-days of Super-Kamiokande atmospheric neutrino data. The Lorentz violation is included in
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP/2014-241
2014/10/17
CMS-JME-13-006
arXiv:1410.4227v1 [hep-ex] 15 Oct 2014
Identification techniques for highly boosted W bosons that
decay into hadrons
The CMS Collaboration∗
Abstract
In searches for new physics in the energy regime of the LHC, it is becoming increasingly important to distinguish single-jet objects that originate from the merging of the
decay products of W bosons produced with high transverse momenta from jets initiated by single partons. Algorithms are defined to identify such W jets for different
signals of interest, using techniques that are also applicable to other decays of bosons
to hadrons that result in a single jet, such as those from highly boosted Z and Higgs
bosons. The efficiency for tagging W jets is measured in data collected with the CMS
detector at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb−1 . The performance of W tagging in data is compared with predictions
from several Monte Carlo simulators.
Submitted to the Journal of High Energy Physics
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:1410.4481v1 [gr-qc] 16 Oct 2014
A Black-Hole Primer:
Particles, Waves,
Critical Phenomena and
Superradiant Instabilities
Bad Honnef School “GR@99”
Emanuele Berti
(14 October 2014)
Contents
1 Introduction
1.1 Newtonian Black Holes?
1.2 The Schwarzschild and Kerr Metrics
3
4
6
2 Particles
2.1 Geodesic Equations from a Variational Principle
2.2 Geodesics in Static, Spherically Symmetric Spacetimes
2.3 Schwarzschild Black Holes
2.3.1 Circular Geodesics in the Schwarzschild Metric
2.3.2 The Critical Impact Parameter
2.4 Order and Chaos in Geodesic Motion
2.4.1 Lyapunov Exponents for Circular Orbits in Static, Spherically
Symmetric Spacetimes
7
7
8
10
10
11
13
3 Waves
3.1 Massive Scalar Fields in a Spherically Symmetric Spacetime
3.2 Solution of the Scattering Problem
3.2.1 Leaver’s Solution
3.2.2 The WKB Approximation
3.3 Geodesic Stability and Black-Hole Quasinormal Modes
3.4 Superradiant Amplification
3.4.1 Massive Scalar Fields in the Kerr Metric
17
17
20
21
24
27
28
30
14
4 The Unreasonable Power of Perturbation Theory: Two Examples 33
4.1 Critical Phenomena in Binary Mergers
33
4.1.1 Extreme Mass-Ratio Binaries
33
4.1.2 Comparable-Mass Binaries
37
4.2 Black-Hole Bombs
39
1
arXiv:1410.4404v1 [astro-ph.HE] 16 Oct 2014
A fresh look on the limit
on ultralight axion-like particles from SN1987A
Alexandre Payez
Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany
DOI: will be assigned
We revisit the limit on very light axion-like particles (ALPs) from the absence of gamma
rays coincidental with the neutrino burst from SN1987A. We use updated supernova simulations, modern models for the magnetic field inside the Galaxy, and a Primakoff cross
section which takes into account proton-degeneracy and mass-reduction effects.
We finally give an updated exclusion plot for the electromagnetic coupling of sub-eV ALPs,
comparing our new bound with other limits as well as with future ALP searches.
1
Reminder
Axion-like particles (ALPs) are generic predictions of theories beyond the Standard Model
of particle physics, where they essentially arise as pseudo-Nambu–Goldstone bosons of new
spontaneously broken global symmetries. The case for such light particles is actually arguably
getting even more interesting since the LHC discovered the scalar Higgs boson—and gave an
experimental evidence of how important spontaneous symmetry breaking can be in particle
physics— but has however so far found no new heavy particle beyond the Standard Model,
and in particular no signs of SUSY where it was presumably expected.
Together with the long-sought QCD axion, there is also some interest for ultralight ALPs,
somewhat driven by phenomenology: indeed, a number of observations in astrophysics have
been claimed by various authors to hint at the existence of such nearly massless (pseudo)scalars,
thereby defining another window of interest in the ALP parameter space. The reason why they
would be so interesting is the electromagnetic coupling that they might have, that would affect
in a number of ways the signals expected from astrophysical sources [1]. There of course exist
strong constraints on the electromagnetic coupling of such light particles, and the aim of this
work [2] is actually to revisit and update what has remained for almost 20 years the most
stringent bound over a wide range of masses in the astrophysical window [3, 4].
When a very massive star undergoes a core-collapse, lots of neutrinos are quickly radiated
by the proto-neutron star, leading to a short and intense neutrino burst that will arrive at Earth
hours before the optical flash. Such supernova (SN) explosions are in fact also an ideal place
to search for extremely light (ma . 10−9 eV) ALPs a with a generic two-photon interaction, of
effective coupling gaγ :
Laγγ =
Patras 2014
1
gaγ Fµν F˜ µν a.
4
(1)
1
arXiv:1410.4394v1 [hep-lat] 16 Oct 2014
London penetration depth and coherence length of
SU(3) vacuum flux tubes
Paolo Cea
Dipartimento di Fisica dell’Università di Bari
and INFN - Sezione di Bari, I-70126 Bari, Italy
E-mail: [email protected]
Leonardo Cosmai
INFN - Sezione di Bari, I-70126 Bari, Italy
E-mail: [email protected]
Francesca Cuteri∗
Dipartimento di Fisica dell’Università della Calabria
and INFN - Gruppo collegato di Cosenza, I-87036 Arcavacata di Rende, Cosenza, Italy
E-mail: [email protected]
Alessandro Papa
Dipartimento di Fisica dell’Università della Calabria
and INFN - Gruppo collegato di Cosenza, I-87036 Arcavacata di Rende, Cosenza, Italy
E-mail: [email protected]
The transverse profile of the chromoelectric field generated by a quark- antiquark pair in the
SU(3) vacuum is analysed within the dual superconductor scenario, then the London penetration
depth and coherence length are extracted. The color field is determined on the lattice through a
connected correlator of two Polyakov loops measured on smeared configurations.
The 32nd International Symposium on Lattice Field Theory,
23-28 June, 2014
Columbia University New York, NY
∗ Speaker.
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
http://pos.sissa.it/
Francesca Cuteri
London penetration depth and coherence length of SU(3) vacuum flux tubes
1. Introduction
As is well known, the chromoelectric flux tubes produced by a pair of static color charges in the
QCD vacuum represent an evidence for the confinement phenomenon [1]. Monte Carlo simulations
of lattice QCD [2–4] allow nonperturbative studies of the chromoelectric field distribution associated with the flux-tube structures. Within the dual superconductor model of QCD vacuum, conjectured by ’t Hooft and Mandelstam [5], the condensation of color magnetic monopoles responsible
for the formation of flux tubes is seen in analogy to the formation of Cooper pairs in the BCS
theory of superconductivity. Whereas the dynamical condensation of color magnetic monopoles is
not explained by the dual superconductor construction, convincing lattice evidences for this condensation mechanism have been found [6]. In previous studies [4, 7], the flux-tube chromoelectric
field distribution has been investigated through the connected correlation function [3, 8]:
tr W LUP L†
1 htr(UP )tr(W )i
−
,
(1.1)
ρWconn =
htr(W )i
htr(W )i
N
where UP = Uµν (x) is the plaquette in the (µ, ν) plane, connected to the Wilson loop W by a
Schwinger line L, and N is the number of colors (see Fig. 1 in Refs. [7]). In the naive continuum
limit [3] we have
r
h
i
β conn
a→0
ρWconn −→ a2 g Fµν qq¯ − Fµν 0 ,
Fµν (x) =
ρ
(x) .
(1.2)
2N W
where h iqq¯ denotes the average in the presence of a static qq¯ pair and h i0 is the vacuum average.
In ordinary superconductivity tube-like structures arise as solutions of the Ginzburg-Landau
equations [9]. Within dual superconductivity, the formation of the chromoelectric flux tubes can
be interpreted as dual Meissner effect and the chromoelectric field distribution should resemble the
dual version of the Abrikosov vortex field distribution. This led to the proposal [4, 7] to fit the
transverse shape of the longitudinal chromoelectric field according to
Φ 2
µ K0 (µxt ) , xt > 0 ,
(1.3)
2π
where Kn is the modified Bessel function of order n, Φ is the external flux, and λ = 1/µ is the
London penetration length. However, Eq. (1.3) is valid only for type-II superconductors, i.e. for
λ ξ , ξ being the coherence length, which measures the coherence of the magnetic monopole
condensate. Several numerical studies [10] have, instead, shown that the confining vacuum behaves
much like a dual superconductor lying on the borderline between type-I and type-II superconductivity. Nonetheless, in Ref. [11] it has been suggested a different fitting function by exploiting the
results in Ref. [12]. There, from the assumption of a simple variational model for the magnitude of
the normalized order parameter of an isolated vortex, analytic expressions for magnetic field and
supercurrent density are derived, that solve the Ampere’s law and the Ginzburg-Landau equations.
By dual analogy
q
φ 1 K0 (R/λ )
El (xt ) =
,
R = xt2 + ξv2 ,
(1.4)
2π λ ξv K1 (ξv /λ )
where ξv is a variational core-radius parameter. Equation (1.4) is equivalent to
El (xt ) =
El (xt ) =
φ µ 2 K0 [(µ 2 xt2 + α 2 )1/2 ]
,
2π α
K1 [α]
2
µ=
1
,
λ
1
λ
= .
α
ξv
(1.5)
arXiv:1410.4333v1 [hep-lat] 16 Oct 2014
Hadron masses from fixed topology simulations:
parity partners and SU(2) Yang-Mills results
Arthur Dromard∗, Christopher Czaban, Marc Wagner
Goethe-Universität Frankfurt am Main
Institut für Theoretische Physik
Max-von-Laue-Straße 1, D-60438 Frankfurt am Main, Germany
E-mail: [email protected],
[email protected],
[email protected]
Lattice QCD simulations tend to get stuck in a single topological sector at fine lattice spacing,
or when using chirally symmetric quarks. In such cases computed observables differ from their
full QCD counterparts by finite size effects, which need to be understood on a quantitative level.
We discuss extensions of existing relations from the literature between correlation functions at
fixed topology and hadron masses at unfixed topology. Particular focus is put on disentangling
positive and negative parity states, which mix, when the topological charge is fixed. We also
present numerical results for SU(2) Yang-Mills Theory.
The 32nd International Symposium on Lattice Field Theory,
23-28 June, 2014
Columbia University New York, NY
∗ Speaker.
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
Hadron masses from fixed topology simulations
http://pos.sissa.it/
Arthur Dromard
1. Introduction
Topology freezing or fixing are important issues in quantum field theory, in particular in QCD.
For example Monte Carlo simulations with a local update algorithm tend to be stuck in a single
topological sector at lattice spacings a . 0.05 fm, which are nowadays still rather fine, but realistic
[1]. Similarly, when simulating chirally symmetric overlap quarks, the corresponding algorithms
are not able to generate transitions between different topological sectors (cf. e.g. [2]).
In view of these issues it is important to develop methods, which allow us to obtain physically
meaningful results (i.e. results corresponding to unfixed topology) from fixed topology simulations.
The starting point for our work are the seminal papers [3, 4]. The calculations from these papers
have been extended in [5, 6] by including fixed topology correction terms up to O(1/V 3 ). Tests and
applications of these equations to quantum mechanics, 2d O(3) model and the Schwinger model
can be found in [7, 8, 9, 10, 5, 11, 6, 12]. Here we discuss parity mixing due to topology fixing
and its consequences, when extracting hadron masses from fixed topology simulations. We also
present results on SU(2) Yang-Mills theory.
2. BCNW equation and extensions
2.1 BCNW equation and extraction of hadron masses from fixed topology simulations
The partition function and the two-point correlation function of a hadron creation operator O
at fixed topological charge Q and finite spacetime volume V are
ˆ
ZQ,V = DA Dψ Dψ¯ δQ,Q[A] e−SE [A,ψ¯ ,ψ ]
ˆ
(2.1)
1
DA Dψ Dψ¯ δQ,Q[A] O† (t)O(0)e−SE [A,ψ¯ ,ψ ] .
CQ,V (t) =
ZQ,V
For large V one can use a saddle point approximation and expand the correlation function [3],
(2)
M (0)t
1
Q2
,
(2.2)
CQ,V (t) = α (0) exp − MH (0)t − H
1−
+O
2χt V
χt V
χt2V 2
where α (0) = α (θ = 0) is a constant, MH (0) = MH (θ = 0) the physical hadron mass (i.e. at
unfixed topology), θ denotes the QCD vacuum angle and χt the topological susceptibility. In the
following we will refer to this equation as BCNW equation1 . In order to be a valid approximation,
(2)
certain conditions have to be fulfilled, e.g. 1/χt V ≪ 1, |Q|/χt V ≪ 1 and |MH (0)t|/χt V ≪ 1. For
a detailed discussion cf. [6], Section 4.
A straightforward method to determine physical hadron masses (i.e. at unfixed topology) from
fixed topology simulations based on the BCNW equation has been proposed in [3]:
1. Perform simulations at fixed topology for different topological charges Q and spacetime
volumes V , for which the BCNW equation is a good approximation, i.e. where the above
mentioned conditions are fulfilled. Compute CQ,V (t) for each simulation.
(2)
2. Determine the physical hadron mass MH (0), MH (0) and χt by fitting the BCNW equation
(2.2) to the numerical results for CQ,V (t) obtained in step 1.
1 BCNW
stands for R. Brower, S. Chandrasekharan, J. W. Negele and U.-J. Wiese
2
Dilepton Production in Transport-based Approaches
Janus Weil1 , Stephan Endres1 , Hendrik van Hees1 , Marcus Bleicher1 , Ulrich Mosel2
1
arXiv:1410.4206v1 [nucl-th] 15 Oct 2014
2
Frankfurt Institute for Advanced Studies , Ruth-Moufang-Str. 1, 60438 Frankfurt, Germany
Institut f¨
ur Theoretische Physik, JLU Giessen, Heinrich-Buff-Ring 16, 35392 Giessen, Germany
DOI: will be assigned
We investigate dilepton production in transport-based approaches and show that the
baryon couplings of the ρ meson represent the most important ingredient for understanding the measured dilepton spectra. At low energies (of a few GeV), the baryon resonances
naturally play a larger role and affect already the vacuum spectra via Dalitz-like contributions, which can be captured well in an on-shell-transport scheme. At higher energies,
the baryons mostly affect the in-medium self energy of the ρ, which is harder to tackle in
transport models and requires advanced techniques.
1
Introduction
Lepton pairs are known to be an ideal probe for studying phenomena at high densities and
temperatures. They are created at all stages of a heavy-ion collision, but unlike hadrons they
can escape the hot and dense zone almost undisturbed (since they only interact electromagnetically) and thus can carry genuine in-medium information out to the detector. Dileptons are
particularly well-suited to study the in-medium properties of vector mesons, since the latter can
directly convert into a virtual photon, and thus a lepton pair [1, 2]. One of the groundbreaking
experiments in this field was NA60 at the CERN SPS, which revealed that the ρ spectral function is strongly broadened in the medium. Calculations by Rapp et al. have shown that this
collisional broadening is mostly driven by baryonic effects, i.e., the coupling of the ρ meson to
baryon resonances (N ∗ , ∆∗ ) [3]. In the low-energy regime, the data taken by the DLS detector
have puzzled theorists for years and have recently been confirmed and extended by new measurements by the HADES collaboration [4, 5, 6, 7, 8, 9]. At such low energies, it is expected
that not only the in-medium properties are determined by baryonic effects, but that already
the production mechanism of vector mesons is dominated by the coupling to baryons (even in
vacuum).
2
The model: hadronic transport + VMD
Already our previous investigations [10] based on the GiBUU transport model [11] have shown
that the baryonic N ∗ and ∆∗ resonances can give important contributions to dilepton spectra
at SIS energies, both from pp and AA collisions, via Dalitz-like contributions. This finding
was based on the assumption that these resonances decay into a lepton pair exclusively via an
intermediate ρ meson (i.e. strict vector-meson dominance). In the transport simulation, the
Dalitz decays R → e+ e− N are treated as a two-step process, where the first part is an R → ρN
PANIC14
1
DESY 14-180
FTPI-MINN-14/37
IPMU14-0320
arXiv:1410.4549v1 [hep-ph] 16 Oct 2014
Higgsino Dark Matter in High-Scale Supersymmetry
Natsumi Nagata1 and Satoshi Shirai2
1
William I. Fine Theoretical Physics Institute, School of Physics and Astronomy,
University of Minnesota, Minneapolis, MN 55455, USA,
and Kavli Institute for the Physics and Mathematics of the Universe (WPI),
Todai Institutes for Advanced Study, University of Tokyo, Kashiwa 277-8583, Japan
2
Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg, Germany
Abstract
We study a supersymmetric (SUSY) Standard Model in which a Higgsino is light enough
to be dark matter, while the other SUSY particles are much heavier than the weak scale. We
carefully treat the effects of heavy SUSY particles to the Higgsino nature, especially taking
into account the renormalization effects due to the large hierarchy between the Higgsino and
the SUSY breaking scales. Inelastic scattering of the Higgsino dark matter with a nucleus is
studied, and the constraints on the scattering by the direct detection experiments are discussed.
This gives an upper limit on the new physics scale. Bounds on the dark matter-nucleon elastic
scattering, the electric dipole moments, and direct production of Higgsinos, on the other hand,
give a lower limit. We show the current status on the limits and discuss the future prospects.
CERN-PH-TH/2014-198, MITP/14-078
arXiv:1410.4545v1 [hep-ph] 16 Oct 2014
Global fits to b → s`` data and signs for
lepton non–universality
T. Hurth∗,a , F. Mahmoudi†,b,c , S. Neshatpour‡,d
a PRISMA
Cluster of Excellence and Institute for Physics (THEP)
Johannes Gutenberg University, D-55099 Mainz, Germany
b Universit´
e
de Lyon, Universit´e Lyon 1, F-69622 Villeurbanne Cedex, France;
Centre de Recherche Astrophysique de Lyon, Saint-Genis Laval Cedex, F-69561, France;
CNRS, UMR 5574; Ecole Normale Sup´erieure de Lyon, France
c Theory
d School
Division, CERN, CH-1211 Geneva 23, Switzerland
of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM)
P.O. Box 19395-5531, Tehran, Iran
ABSTRACT
There are some slight tensions with the SM predictions within the latest LHCb measurements. Besides the known anomaly in one angular observable of the rare decay B → K ∗ µ+ µ− ,
another slight discrepancy recently occurred. The ratio RK = BR(B + → K + µ+ µ− )/BR(B + →
K + e+ e− ) in the low-q 2 region has been measured by LHCb showing a 2.6σ deviation from the
SM prediction. In contrast to the anomaly in the rare decay B → K ∗ µ+ µ− which is affected
by power corrections, the ratio RK is theoretically rather clean. We analyse all the b → s``
data with global fits and in particular explore the possibility of breaking of lepton universality.
Possible cross-checks with an analysis of the inclusive B → Xs `+ `− decay are also explored.
∗
Email: [email protected]
Also Institut Universitaire de France, 103 boulevard Saint-Michel, 75005 Paris, France, Email: [email protected]
‡
Email:[email protected]
†
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
TMDs: Evolution, modeling, precision
Umberto D’Alesio,1 , a , Miguel G. Echevarría,2 , b , Stefano Melis3 , c , and Ignazio Scimemi3 , d
arXiv:1410.4522v1 [hep-ph] 16 Oct 2014
1
Dipartimento di Fisica, Università di Cagliari, and INFN, Sezione di Cagliari, Cittadella Universitaria di Monserrato, I-09042
Monserrato (CA), Italy
2
NIKHEF and Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, NL-1081 HV Amsterdam,
the Netherlands
3
Dipartimento di Fisica, Università di Torino, Via P. Giuria 1, I-10125 Torino, Italy
4
Departamento de Física Teórica II, Universidad Complutense de Madrid, 28040 Madrid, Spain
Abstract. The factorization theorem for qT spectra in Drell-Yan processes, boson production and semi-inclusive
deep inelastic scattering allows for the determination of the non-perturbative parts of transverse momentum
dependent parton distribution functions. Here we discuss the fit of Drell-Yan and Z-production data using
the transverse momentum dependent formalism and the resummation of the evolution kernel. We find a good
theoretical stability of the results and a final χ2 /points . 1. We show how the fixing of the non-perturbative
pieces of the evolution can be used to make predictions at present and future colliders.
1 Introduction
The study of differential cross sections is notoriously a
great source of information on the nature of fundamental interactions. Recently the factorization theorem for
transverse momentum dependent cross sections formulated by two groups [1–4] has pointed out that in DrellYan (DY), semi-inclusive deep inelastic scattering (SIDIS)
and e+ e− → 2 hadrons/jets at high boson invariant mass,
all non-perturbative QCD effects can be encoded in the so
called Transverse Momentum Distributions (TMDs) and
can be included in experiments run at different energies
solving appropriate evolution equations. The evolution
factors so derived are fixed by perturbative QCD only up
to a certain level of accuracy, depending, among the others, on the initial and final center of mass energy scales.
The fundamental issue behind the evolution between two
scales of the TMDs is that the factorization theorem is
valid in both energy regimes.
The object of this talk concerns the study of TMD for
initial states, the so called transverse momentum dependent parton distribution functions (TMDPDFs). As a first
we want to study up to which level the evolution of TMDPDF can be fixed just using resummations of the perturbative series using the data of Drell-Yan and vector-boson
production at hadron colliders currently available. This
analysis illustrates some important points when comparing
to other attempts to include non-perturbative QCD effects
in differential cross sections, like in Ref. [5–8], and the use
of non-perturbative models. Finally we show the precision
a e-mail: [email protected]
b e-mail: [email protected]
c e-mail: [email protected]
d Speaker, e-mail: [email protected]
that can be achieved making predictions for some observables at the Large Hadron Collider (LHC). In particular we
study the differential cross section for Z-boson production
at the peak of the distribution.
The cross sections that we consider in this work can
be formulated schematically according to the factorization
formula [1, 2, 4]
Z
dσ
2 2
∼ H(Q , µ ) d2 kAT d2 kBT δ(2) (kAT + kBT − qT )
dqT
× F A (xA , kAT ; ζA , µ) F B (xB , kBT ; ζB , µ) ,
(1)
where F A,B are the TMDPDFs. They depend on the dilepton invariant mass trough the scales ζA and ζB 1 , being
ζA ζB = Q4 , the intrinsic parton transverse momenta, the
factorization scale µ and the lightcone momentum fractions. Finally, H is the hard factor, which is spin independent and can be calculated adopting the standard perturbation theory.
2 Construction of TMDPDF
The construction of the TMDPDF which are part of the
cross section follows several steps, which can be found in
Ref. [9] and we partially report here.
Parametrizing the non-perturbative large-bT region of
the quark TMDPDF (similar expressions hold for the
gluon TMDPDF), we write it at some initial scale Qi as
pert
NP
F˜ q/N (x, bT ; Q2i , µi ) = F˜ q/N (x, bT ; Q2i , µi ) F˜ q/N
(x, bT ; Qi ) ,
(2)
1 In Ref. [2, 3] the authors used the equivalent notation ζ = Q2 /α
A
and ζB = Q2 α, where α is the soft function splitting parameter.
The Journal’s name will be set by the publisher
DOI: will be set by the publisher
c Owned by the authors, published by EDP Sciences, 2014
Status of DVMP, DVCS and GPDs
P. Kroll1, a
Abstract. The analysis of exclusive meson leptoproduction (DVMP) within the handbag approach is reviewed
and the parametrization of the generalized parton distributions (GPDs) is discussed in some detail with the main
interest focused of the GPDs H and E. Applications of the GPDs extracted from DVMP to other hard exclusive
processes as for instance deeply virtual Compton scattering (DVCS) and an evaluation of Ji’s sum rule are also
presented.
103
1 Introduction
xB ≃ 0.002
H1(09)
bc
The handbag approach to hard exclusive leptoproduction
of photons and mesons off protons has extensively been
studied during the last fifteen years. It turned out that the
handbag approach allows for a detailed analysis of cross
sections, asymmetries and spin density matrix elements
(SDME) for these processes. The handbag approach is
based on factorization of the process amplitudes in a hard
subprocess, e.g. γ∗ q → γ(M)q, and soft hadronic matrix
elements parametrized in terms of GPDs. This factorization property has been shown to hold rigorously in the
collinear limit for large photon virtuality, Q, and large energy, W, but fixed Bjorken-x, xB [1, 2]. However, power
corrections to these asymptotic results are not under control. It is therefore unclear at which values of Q2 and W the
asymptotic results apply. In fact, there are strong effects in
meson leptoproduction which are not in accord with the
asymptotic predictions. Thus, for instance, the contribution from longitudinally polarized virtual photons to likewise polarized vector (or pseudosalar) mesons transitions
(γ∗L → VL (P)) dominate asymptotically; the ratio of the
longitudinal and transverse cross sections (R = σL /σT )
grows proportionally to Q2 . Experimentally [3], R for ρ0
2
production only amounts to about 2 for Q 2 <
∼ 10 GeV , i.e.
contributions from transversely polarized photons are not
small. For ω production transverse photons even dominate
2
2<
[4], R(ω) is only about 0.3 for 2 GeV2 <
∼ Q ∼ 4 GeV . For
0
π production transverse photons probably dominate as
well [5]. The amplitudes for γ∗L → ρ0L transitions do also
not plainly agree with the asymptotic picture which predicts the scaling law σL ∝ 1/Q 6 (modulo powers of ln Q 2
from evolution and the running of α s ) at fixed Bjorkenx. As can be seen from Fig. 1 the data 1 for the ρ0 cross
4
section [3] rather fall as <
of cor∼ 1/Q . Another example
rections to the asymptotic results for the γ∗L → VL (P) ama e-mail: [email protected]
1 Since
R is slightly increasing with Q 2 σL is even flatter than 1/Q 4 .
σ(γ ∗p → ρ0p) [nb]
arXiv:1410.4450v1 [hep-ph] 16 Oct 2014
1
Fachbereich Physik, Universität Wuppertal, 42097 Wuppertal, Germany and Institute für Theoretische Physik, Universität Regensburg, 93040 Regensburg, Germany
102
bc
bc
101
∼ 1/Q3.92
bc
bc
100
2
5
10
Q2[GeV2]
20
30
Figure 1. The cross section for ρ0 electroproduction versus Q2
at xB ≃ 0.002. Data are taken from [3] and compared to a powerlaw fit.
plitudes is set by the strong contributions from the pion
pole to π+ production that has been observed experimentally [6, 7]. In this talk I am going to report on an extraction of the GPDs from DVMP [5, 8–10]. In this analysis the GPDs are constructed from double distributions
(DDs)[11, 12] and the partonic subprocesses are computed
within the modified perturbative approach in which quark
transverse degrees of freedom as well as Sudakov suppression [13] are taken into account in order to model
power corrections. As explained above these corrections
are needed for instance in order to change the asymptotic
1/Q 6 fall of the longitudinal ρ0 cross section in an effective 1/Q 4 behavior. The emission and re-absorption of the
partons by the protons are treated collinearly to the proton
momenta in [5, 8–10]. From the analyses of the longitudinal cross sections for ρ0 and φ production the GPD H
has been extracted [8]. The transverse target spin asymmetries for ρ0 production provide information on the GPD
E. Generalizations of the handbag approach to γT∗ → VT
and γT∗ → VL (P) transitions allow for a study of further
e E,
e HT , E¯ T ). The extracted set of GPDs are subGPDs (H,
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–3
Light neutrino mass spectrum with one or two right-handed singlet fermions
added
Darius Jurˇciukonisa , Thomas Gajdosikb , Andrius Juodagalvisa
arXiv:1410.4443v1 [hep-ph] 16 Oct 2014
a Vilnius
University, Institute of Theoretical Physics and Astronomy, A. Goˇstauto st. 12, LT-01108 Vilnius, Lithuania
b Vilnius University, Physics Faculty, Saul˙
etekio al. 9, LT-10222 Vilnius, Lithuania
Abstract
We analyse two cases of the minimal extension of the Standard Model when one or two right-handed fields are
added to the three left-handed fields. A second Higgs doublet (two Higgs doublet model – 2HDM) is included in
our model. We calculate one-loop radiative corrections to the mass parameters which produce mass terms for the
neutral leptons. In both cases we numerically analyse light neutrino masses as functions of the heavy neutrino masses.
Parameters of the model are varied to find light neutrino masses that are compatible with experimental data of solar
∆m2 and atmospheric ∆m2atm neutrino mass differences for normal hierarchy. We choose values for the parameters of
the tree-level by numerical scans, where we look for the best agreement between computed and experimental neutrino
oscillation angles.
Keywords:
Neutrino, seesaw mechanism, Higgs doublet
1. Description of the model
The mass terms for the neutrinos can be written in a
compact form as a mass term with a (nL + nR ) × (nL + nR )
symmetric mass matrix
!
0
MDT
Mν =
(1)
ˆR ,
MD M
where MD is a nL ×nR Dirac neutrino mass matrix, while
ˆ R is a diagonal matrix. Mν can
the hat indicates that M
be diagonalized as
U T Mν U = m
ˆ = diag m1 , m2 , . . . , mnL +nR , (2)
where the mi are real and non-negative. In order to implement the seesaw mechanism [1] we assume that the
elements of MD are of order mD and those of MR are of
order mR , with mD mR . Then, the neutrino masses
mi with i = 1, 2, . . . , nL are of order m2D /mR , while those
with i = nL + 1, . . . , nL + nR are of order mR .
In the standard seesaw, one-loop corrections to the
mass matrix, i.e. the self energies, are determined by
the neutrino interactions with the Z boson, the neutral
Goldstone boson G0 , and the Higgs boson h0 . Each diagram contains a divergent piece but the sum of these
three contributions turns out to be finite.
Once the one-loop corrections are taken into account
the neutral fermion mass matrix is given by
!
!
δML
MDT + δMDT
δML MDT
(1)
Mν =
ˆ R + δMR ≈ MD M
ˆ R (3)
MD + δMD M
where the 03×3 matrix appearing at tree level (1) is replaced by the contribution δML . This correction is a
symmetric matrix, it has the largest influence as compared to other corrections.
The expression for one-loop corrections is given by
[2]

−1 

 m
  m
2
2 
X 1
 †
ˆ
ˆ



T ∗ 

 ln 

m
ˆ
∆
U
−
1
δML =
R
b
 m2 0
  m2 0  UR ∆b
32π2
b
+
Hb
2
3g
64π2 m2W
Hb
 2
−1  2 
 m
  m
ˆ
ˆ 
MDT UR∗ m
ˆ  2 − 1 ln  2  UR† MD , (4)
mZ
mZ
DESY Report 14-188
HERAFitter
arXiv:1410.4412v1 [hep-ph] 16 Oct 2014
Open Source QCD Fit Project
S. Alekhin1,2 · O. Behnke3 · P. Belov3,4 · S. Borroni3 · M. Botje5 · D. Britzger3 ·
S. Camarda3 · A.M. Cooper-Sarkar6 · K. Daum7,8 · C. Diaconu9 · J. Feltesse10 ·
A. Gizhko3 · A. Glazov3 · A. Guffanti11 · M. Guzzi3 · F. Hautmann12,13,14 ·
A. Jung15 · H. Jung3,16 · V. Kolesnikov17 · H. Kowalski3 · O. Kuprash3 ·
A. Kusina18 · S. Levonian3 · K. Lipka3 · B. Lobodzinski19 · K. Lohwasser1,3 ·
A. Luszczak20 · B. Malaescu21 · R. McNulty22 · V. Myronenko3 · S. NaumannEmme3 · K. Nowak3,6 · F. Olness18 · E. Perez23 · H. Pirumov3 · R. Plaˇcakyt˙e3 ·
K. Rabbertz24 · V. Radescu3 · R. Sadykov17 · G.P. Salam25,26 · A. Sapronov17 ·
A. Sch¨oning27 · T. Sch¨orner-Sadenius3 · S. Shushkevich3 · W. Slominski28 ·
H. Spiesberger29 · P. Starovoitov3 · M. Sutton30 · J. Tomaszewska31 · O. Turkot3 ·
A. Vargas3 · G. Watt32 · K. Wichmann3
1
Deutsches Elektronen-Synchrotron (DESY), Platanenallee 6,
D–15738 Zeuthen, Germany
2 Institute for High Energy Physics,142281 Protvino, Moscow region,
Russia
3 Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany
4 Current address: Department of Physics, St. Petersburg State University, Ulyanovskaya 1, 198504 St. Petersburg, Russia
5 Nikhef, Science Park, Amsterdam, the Netherlands
6 Department of Physics, University of Oxford, Oxford, United Kingdom
7 Fachbereich C, Universit¨
at Wuppertal, Wuppertal, Germany
8 Rechenzentrum, Universit¨
at Wuppertal, Wuppertal, Germany
9 Aix Marseille Universite, CNRS/IN2P3, CPPM UMR 7346, 13288
Marseille, France
10 CEA, DSM/Irfu, CE-Saclay, Gif-sur-Yvette, France
11 Niels Bohr International Academy and Discovery Center, Niels
Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100
Copenhagen, Denmark
12 School of Physics and Astronomy, University of Southampton, UK
13 Rutherford Appleton Laboratory, Chilton OX11 0QX, United Kingdom
14 Dept. of Theoretical Physics, University of Oxford, Oxford OX1
3NP, United Kingdom
15 FERMILAB, Batavia, IL, 60510, USA
16 Elementaire Deeltjes Fysica, Universiteit Antwerpen, B 2020
Antwerpen, Belgium
17 Joint Institute for Nuclear Research (JINR), Joliot-Curie 6, 141980,
Dubna, Moscow Region, Russia
18 Southern Methodist University, Dallas, Texas
19 Max Planck Institut F¨
ur Physik, Werner Heisenberg Institut,
F¨ohringer Ring 6, Mu¨nchen
20 T. Kosciuszko Cracow University of Technology
21 Laboratoire de Physique Nucl´
eaire et de Hautes Energies, UPMC
and Universit´e, Paris-Diderot and CNRS/IN2P3, Paris, France
22 University College Dublin, Dublin 4, Ireland
23 CERN, European Organization for Nuclear Research, Geneva,
Switzerland
24 Institut f¨
ur Experimentelle Kernphysik, Karlsruhe, Germany
Abstract HERAFitter is an open-source package that provides a framework for the determination of the parton distribution functions (PDFs) of the proton and for many different kinds of analyses in Quantum Chromodynamics (QCD).
It encodes results from a wide range of experimental measurements in lepton-proton deep inelastic scattering and
proton-proton (proton-antiproton) collisions at hadron colliders. These are complemented with a variety of theoretical
options for calculating PDF-dependent cross section predictions corresponding to the measurements. The framework
covers a large number of the existing methods and schemes
used for PDF determination. The data and theoretical predictions are brought together through numerous methodological options for carrying out PDF fits and plotting tools to
help visualise the results. While primarily based on the approach of collinear factorisation, HERAFitter also provides
facilities for fits of dipole models and transverse-momentum
25
CERN, PH-TH, CH-1211 Geneva 23, Switzerland
leave from LPTHE; CNRS UMR 7589; UPMC Univ. Paris 6; Paris
75252, France
27 Physikalisches Institut, Universit¨
at Heidelberg, Heidelberg, Germany
28 Jagiellonian University, Institute of Physics, Reymonta 4, PL-30059 Cracow, Poland
29 PRISMA Cluster of Excellence, Institut f¨
ur Physik (WA THEP),
Johannes-Gutenberg-Universit¨at, D-55099 Mainz, Germany
30 University of Sussex, Department of Physics and Astronomy, Sussex House, Brighton BN1 9RH, United Kingdom
31 Warsaw University of Technology, Faculty of Physics, Koszykowa
75, 00-662 Warsaw, Poland
32 Institute for Particle Physics Phenomenology, Durham University,
Durham, DH1 3LE, United Kingdom
26
EPJ Web of Conferences
arXiv:1410.4365v1 [hep-ph] 16 Oct 2014
c Owned by the authors, published by EDP Sciences, 2014
Loop functions in thermal QCD
Antonio Vairoa
1
Physik-Department, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany
Abstract. We discuss divergences of loop functions in thermal QCD and compute perturbatively the Polyakov loop, the Polyakov loop correlator and the cyclic Wilson loop.
We show how these functions get mixed under renormalization.
1 Thermal loop functions
Thermal loop functions are gauge invariant quantities that can be computed by lattice QCD and that
are relevant for the dynamics of static sources in a thermal bath at a temperature T [1] (for a review,
see [2]). We will focus on three loop functions.
The Polyakov loop average in a thermal ensemble at a temperature T is defined as
P(T )|R ≡
1
hTr LR i,
dR
where R is the color representation: dA = N 2 − 1, dF = N, N is the number of colors, and
!
Z 1/T
dτ A0 (x, τ) .
LR (x) = P exp ig
(1)
(2)
0
The operator P stands for the path ordering of the color matrices. A graphical representation is in
figure 1.
Figure 1. Polyakov loop.
The Polyakov loop correlator is defined as
Pc (r, T ) ≡
1
hTr L†F (0)Tr LF (r)i,
N2
where r is the spatial separation of the two loops. A graphical representation is in figure 2.
a e-mail: [email protected]
(3)
Nisho-3-2014
Axion Stars and Fast Radio Bursts
Aiichi Iwazaki
arXiv:1410.4323v1 [hep-ph] 16 Oct 2014
International Economics and Politics, Nishogakusha University,
6-16 3-bantyo Chiyoda Tokyo 102-8336, Japan.
(Dated: Oct. 16, 2014)
We show that fast radio bursts arise from collisions between axion stars and neutron stars. The
bursts are emitted in the atmosphere of the neutron stars. The observed frequencies
of the bursts
are given by the axion mass ma such as ma /2π ≃ 1.4 GHz ma /(6 × 10−6 eV) . From the event rate
∼ 10−3 per year in a galaxy, we can determine the mass ∼ 10−11 M⊙ of the axion stars. Using these
values we can explain short durations ( ∼ms ) and amount of radiation energies ( ∼ 1043 GeV ) of
the bursts.
PACS numbers: 98.70.-f, 98.70.Dk, 14.80.Va, 11.27.+d
Axion, Neutron Star, Fast Radio Burst
Fast Radio Bursts ( FRBs ) have recently been discovered[1–3] at around 1.4 GHz frequency. The durations of the
bursts are typically a few milliseconds. The origin of the bursts has been suggested to be extra-galactic owing to their
large dispersion measures. This suggests that the large amount of the energies ∼ 1046 GeV/s is produced at the radio
frequencies. The event rate of the burst is estimated to be ∼ 10−3 per year in a galaxy. Furthermore, no gamma ray
bursts associated with the bursts have been detected. To find progenitors of the bursts, several models[4] have been
proposed.
In the letter, we show that FRBs arise from collisions between neutron stars and axion stars[5, 6]. The axion star is
a boson star ( known as oscillaton[7] ) made of axions bounded gravitationally. The axion stars have been discussed[8]
to be formed in an epoch after the period of equal matter and radiation energy density.
The production mechanism of FRBs is shown in the following. Under strong magnetic fields of neutron stars,
axion stars generate oscillating electric fields[9]. When they collide with the neutron stars, the oscillating electric
fields rapidly produce radiations in the atmospheres of the neutron stars. Since the frequency of the oscillating
electric field is given by the axion mass ma , the frequency of the radiations produced[10] in the collisions is equal
to ma /2π ≃ 2.4 GHz (ma /10−5 eV). This is the case of electrons accelerated by the electric field initially stopping
relative to the axion stars. Actually, we need to take into account Doppler effect owing to the electron motions in the
atmosphere of the neutron stars, in order to explain finite band width of the observed FRBs.
The observations of FRBs constraint the parameters of the axion stars, that is, the mass of the axion and the mass
of the axion stars. The observed frequency ( ≃ 1.4 GHz ) of FRBs gives the mass ( ≃ 6 × 10−6eV ) of the axion, while
the observed rate of the bursts ( ∼ 10−3 per year in a galaxy ) gives the mass ( ∼ 10−11 M⊙ ) of the axion stars under
the assumption that halo of galaxy is composed of the axion stars. Then, with the use of the theoretical formula[6, 9]
relating radius Ra to mass Ma of the axion stars, we can find the radius Ra ∼ 160km. Since the relative velocity vc
at the time when the collisions occur is estimated to be a several ten thousand km/s, we find that the durations of
FRBs are given by Ra /vc ∼ a few milliseconds.
First we explain the classical solutions of the axion stars obtained in previous papers[6, 9–11]. The solutions are
found by solving classical equations of axion field a(~x, t) coupled with gravity. Assuming the axion potential such that
Va = −fa2 m2a cos(a/fa ) ≃ −fa2 m2a + m2a a2 /2 for a/fa ≪ 1, we approximately obtain spherical symmetric solutions,
a(~x, t) = a0 fa exp(−
r
) sin(ma t),
Ra
(1)
with r = |~x|, where ma and fa denote the mass and decay constant of the axion, respectively. The solutions represent
boson stars made of the axions bounded gravitationally, named as axion stars. The solutions are valid for the axion
stars with small masses Ma ≪ 10−5 M⊙ . The radius Ra of the axion stars is numerically given in terms of the mass
Ma by
Ra = 6.4
10−5 eV 2 10−11 M m2pl
⊙
,
≃
160
km
m2a Ma
ma
Ma
with the Planck mass mpl . The coefficient a0 is given by
(2)
Leading and higher twist contributions in semi-inclusive e+ e− annihilation at high energies
Shu-yi Wei,1 Kai-bao Chen,1 Yu-kun Song,2 and Zuo-tang Liang1
1
School of Physics & Key Laboratory of Particle Physics and Particle Irradiation (MOE),
Shandong University, Jinan, Shandong 250100, China
2
Interdisciplinary Center for Theoretical Study and Department of Modern Physics,
University of Science and Technology of China, Anhui 230026, China
arXiv:1410.4314v1 [hep-ph] 16 Oct 2014
By applying the collinear expansion, we construct a theoretical framework to describe the semi-inclusive
hadron production process e+ + e− → h + q(
¯ jet) + X at high energies where the leading and higher twist
contributions can be calculated systematically. With this framework, we calculate the contributions up to twist3 for spin-0, spin-1/2 and spin-1 hadrons respectively. We present the results for the hadronic tensors, the
differential cross sections, the azimuthal asymmetries, and the polarizations of the hadrons.
PACS numbers: 13.66.Bc, 13.87.Fh, 13.88.+e, 12.15.Ji, 12.38.-t, 12.39.St, 13.40.-f, 13.85.Ni
I.
INTRODUCTION
Since there is no hadron involved in the initial state, e+ e−
annihilation is most suitable for the study on fragmentation
functions among all different high energy reactions. Similar
to the study on parton distribution functions in deep-inelastic
lepton-nucleon scattering, the longitudinal momentum dependence can be studied in inclusive process while the transverse
momentum dependence can only be studied by going to semiinclusive processes.
The study on fragmentation functions is in parallel to that
on parton distribution and/or correlation functions in nucleon.
It plays an important role in the description of high energy
reactions and in studying the properties of hadronic interactions and is therefore a standing topic in the field of high energy physics. Many progresses have been made and summarized constantly in Review of Particle Properties [1] and also
other recent reviews [2]. Much attention has been attracted
recently in particular in the spin and transverse momentum
dependent (TMD) sessions both in theory [3–15], and in experiment [16–25]. This provides a new window to study the
fragmentation function, to test the hadronization models and
to learn the properties of Quantum Chromodynamics (QCD).
As stressed in different publications [26–28], to study the
spin and TMD sessions of the parton distribution or fragmentation function, higher twist contributions can be very significant. It is therefore very important for such studies in high
energy reactions to establish a suitable theoretical framework
where leading and higher twist contributions can be calculated
consistently. Collinear expansion seems to be the right technique for such a purpose.
Collinear expansion was developed in 1980s for inclusive
deep inelastic lepton-nucleon scattering [29, 30] and has been
known as the unique way to obtain a formalism where the
differential cross section including higher twist contributions
is expressed in terms of the calculable hard parts and gauge
invariant parton distribution and correlation functions. The
gauge links in the parton distributions are obtained automatically in the expansion procedure where multiple gluon scattering is taken into account.
Recently, the collinear expansion has been applied successfully to semi-inclusive deep inelastic lepton-nucleon scatter-
ing process l + N → l + q(jet) + X [31, 32], where q denotes a quark that corresponds to a jet in experiments. With
this process, TMD parton distribution and/or correlation functions can be studied. Calculations have been carried out
where leading and higher twist contributions and also nuclear
dependences have been obtained and expressed in terms of
the gauge invariant parton distribution and correlation functions [31–36].
To study the fragmentation function, we started with the inclusive hadron production process in e+ e− -annihilation at high
energies [14]. We have applied the collinear expansion to the
process and obtained a theoretical framework for describing
e+ + e− → h + X where leading and higher twist contributions
can be calculated systematically. With this process, the longitudinal momentum distribution of the fragmentation functions
can be studied and we have made calculations up to twist three
for hadrons with different spins respectively. Even in this
simple case, we have already obtained a number of interesting features such as the existence of transverse polarization at
twist-3 for spin-1/2 hadrons, the quark polarization independence of the leading twist spin alignment of vector mesons
and so on.
To study the TMD session of the fragmentation functions,
we need to go to semi-inclusive process where more than a
single hadron are detected. The simplest process in this case
is e+ +e− → h+q(jet)+X.
¯
In such semi-inclusive processes, the
measurable quantities sensitive to different components of the
fragmentation function are usually the azimuthal asymmetries
including both the spin dependent and the spin independent
ones. Higher twist effects can give significant contributions to
such asymmetries, hence a systematic calculation to pick up
the leading and higher twist contributions is important.
In this paper, we apply the collinear expansion to the semiinclusive process e+ + e− → h + q(jet)
¯
+ X. We derive the
theoretical framework suitable for the description of this process, and carry out the calculations up to twist 3 for hadrons
with different spins at the leading order in perturbative QCD.
We present the results for the hadronic tensors, the differential cross sections, the azimuthal asymmetries and the hadron
polarizations, and discuss the situation when confronting with
experiments. We shall note here that we can easily carry out
the same calculation for process e+ + e− → h + q(jet) + X, and
get similar results.
Relativistic corrections to static properties of the proton
D. Bedoya Fierro, N. G. Kelkar and M. Nowakowski
Departamento de Fisica, Universidad de los Andes,
Cra.1E No.18A-10, Santafe de Bogota, Colombia
arXiv:1410.4228v1 [hep-ph] 15 Oct 2014
Abstract
A new method to relate the proton electromagnetic form factors in momentum space to the
corresponding charge and magnetization densities with the inclusion of relativistic corrections is
presented by extending the standard Breit equation to higher orders in its 1/c2 expansion. Ap˜ E,M (q 2 ) in the Breit frame,
plying a Lorentz boost to the relativistically corrected form factors G
moments of the charge and magnetization distributions are evaluated. The proton charge radius
thus determined is found to be smaller and hence in better agreement with recent spectroscopy
results.
PACS numbers: 13.40.Gp, 14.20.Dh, 03.70.+k
1
October 17, 2014
arXiv:1410.4220v1 [hep-ph] 15 Oct 2014
Measurement of the Axial-Vector Coupling Constant gA in
Neutron Beta Decay
¨ rkisch1
Bastian Ma
Physikalisches Institut
Universit¨
at Heidelberg, Im Neuenheimer Feld 226, D-69120 Heidelberg, GERMANY
Hartmut Abele2
Atominstitut, Technische Universit¨at Wien, Stadionallee 2, 1020 Wien, AUSTRIA
The matrix element Vud of the CKM matrix can be determined by
two independent measurements in neutron decay: the neutron lifetime τn
and the ratio of coupling constants λ = gA /gV , which is most precisely
determined by measurements of the beta asymmetry angular correlation
coefficient A. We present recent progress on the determination of these
coupling constants.
PRESENTED AT
8th International Workshop on the CKM Unitarity Triangle
(CKM 2014),
Vienna, Austria,
September 8-12, 2014
1
Work supported by the Priority Programme SPP 1491 of the German Research Foundation (DFG) under contract MA4944/1.
2
Work supported by the Priority Programme SPP 1491 of the German Research Foundation (DFG) and by the Austrian FWF under contract I529-N20.
1
Introduction
To obtain the matrix element Vud from the decay of the free neutron only two separate
inputs are required. These are the neutron lifetime τn and the ratio of axial vector
and vector coupling constants λ = gA /gV , which can be determined by measurements
of angular correlations in neutron decay [1, 2]. Vud can then be determined by [3]
|Vud |2 =
(4908.7 ± 1.9)s
,
τn (1 + 3λ2 )
(1)
where the numerator includes all constants, with the Fermi coupling constant precisely
determined in muon decay, and the theoretical uncertainty of the radiative corrections
(see also Ref. [4]).
Assuming vector current conservation, the axial vector coupling constant can be
determined within the Standard Model from a variety of angular correlation measurements [1, 2]. The most precise determination comes from measurements of the beta
asymmetry A correlation coefficient, which describes the correlation between neutron
spin and electron momentum. To leading order A0 this asymmetry is given by
A0 =
−2 (λ2 − |λ|)
.
1 + 3λ2
(2)
Due to the equally high sensitivity on λ, the determination of the electron-neutrino
angular correlation a is another candidate. This work is an update of earlier presentations on the unitarity triangle [5, 6, 7, 8], the unitarity of the CKM matrix [9], and
other reviews [10, 11, 12, 13].
2
Recent Results
The most recent determinations of the beta asymmetry come from the UCNA Collaboration and the Perkeo II Collaboration. The decay of polarized neutrons in a
strong magnetic field is analysed by electron spectroscopy with a solid angle coverage
of 2 ×2π. In these experiments backscattering of electrons from the detectors [14, 15],
a serious source of error in β-spectroscopy, is strongly suppressed by a decrease in
magnetic field strength towards the detectors and detection of backscattered electrons
in the second 2π detector [16, 17, 18]. A backscatter suppression spectrometer is also
described in [19].
The UCNA Collaboration uses polarized ultracold neutrons at the Los Alamos
Neutron Science Center (LANSCE). Improvements in the experiment have led to
reductions in both statistical and systematic uncertainties. UCNs were polarized by
a 6 T prepolarizer magnet and a 7 T primary polarizer. The spin state is controlled
by an adiabatic fast passage spin flipper. Upstream of the prepolarizer magnet,
1
arXiv:1410.4216v1 [hep-ph] 15 Oct 2014
International Journal of Modern Physics: Conference Series
c The Authors
The Evolution of Soft Collinear Effective Theory
Christopher Lee
Theoretical Division, Los Alamos National Laboratory, MS B283
Los Alamos, NM 87544, USA
[email protected]
Received Day Month Year
Revised Day Month Year
Published Day Month Year
Soft Collinear Effective Theory (SCET) is an effective field theory of Quantum Chromodynamics (QCD) for processes where there are energetic, nearly lightlike degrees of
freedom interacting with one another via soft radiation. SCET has found many applications in high-energy and nuclear physics, especially in recent years the physics of hadronic
jets in e+ e− , lepton-hadron, hadron-hadron, and heavy-ion collisions. SCET can be used
to factorize multi-scale cross sections in these processes into single-scale hard, collinear,
and soft functions, and to evolve these through the renormalization group to resum large
logarithms of ratios of the scales that appear in the QCD perturbative expansion, as well
as to study properties of nonperturbative effects. We overview the elementary concepts
of SCET and describe how they can be applied in high-energy and nuclear physics.
Keywords: QCD, effective field theory, SCET, factorization, resummation, jets.
PACS numbers: 12.38.Cy, 12.39.St, 13.87.-a, 24.85.+p, 25.30.Fj, 25.75.Bh
1. Introduction
It is fair to say that effective field theory (EFT) has proven to be one of the most
powerful tools in modern physics.1, 2 By exploiting power expansions in small parameters determined by hierarchies of physical scales, EFTs help us make advances
in predictive power in controlled approximations that may be more difficult to
implement directly in the context of a full theory. In Quantum Chromodynamics (QCD), the development and application of Soft Collinear Effective Theory
(SCET)3, 4, 5, 6, 7, 8 in past decade-and-a-half has brought about such advances for
physical processes with energetic, nearly light-like degrees of freedom such as jets.
SCET has advanced our understanding of B physics and collider and jet physics in
vacuum and in heavy-ion collisions. These problems exhibit dependence on the hierarchically separated scales of a hard collision energy Q, on a transverse momentum
pT of collinear modes, of soft radiation with momentum ks , and of hadronization
This is an Open Access article published by World Scientific Publishing Company. It is distributed
under the terms of the Creative Commons Attribution 3.0 (CC-BY) License. Further distribution
of this work is permitted, provided the original work is properly cited.
1
Prepared for submission to JHEP
arXiv:1410.4203v1 [hep-ph] 15 Oct 2014
Low Mass Thermal Dilepton Production at NLO in a
Weakly Coupled Quark-Gluon Plasma
Jacopo Ghiglieri,1,2 Guy D. Moore1
1
2
McGill University, Department of Physics, 3600 rue University, Montreal QC H3A 2T8, Canada
Institute for Theoretical Physics, Albert Einstein Center, University of Bern, Sidlerstrasse 5, 3012
Bern, Switzerland
E-mail: [email protected], [email protected]
Abstract: We present a computation, within weakly-coupled thermal QCD, of the production rate of low invariant mass (M 2 ∼ g 2 T 2 ) dileptons, at next-to-leading order (NLO)
in the coupling (which is O(g 3 e2 T 2 )). This involves extending the NLO calculation of the
photon rate which we recently presented to the case of small nonzero photon invariant mass.
Numerical results are discussed and tabulated forms and code are provided for inclusion in
hydrodynamical models. We find that NLO corrections can increase the dilepton rate by
up to 30-40% relative to leading order. We find that the electromagnetic response of the
plasma for real photons and for small invariant mass but high energy dilepton pairs (e.g.,
M 2 < (300 MeV)2 but pT > 1 GeV) are close enough that dilepton pair measurements
really can serve as ersatz photon measurements. We also present a matching a la Ghisoiu
and Laine between our results and results at larger invariant masses.
Keywords: Dileptons, Hard Probes, Quark-Gluon Plasma, High order calculations
arXiv:1410.4193v1 [hep-ph] 15 Oct 2014
Extending the Standard Model Effective Field Theory
with the Complete Set of Dimension-7 Operators
Landon Lehman
Department of Physics
University of Notre Dame
Notre Dame, IN 46556
E-mail: [email protected]
Abstract: We present a complete list of the independent dimension-7 operators that are constructed using the Standard Model degrees of freedom and are invariant under the Standard Model
gauge group. This list contains only 20 independent operators; far fewer than the 63 operators available at dimension 6. All of these dimension-7 operators contain fermions and violate lepton number,
and 7 of the 20 violate baryon number as well. This result extends the Standard Model Effective
Field Theory (SMEFT) and allows a more detailed exploration of the structure and properties of
possible deformations from the Standard Model Lagrangian.
arXiv:1410.4356v1 [nucl-th] 16 Oct 2014
Recent development of complex scaling method
for many-body resonances and continua in light nuclei
Takayuki Myo,1,2 Yuma Kikuchi,3 Hiroshi Masui,4 Kiyoshi Kat¯o5
1
General Education, Faculty of Engineering, Osaka Institute of Technology,
Osaka 535-8585, Japan
2
Research Center for Nuclear Physics (RCNP), Osaka University,
Ibaraki 567-0047, Japan
3
Nishina Center for Accelerator-based Science, The Institute of
Physical and Chemical Research (RIKEN), Wako 351-0198, Japan
4
Information Processing Center, Kitami Institute of Technology,
Kitami 090-8507, Japan
5
Nuclear Reaction Data Centre, Faculty of Science, Hokkaido University,
Sapporo 060-0810, Japan
October 17, 2014
Abstract
The complex scaling method (CSM) is a useful similarity transformation of the Schr¨
odinger
equation, in which bound-state spectra are not changed but continuum spectra are separated
into resonant and non-resonant continuum ones. Because the asymptotic wave functions of the
separated resonant states are regularized by the CSM, many-body resonances can be obtained by
solving an eigenvalue problem with the L2 basis functions. Applying this method to a system
consisting of a core and valence nucleons, we investigate many-body resonant states in weakly
bound nuclei very far from the stability lines. Non-resonant continuum states are also obtained
with the discretized eigenvalues on the rotated branch cuts. Using these complex eigenvalues and
eigenstates in CSM, we construct the extended completeness relations and Green’s functions to
calculate strength functions and breakup cross sections. Various kinds of theoretical calculations
and comparisons with experimental data are presented.
Contents
1 Introduction
3
2 Unified treatments of bound, resonant and continuum states in CSM
2.1 Complex scaling method and the ABC theorem . . . . . . . . . . . . . . .
2.2 Three-body resonances . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Extended completeness relation in CSM . . . . . . . . . . . . . . . . . . .
2.4 Green’s function with CSM . . . . . . . . . . . . . . . . . . . . . . . . . .
1
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7
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9
10
12
arXiv:1410.2624v1 [physics.atom-ph] 9 Oct 2014
Spectroscopy of Ba and Ba+ deposits in solid xenon for barium tagging in
nEXO
B. Mong,1, 2 S. Cook,1, ∗ T. Walton,1 C. Chambers,1 A. Craycraft,1 C. Benitez-Medina,1, †
K. Hall,1, ‡ W. Fairbank Jr.,1, § J.B. Albert,3 D.J. Auty,4 P.S. Barbeau,5 V. Basque,6 D. Beck,7
M. Breidenbach,8 T. Brunner,9 G.F. Cao,10 B. Cleveland,2, ¶ M. Coon,7 T. Daniels,8 S.J. Daugherty,3
R. DeVoe,9 T. Didberidze,4 J. Dilling,11 M.J. Dolinski,12 M. Dunford,6 L. Fabris,13 J. Farine,2
W. Feldmeier,14 P. Fierlinger,14 D. Fudenberg,9 G. Giroux,15, ∗∗ R. Gornea,15 K. Graham,6
G. Gratta,9 M. Heffner,16 M. Hughes,4 X.S. Jiang,10 T.N. Johnson,3 S. Johnston,17 A. Karelin,18
L.J. Kaufman,3 R. Killick,6 T. Koffas,6 S. Kravitz,9 R. Kr¨
ucken,11 A. Kuchenkov,18 K.S. Kumar,19
20
6
12
7
D.S. Leonard, C. Licciardi, Y.H. Lin, J. Ling, R. MacLellan,21 M.G. Marino,14 D. Moore,9
A. Odian,8 I. Ostrovskiy,9 A. Piepke,4 A. Pocar,17 F. Retiere,11 P.C. Rowson,8 M.P. Rozo,6 A. Schubert,9
D. Sinclair,11, 6 E. Smith,12 V. Stekhanov,18 M. Tarka,7 T. Tolba,15 K. Twelker,9 J.-L. Vuilleumier,15
J. Walton,7 M. Weber,9 L.J. Wen,10 U. Wichoski,2 L. Yang,7 Y.-R. Yen,12 and Y.B. Zhao10
1
Physics Department, Colorado State University, Fort Collins CO, USA
2
Department of Physics, Laurentian University, Sudbury ON, Canada
3
Physics Department and CEEM, Indiana University, Bloomington IN, USA
4
Department of Physics and Astronomy, University of Alabama, Tuscaloosa AL, USA
5
Department of Physics, Duke University, and Triangle Universities
Nuclear Laboratory (TUNL), Durham North Carolina, USA
6
Physics Department, Carleton University, Ottawa ON, Canada
7
Physics Department, University of Illinois, Urbana-Champaign IL, USA
8
SLAC National Accelerator Laboratory, Stanford CA, USA
9
Physics Department, Stanford University, Stanford CA, USA
10
Institute of High Energy Physics, Beijing, China
11
TRIUMF, Vancouver BC, Canada
12
Department of Physics, Drexel University, Philadelphia PA, USA
13
Oak Ridge National Laboratory, Oak Ridge TN, USA
14
Technische Universitat Munchen, Physikdepartment and Excellence Cluster Universe, Garching, Germany
15
LHEP, Albert Einstein Center, University of Bern, Bern, Switzerland
16
Lawrence Livermore National Laboratory, Livermore CA, USA
17
Physics Department, University of Massachusetts, Amherst MA, USA
18
Institute for Theoretical and Experimental Physics, Moscow, Russia
19
Department of Physics and Astronomy, Stony Brook University, SUNY, Stony Brook NY,USA
20
Department of Physics, University of Seoul, Seoul, Korea
21
Department of Physics, University of South Dakota, Vermillion SD, USA
(Dated: October 13, 2014)
Progress on a method of barium tagging for the nEXO double beta decay experiment is reported.
Absorption and emission spectra for deposits of barium atoms and ions in solid xenon matrices are
presented. Excitation spectra for prominent emission lines, temperature dependence and bleaching
of the fluorescence reveal the existence of different matrix sites. A regular series of sharp lines
observed in Ba+ deposits is identified with some type of barium hydride molecule. Lower limits
for the fluorescence quantum efficiency of the principal Ba emission transition are reported. Under
current conditions, an image of ≤ 104 Ba atoms can be obtained. Prospects for imaging single Ba
atoms in solid xenon are discussed.
I.
∗
†
‡
§
¶
∗∗
Now at NIST, Boulder CO, USA
Now at Intel, Hillsboro OR, USA
Now at Raytheon, Denver CO, USA
Corresponding author
Also SNOLAB, Sudbury ON, Canada
Now at Queen’s University, Kingston ON, Canada
INTRODUCTION
The spectroscopy of atoms and molecules isolated
in solid matrices of inert gases dates back sixty years
[1]. Matrix isolation spectroscopy, as this method is
known, has established that atomic states in noble
gas matrices retain many of the fundamental proper-
Proton and Neutron Momentum Distributions in A = 3
Asymmetric Nuclei
A Hall A Collaboration Experiment
arXiv:1410.4451v1 [nucl-ex] 16 Oct 2014
Proposal PR12-13-012 to Jefferson Lab PAC 42, July 2014
C. Hyde, S.E. Kuhn and L.B. Weinstein (co-spokesperson)
Old Dominion University, Norfolk VA
M. Braverman, E. Cohen, O. Hen (co-spokesperson),
I. Korover, J. Lichtenstadt, E. Piasetzky, and I. Yaron
Tel-Aviv University, Tel Aviv, Israel
W. Boeglin (co-spokesperson), P. Markowitz and M. Sargsian
Florida International University, Miami, FL
W. Bertozzi, S. Gilad (co-spokesperson), and V. Sulkosky
Massachusetts Institute of Technology, Cambridge, MA
D.W. Higinbotham, C. Keppel, P. Solvignon and S.A. Wood
Thomas Jefferson National Accelerator Facility, Newport News, VA
Guy Ron
Hebrew University, Jerusalem, Israel
R. Gilman
Rutgers University, New Brunswick, NJ
J.W. Watson
Kent State University, Kent, OH
A. Beck and S. Maytal-Beck
Nuclear Research Center Negev, Beer-Sheva, Israel
ˇ
ˇ
J. Beriˇciˇc, M. Mihoviloviˇc, S. Sirca,
and S. Stajner
Joˇzef Stefan Institute, Ljubljana, Slovenia
D. Keller
University of Virginia, Charlottesville, VA
Vincenzo Bellini, Maria Concetta Sutera and Francesco Mammoliti
INFN/CT and University of Catania, Catania, Italy
J. Annand, D. Hamilton, and D. Ireland
University of Glasgow, Glasgow, United Kingdom
A. Sarty
St. Mary’s University, Halifax, Nova Scotia, Canada
L. Kaptari
Bogoliubov Lab. Theor. Phys., 141980, JINR, Dubna, Russia
C. Ciofi degli Atti
INFN Perugia, Perugia, Italy
(Dated: October 17, 2014)
arXiv:1410.4437v1 [nucl-ex] 16 Oct 2014
Measurement of inclusive jet spectra in pp, p–Pb,
and Pb–Pb collisions with the ALICE detector
R¨
udiger Haake for the ALICE Collaboration
Institut f¨
ur Kernphysik, Westf¨
alische Wilhelms-Universit¨
at M¨
unster, 48149 M¨
unster, Germany
E-mail: [email protected]
Abstract. Highly energetic jets are sensitive probes for the kinematic properties and the
topology of high energy hadron collisions. Jets are collimated sprays of charged and neutral
particles, which are produced in fragmentation of hard scattered partons from an early stage of
the collision. In ALICE, jets have been measured in pp, p–Pb, and Pb–Pb collisions at several
collision energies. While analyses of Pb–Pb events unveil properties of the hot and dense
medium formed in heavy-ion collisions, pp and p–Pb collisions can shed light on hadronization
and cold nuclear matter effects in jet production. Additionally, pp and p–Pb serve as a baseline
for disentangling hot and cold nuclear matter effects. A possible modification of the initial
state is tested in p–Pb analyses. For the extraction of a jet signal, the exact evaluation of
the background from the underlying event is an especially important ingredient. Due to the
different nature of underlying events, each collision system requires a different analysis technique
for removing the effect of the background on the jet sample. The focus of this publication is on
the ALICE measurements of nuclear modification factors connecting p–Pb and Pb–Pb events
to pp collisions. Furthermore, the radial jet structure is explored by comparing jet spectra
reconstructed with different resolution parameters.
1. Introduction
Jets can conceptually be described as the final state produced in a hard scattering. Therefore,
jets are an excellent tool to access a very early stage of the collision. The jet constituents represent the final state remnants of the fragmented and hadronized partons that were scattered
in the reaction. While all the detected particles have been created in a non-perturbative process (i.e. by hadronization), ideally, jets represent the kinematic properties of the originating
partons. Thus, jets are mainly determined by perturbative processes due to the high momentum transfer and the cross sections can be calculated with pQCD. This conceptual definition
is descriptive and very simple, the technical analysis of those objects is quite complicated though.
In pp collisions, jets can serve as a probe for undisturbed pQCD physics. In Pb–Pb collisions,
the medium effects like those from the quark-gluon plasma (QGP) can be probed. For p–Pb
collisions, formation of a hot, dense, and extended medium is not expected and therefore cold
nuclear matter effects, e.g. those described by nuclear parton distribution functions (nPDFs),
should be dominant.
Here, the focus is on the inclusive jet results currently available from the ALICE experiment.
Results and conclusions of recent ALICE measurements in pp, p–Pb, and Pb–Pb are presented in