Structural( biology( at( the( single( particle( level:( imaging( tobacco

Transcription

Structural( biology( at( the( single( particle( level:( imaging(
tobacco( mosaic( virus( by( low7energy( electron(
holography(
Jean%Nicolas, Longchamp*,, Tatiana, Latychevskaia,, Conrad, Escher,, &, Hans%Werner,
Fink,
Physics, Department,, University, of, Zurich,, Winterthurerstrasse, 190,, 8057, Zurich,,
Switzerland,
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*Corresponding(Author(
E#mail:[email protected]!
Keywords((
Graphene,!Freestanding,!Electron!microscopy,!Low#energy!electrons,!Holography,!
Tobacco!Mosaic!Virus,!Structural!Biology!
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Spectroscopy with cold and ultra-cold neutrons
Hartmut Abele,1, ∗ Tobias Jenke,1, † and Gertrud Konrad1, ‡
1
Atominstitut, Technische Universit¨
at Wien, Stadionallee 2, A-1020 Wien, Austria
(Dated: December 17, 2014)
We present two new types of spectroscopy methods for cold and ultra-cold neutrons. The first
method, which uses the R×B drift effect to disperse charged particles in a uniformly curved magnetic
field, allows to study neutron β-decay. We aim for a precision on the 10−4 level. The second method
that we refer to as gravity resonance spectroscopy (GRS) allows to test Newton’s gravity law at short
distances. At the level of precision we are able to provide constraints on any possible gravity-like
interaction. In particular, limits on dark energy chameleon fields are improved by several orders of
magnitude.
PACS numbers: 04.80.-y, 04.80.Cc, 14.80.Mz, 23.40.-s, 23.40.Bw
arXiv:1412.5011v1 [hep-ph] 16 Dec 2014
I.
INTRODUCTION
Neutrons react to all known forces and are a powerful tool for addressing fascinating questions in particle
physics, nuclear physics, and astronomy. It belongs to
the opportunities that the investigation of static and decay properties of the free neutron are key issues in particle
physics and astrophysics, which can be addressed complementary to the high-energy physics approach. Precision studies of Newton’s law at very small distances in
turn allow to probe for extra dimensions at the µm level
and can reveal the existence of new gauge bosons acting
within.
Precise symmetry tests of various kinds are coming
within reach with the proposed facility PERC [1, 2].
Projects using the PERC facility will test the Standard
Model at a much higher level of sensitivity benefiting
both, from the gain in statistical accuracy for individual
measurements and from the redundancy of observables
accessible. Neutron decay offers a number of independent
observables, considerably larger than the small number of
parameters describing this decay in the Standard Model.
Examples are the electron-antineutrino correlation coefficient a [3–6], the beta asymmetry parameter A [7–11], the
neutrino asymmetry parameter B [12, 13] (reconstructed
from proton and electron momenta), the proton asymmetry parameter C [14], the triple correlation coefficient
D [15, 16], the Fierz interference term b, and various correlation coefficients involving the electron spin [17, 18].
Each coefficient in turn relates to an underlying broken
symmetry. A method of loss-free spectroscopy is presented in Ref. [19].
In Sec. II, we present a novel spectroscopy technique
for electron and proton spectroscopy, which can be used
with PERC. In Sec. III, we present the first precision
measurements of gravitational quantum states with GRS.
∗ Electronic
address: [email protected]
‡ Electronic address: [email protected]
† Electronic
II.
NEUTRON β-DECAY AND R×B
SPECTROSCOPY
The facility PERC (Proton and Electron Radiation
Channel) [1], for high-precision measurements of neutron β-decay, is under development [2]. The basic idea of
PERC is to supply its users with an intense beam of welldefined electrons and protons (e−/p+ ) from free neutron
decay. The all-purpose e−/p+ -beam allows to measure a
variety of neutron decay observables related to physics in
and beyond the Standard Model [20–25].
Cold neutrons pass through the decay volume of PERC
where only a small fraction decays into charged e−/p+ and
neutral electron antineutrinos. The charged e−/p+ are
guided by the strong magnetic field of PERC towards
a user’s detection system. Figure 1 shows as an example the R×B drift spectrometer connected to the end of
PERC.
Detector
Last Coil of
PERC
Tilted Coils
y
x
e-/p+-beam
Aperture
z
FIG. 1: Scheme of the R×B drift spectrometer [26] connected to the end of PERC, with simulated e−/p+ -trajectories
in green.
High momentum resolution is provided by magnetic
spectrometers. The resolution ∆p = eB · ∆r for momen-
Eur. Phys. J. C manuscript No.
(will be inserted by the editor)
HOLMES
arXiv:1412.5060v1 [physics.ins-det] 16 Dec 2014
The Electron Capture Decay of
sub-eV sensitivity
163
Ho to Measure the Electron Neutrino Mass with
B. Alpert1 , M. Balata2 , D. Bennett1 , M. Biasotti3,4 , C. Boragno3,4 ,
C. Brofferio5,6 , V. Ceriale3,4 , D. Corsini3,4 , M. De Gerone3,4 , R. Dressler7 ,
M. Faverzani5,6 , E. Ferri5,6 , J. Fowler1 , F. Gatti3,4 , A. Giachero5,6 ,
J. Hays-Wehle1 , S. Heinitz7 , G. Hilton1 , U. K¨
oster9 , M. Lusignoli8,
5,6
1
2
5,6
M. Maino , J. Mates , S. Nisi , R. Nizzolo , A. Nucciottia,5,6 ,
G. Pessina6 , G. Pizzigoni3,4 , A. Puiu5,6 , S. Ragazzi5,6 , C. Reintsema1 ,
M. Ribeiro Gomes10 , D. Schmidt1 , D. Schumann7 , M. Sisti5,6 , D. Swetz1 ,
F. Terranova5,6 , J. Ullom1
1 National
Institute of Standards and Technology (NIST), Boulder, Colorado, USA
Laboratori Nazionali del Gran Sasso (LNGS), INFN, Assergi (AQ), Italy
3
Dipartimento di Fisica, Universit`
a di Genova, Genova, Italy
4
Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Genova, Genova, Italy
5
Dipartimento di Fisica, Universit`
a di Milano-Bicocca, Milano, Italy
6
Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Milano-Bicocca, Milano, Italy
7
Paul Scherrer Institut (PSI), Villigen, Switzerland
8
Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Roma 1, Roma, Italy
9
Institut Laue-Langevin (ILL), Grenoble, France
10
Multidisciplinary Centre for Astrophysics (CENTRA-IST), University of Lisbon, Lisbon, Portugal
Received: date / Revised version: date
2
Abstract The European Research Council has recently funded HOLMES, a new experiment to directly
measure the neutrino mass. HOLMES will perform a
calorimetric measurement of the energy released in the
decay of 163 Ho. The calorimetric measurement eliminates systematic uncertainties arising from the use of
external beta sources, as in experiments with beta spectrometers. This measurement was proposed in 1982 by
A. De Rujula and M. Lusignoli, but only recently the
detector technological progress allowed to design a sensitive experiment. HOLMES will deploy a large array
of low temperature microcalorimeters with implanted
163
Ho nuclei. The resulting mass sensitivity will be as
low as 0.4 eV. HOLMES will be an important step forward in the direct neutrino mass measurement with a
calorimetric approach as an alternative to spectrometry. It will also establish the potential of this approach
to extend the sensitivity down to 0.1 eV. We outline
here the project with its technical challenges and perspectives.
a
e-mail: [email protected]
1 Introduction
Assessing the neutrino mass scale is one of the major
challenges in today’s particle physics and astrophysics.
Although neutrino oscillation experiments have clearly
shown that there are at least three neutrinos with different masses, the absolute values of these masses remain unknown. Neutrino flavor oscillations are sensitive
to the difference between the squares of neutrino mass
eigenvalues and have been measured by solar, atmospheric, reactor, and accelerator experiments [1]. Combining such results, however, does not lead to an absolute value for the eigenmasses, and a dichotomy between two possible scenarios, dubbed ”normal” and ”inverted” hierarchies, exists. The scenario could be complicated further by the hypothetical existence of additional ”sterile” neutrino eigenvalues at different mass
scales [2].
The value of the neutrino mass has many implications, from cosmology to the Standard Model of particle physics. In cosmology the neutrino mass affects the
formation of large-scale structure in the universe. In
particular, neutrinos tend to damp structure clustering, before they have cooled sufficiently to become nonrelativistic, with an effect that is dependent on their
High Precision Experiments with Cold and Ultra-Cold
Neutrons
Hartmut Abele1 , Tobias Jenke1 , Erwin Jericha1 , Gertrud Konrad1 , Bastian Märkisch2 ,
Christian Plonka3 , Ulrich Schmidt2 , Torsten Soldner4 .
1
Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Wien, Austria
Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg,
Germany
3
Physikalisches Institut, Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany
4
Institut Laue-Langevin, 71 Avenue des Martyrs, 38000 Grenoble, France
2
E-mail: [email protected]
(Received October 14, 2014)
This work presents selected results from the first round of the DFG Priority Programme SPP 1491
”precision experiments in particle and astroparticle physics with cold and ultra-cold neutrons”.
KEYWORDS: Standard model, gravitation, charge quantization, neutron decay, parity violation,
CKM-matrix
1. Introduction
New high intensity sources for ultra-cold neutrons are coming into operation having the potential
to exceed contemporary source strengths by several orders of magnitude. This priority programme
wants to exploit these new technologies and implement novel concepts as a source of neutron decay
products. It addresses some of the unsolved questions of modern science: the nature of the fundamental forces and underlying symmetries, as well as the nature of the gravitational force at very
small distances. New facilities and technological developments now open the window for significant
improvement in precision by 1-2 orders of magnitude. This allows to probe these questions in a complementary way to LHC-based experiments or even constitutes a unique way. The research program
focuses on four priority areas, which are directly related to specific physics/astrophysics issues:
• Priority Area A CP-symmetry violation and particle physics in the early universe (addressed
mainly by the search for the neutron electric dipole moment)
• Priority Area B The structure and nature of weak interaction and possible extensions of the
Standard Model (addressed mainly by precise studies of the neutron β-decay)
• Priority Area C Relation between gravitation and quantum theory (probed by investigations of
low-energy bound states in the gravitational field)
• Priority Area D Charge quantization and the electric neutrality of the neutron (probed by a
precision test of the neutron’s electric charge)
The intended improvement in experimental precision has to go in parallel with the development of
new or improved measurement techniques which are often at the extreme border of feasibility.
• Priority Area E New techniques: 1) particle detection, 2) magnetometry, 3) neutron optics
This article concentrates on selected results of priority areas B, C, and D. With these priority areas
we aim for a cartography of the Standard Model of particle physics of the first particle generation
including gravitation.
Characterization of 3 mm Glass Electrodes and Development of
RPC Detectors for IN O − ICAL Experiment
Daljeet Kaur, Ashok Kumar, Ankit Gaur, Purnendu Kumar,
Md. Hasbuddin, Swati Mishra, Praveen Kumar, Md. Naimuddin∗
Department of Physics and Astrophysics, University of Delhi,
Delhi 110007, India.
December 17, 2014
Abstract
India-based Neutrino Observatory (INO) is a multi-institutional facility, planned to be built up in
South India. The INO facility will host a 51 kton magnetized Iron CALorimeter (ICAL) detector to
study atmospheric muon neutrinos. Iron plates have been chosen as the target material whereas Resistive
Plate Chambers (RPCs) have been chosen as the active detector element for the ICAL experiment. Due
to the large number of RPCs needed (∼ 28,000 of 2 m × 2 m in size) for ICAL experiment and for the long
lifetime of the experiment, it is necessary to perform a detailed R&D such that each and every parameter
of the detector performance can be optimized to improve the physics output. In this paper, we report
on the detailed material and electrical properties studies for various types of glass electrodes available
locally. We also report on the performance studies carried out on the RPCs made with these electrodes
as well as the effect of gas composition and environmental temperature on the detector performance. We
also lay emphasis on the usage of materials for RPC electrodes and the suitable enviormental conditions
applicable for operating the RPC detector for optimal physics output at INO-ICAL experiment.
Keywords: INO, ICAL, RPC, GLASS
∗ Corresponding
author: [email protected]
1
Preprint typeset in JINST style - HYPER VERSION
Automatic track recognition for large-angle
minimum ionizing particles in nuclear emulsions
T. Fukudaa∗, S. Fukunagaa , H. Ishidaa , T. Matsumotoa , T. Matsuoa , S. Mikadob ,
S. Nishimuraa , S. Ogawaa , H. Shibuyaa , J. Sudoua , A. Arigac and S. Tufanlic
a Fundamental
Physics Laboratory, Toho University,
Miyama, Funabashi J-274-8510, Japan
b Nihon University,
Narashino J-275-8576, Japan
c Laboratory for High Energy Physics (LHEP), University of Bern,
Bern CH-3012, Switzerland
A BSTRACT: We previously developed an automatic track scanning system which enables the detection of large-angle nuclear fragments in the nuclear emulsion films of the OPERA experiment.
As a next step, we have investigated this system’s track recognition capability for large-angle minimum ionizing particles (1.0 ≤ |tanθ | ≤ 3.5). This paper shows that, for such tracks, the system has
a detection efficiency of 95% or higher and reports the achieved angular accuracy of the automatically recognized tracks. This technology is of general purpose and will likely contribute not only
to various analyses in the OPERA experiment, but also to future experiments, e.g. on low-energy
neutrino and hadron interactions, or to future research on cosmic rays using nuclear emulsions
carried by balloons.
K EYWORDS : Particle tracking detectors (Solid-state detectors); Data acquisition concepts;
Performance of High Energy Physics Detectors.
∗ Corresponding
author.
Cosmic Ray Test of Mini-drift Thick Gas Electron
Multiplier Chamber for Transition Radiation Detector
S. Yanga,b,g,∗, S. Dasc , B. Bucke , C. Lia,g , T. Ljubicicb , R. Majkaf ,
M. Shaoa,g , N. Smirnovf , G. Visserd , Z. Xub , Y. Zhoua,g
a
University of Science and Technology of China, Hefei 230026, China
b
Brookhaven National Laboratory, Upton, New York 11973, USA
c
Institute of Physics, Bhubaneswar 751005, India
d
Indiana University, Bloomington, Indiana 47408, USA
e
Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
f
Yale University, New Haven, Connecticut 06520, USA
g
State Key Laboratory of Particle Detection and Electronics (USTC & IHEP), USTC,
Hefei 230026, China
Abstract
A thick gas electron multiplier (THGEM) chamber with an effective readout area of 10×10 cm2 and a 11.3 mm ionization gap has been tested along
with two regular gas electron multiplier (GEM) chambers in a cosmic ray
test system. The thick ionization gap makes the THGEM chamber a minidrift chamber. This kind mini-drift THGEM chamber is proposed as part
of a transition radiation detector (TRD) for identifying electrons at an Electron Ion Collider (EIC) experiment. Through this cosmic ray test, an efficiency larger than 94% and a spatial resolution ∼220 µm are achieved for
the THGEM chamber at -3.65 kV. Thanks to its outstanding spatial resolution and thick ionization gap, the THGEM chamber shows excellent track
reconstruction capability. The gain uniformity and stability of the THGEM
chamber are also presented.
Keywords: EIC, eSTAR, TRD, mini-drift THGEM, cosmic ray test
PACS: 25.75.Cj, 29.40.Cs
∗
Corresponding author, email address: [email protected]
Preprint submitted to Nucl. Instru. Meth. A
December 17, 2014
Prepared for submission to JHEP
arXiv:1412.5157v1 [hep-ph] 16 Dec 2014
LPN14-127
IPPP/14/107
DCPT/14/214
MCNET-14-26
ZU-TH 42/14
MITP/14-102
NLO electroweak automation and precise
predictions for W + multijet production at the LHC
S. Kallweit,a,c J. M. Lindert,a P. Maierhöfer,a,b S. Pozzorini,a and M. Schönherra,b
a
Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
Institute for Particle Physics Phenomenology, Durham University, Durham DH1 3LE, UK
c
Institut für Physik & PRISMA Cluster of Excellence, Johannes Gutenberg Universität, 55099 Mainz,
Germany
b
E-mail: [email protected], [email protected],
[email protected], [email protected],
[email protected]
Abstract: We present a fully automated implementation of next-to-leading order electroweak
(NLO EW) corrections in the OpenLoops matrix-element generator combined with the Sherpa
and Munich Monte Carlo frameworks. The process-independent character of the implemented
algorithms opens the door to NLO QCD+EW simulations for a vast range of Standard Model
processes, up to high particle multiplicity, at current and future colliders. As a first application,
we present NLO QCD+EW predictions for on-shell W -boson production in association with up
to three jets at the Large Hadron Collider. At the TeV energy scale, due to the presence of large
Sudakov logarithms, EW corrections reach the 20–40% level and play an important role for searches
of physics beyond the Standard Model. The dependence of NLO EW effects on the jet multiplicity
is investigated in detail, and we find that W + multijet final states feature genuinely different EW
effects as compared to the case of W + 1 jet.
Keywords: Electroweak radiative corrections, NLO computations, Hadronic colliders
arXiv:1412.5106v1 [astro-ph.HE] 16 Dec 2014
IceCube-Gen2 : A Vision for the Future of Neutrino Astronomy in Antarctica
M. G. Aartsen,2 M. Ackermann,54 J. Adams,16 J. A. Aguilar,12 M. Ahlers,31 M. Ahrens,44 D. Altmann,24
T. Anderson,51 G. Anton,24 C. Arguelles,31 T. C. Arlen,51 J. Auffenberg,1 S. Axani,23 X. Bai,42 I. Bartos,36
S. W. Barwick,27 V. Baum,32 R. Bay,7 J. J. Beatty,18, 19 J. Becker Tjus,10 K.-H. Becker,53 S. BenZvi,31
P. Berghaus,54 D. Berley,17 E. Bernardini,54 A. Bernhard,35 D. Z. Besson,28 G. Binder,8, 7 D. Bindig,53 M. Bissok,1
E. Blaufuss,17, ∗ J. Blumenthal,1 D. J. Boersma,52 C. Bohm,44 F. Bos,10 D. Bose,46 S. Böser,32 O. Botner,52
L. Brayeur,13 H.-P. Bretz,54 A. M. Brown,16 N. Buzinsky,23 J. Casey,5 M. Casier,13 E. Cheung,17
D. Chirkin,31 A. Christov,25 B. Christy,17 K. Clark,48 L. Classen,24 F. Clevermann,21 S. Coenders,35
G. H. Collin,14 J. M. Conrad,14 D. F. Cowen,51, 50 A. H. Cruz Silva,54 J. Daughhetee,5 J. C. Davis,18 M. Day,31
J. P. A. M. de André,22 C. De Clercq,13 S. De Ridder,26 P. Desiati,31 K. D. de Vries,13 M. de With,9 T. DeYoung,22
J. C. D´ıaz-Vélez,31 M. Dunkman,51 R. Eagan,51 B. Eberhardt,32 T. Ehrhardt,32 B. Eichmann,10 J. Eisch,31
S. Euler,52 J. J. Evans,33 P. A. Evenson,37 O. Fadiran,31 A. R. Fazely,6 A. Fedynitch,10 J. Feintzeig,31 J. Felde,17
K. Filimonov,7 C. Finley,44 T. Fischer-Wasels,53 S. Flis,44 K. Frantzen,21 T. Fuchs,21 T. K. Gaisser,37 R. Gaior,15
J. Gallagher,30 L. Gerhardt,8, 7 D. Gier,1 L. Gladstone,31 T. Gl¨
usenkamp,54 A. Goldschmidt,8 G. Golup,13
J. G. Gonzalez,37 J. A. Goodman,17 D. G´
ora,54 D. Grant,23 P. Gretskov,1 J. C. Groh,51 A. Groß,35 C. Ha,8, 7
C. Haack,1 A. Haj Ismail,26 P. Hallen,1 A. Hallgren,52 F. Halzen,31, ∗ K. Hanson,31, † J. Haugen,31 D. Hebecker,9
D. Heereman,12 D. Heinen,1 K. Helbing,53 R. Hellauer,17 D. Hellwig,1 S. Hickford,53 J. Hignight,22 G. C. Hill,2
K. D. Hoffman,17 R. Hoffmann,53 A. Homeier,11 K. Hoshina,47, 31 F. Huang,51 W. Huelsnitz,17 P. O. Hulth,44
K. Hultqvist,44 A. Ishihara,15 E. Jacobi,54 J. Jacobsen,31 G. S. Japaridze,4 K. Jero,31 O. Jlelati,26 B. J. P. Jones,14
M. Jurkovic,35 O. Kalekin,24 A. Kappes,24 T. Karg,54 A. Karle,31 T. Katori,29 U. F. Katz,24 M. Kauer,31, 38
A. Keivani,51 J. L. Kelley,31 A. Kheirandish,31 J. Kiryluk,45 J. Kläs,53 S. R. Klein,8, 7 J.-H. Köhne,21 G. Kohnen,34
H. Kolanoski,9 A. Koob,1 L. Köpke,32 C. Kopper,23, ∗ S. Kopper,53 D. J. Koskinen,20 M. Kowalski,9, 54
C. B. Krauss,23 A. Kriesten,1 K. Krings,35 G. Kroll,32 M. Kroll,10 J. Kunnen,13 N. Kurahashi,41 T. Kuwabara,15
M. Labare,26 J. L. Lanfranchi,51 D. T. Larsen,31 M. J. Larson,20 M. Lesiak-Bzdak,45 M. Leuermann,1 J. LoSecco,39
J. L¨
unemann,13 J. Madsen,43 G. Maggi,13 K. B. M. Mahn,22 S. Marka,36 Z. Marka,36 R. Maruyama,38 K. Mase,15
H. S. Matis,8 R. Maunu,17 F. McNally,31 K. Meagher,17 M. Medici,20 A. Meli,26 T. Meures,12 S. Miarecki,8, 7
E. Middell,54 E. Middlemas,31 N. Milke,21 J. Miller,13 L. Mohrmann,54 T. Montaruli,25 R. W. Moore,23
R. Morse,31 R. Nahnhauer,54 U. Naumann,53 H. Niederhausen,45 S. C. Nowicki,23 D. R. Nygren,8 A. Obertacke,53
¨ Penek,1
S. Odrowski,23 A. Olivas,17 A. Omairat,53 A. O’Murchadha,12 T. Palczewski,49 L. Paul,1 O.
J. A. Pepper,49 C. Pérez de los Heros,52 C. Pfendner,18 D. Pieloth,21 E. Pinat,12 J. L. Pinfold,23 J. Posselt,53
P. B. Price,7 G. T. Przybylski,8 J. P¨
utz,1 M. Quinnan,51 L. Rädel,1 M. Rameez,25 K. Rawlins,3 P. Redl,17
I. Rees,31 R. Reimann,1 M. Relich,15 E. Resconi,35 W. Rhode,21 M. Richman,17 B. Riedel,23 S. Robertson,2
J. P. Rodrigues,31 M. Rongen,1 C. Rott,46 T. Ruhe,21 B. Ruzybayev,37 D. Ryckbosch,26 S. M. Saba,10
H.-G. Sander,32 J. Sandroos,20 P. Sandstrom,31 M. Santander,31 S. Sarkar,20, 40 K. Schatto,32 F. Scheriau,21
T. Schmidt,17 M. Schmitz,21 S. Schoenen,1 S. Schöneberg,10 A. Schönwald,54 A. Schukraft,1 L. Schulte,11
O. Schulz,35 D. Seckel,37 Y. Sestayo,35 S. Seunarine,43 M. H. Shaevitz,36 R. Shanidze,54 M. W. E. Smith,51
D. Soldin,53 S. Söldner-Rembold,33 G. M. Spiczak,43 C. Spiering,54 M. Stamatikos,18, ‡ T. Stanev,37
N. A. Stanisha,51 A. Stasik,54 T. Stezelberger,8 R. G. Stokstad,8 A. Stößl,54 E. A. Strahler,13 R. Ström,52
N. L. Strotjohann,54 G. W. Sullivan,17 H. Taavola,52 I. Taboada,5 A. Taketa,47 A. Tamburro,37 A. Tepe,53
S. Ter-Antonyan,6 A. Terliuk,54 G. Teˇsić,51 S. Tilav,37 P. A. Toale,49 M. N. Tobin,31 D. Tosi,31 M. Tselengidou,24
E. Unger,52 M. Usner,54 S. Vallecorsa,25 N. van Eijndhoven,13 J. Vandenbroucke,31 J. van Santen,31
S. Vanheule,26 M. Vehring,1 M. Voge,11 M. Vraeghe,26 C. Walck,44 M. Wallraff,1 Ch. Weaver,31 M. Wellons,31
C. Wendt,31 S. Westerhoff,31 B. J. Whelan,2 N. Whitehorn,31 C. Wichary,1 K. Wiebe,32 C. H. Wiebusch,1
D. R. Williams,49 H. Wissing,17 M. Wolf,44 T. R. Wood,23 K. Woschnagg,7 S. Wren,33 D. L. Xu,49
X. W. Xu,6 Y. Xu,45 J. P. Yanez,54 G. Yodh,27 S. Yoshida,15 P. Zarzhitsky,49 J. Ziemann,21 and M. Zoll44
(IceCube-Gen2 Collaboration)
1
2
III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen, Germany
School of Chemistry & Physics, University of Adelaide, Adelaide SA, 5005 Australia
3
Dept. of Physics and Astronomy, University of Alaska Anchorage,
3211 Providence Dr., Anchorage, AK 99508, USA
4
CTSPS, Clark-Atlanta University, Atlanta, GA 30314, USA
5
School of Physics and Center for Relativistic Astrophysics,
Georgia Institute of Technology, Atlanta, GA 30332, USA
3
this size would have a rich physics program with the goal to resolve the sources of these astrophysical neutrinos, discover GZK neutrinos, and be a leading observatory in future multi-messenger
astronomy programs.
EXECUTIVE SUMMARY
Developments in neutrino astronomy have been driven
by the search for the sources of cosmic rays, leading,
at an early stage, to the concept of a cubic kilometer
neutrino detector. Four decades later, IceCube has discovered a flux of high-energy neutrinos of cosmic origin [1, 2]. The observed neutrino flux implies that a
significant fraction of the energy in the non-thermal universe, powered by the gravitational energy of compact
objects from neutron stars to supermassive black holes,
is generated in hadronic accelerators. High-energy neutrinos therefore hold the discovery potential to either reveal new sources or provide new insight into the energy
generation of known sources.
The observed spectrum of neutrinos, resulting from
general agreement among a sequence of independent
analyses of multiple years of IceCube data, has revealed
approximately 100 astrophysical neutrino events. The
ability of IceCube to be an efficient tool for neutrino astronomy over the next decade is limited by the modest
numbers of cosmic neutrinos measured, even in a cubic kilometer array. In this paper we present a vision
for the next-generation IceCube neutrino observatory, at
the heart of which is an expanded array of light-sensing
modules that instrument a 10 km3 volume for detection
of high-energy neutrinos. With its unprecedented sensitivity and improved angular resolution, this instrument
will explore extreme energies (PeV-scale) and will collect high-statistics samples of astrophysical neutrinos of
all flavors, enabling detailed spectral studies, significant
point source detections and new discoveries. The large
gain in event rate is made possible by the unique optical
properties of the Antarctic glacier revealed by the construction and operation of IceCube. Extremely long photon absorption lengths in the deep ice means the spacing
between strings of light sensors may exceed 250 m, enabling the instrumented volume to grow rapidly while
the cost for the high-energy array remains comparable to
that of the current IceCube detector. By roughly doubling the instrumentation already deployed, a telescope
with an instrumented volume of 10 km3 is achievable and
will yield a significant increase in astrophysical neutrino
detection rates. The instrument will provide an unprecedented view of the high-energy universe, taking neutrino
astronomy to new levels of discovery with the potential to
∗
†
‡
Authors (E. Blaufuss, F. Halzen, C. Kopper) to whom
correspondence should be addressed; [email protected].
edu, [email protected], ckopper@icecube.
wisc.edu
on leave of absence from Universit´
e Libre de Bruxelles
NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
resolve the question of the origin of the cosmic neutrinos
recently discovered [1, 2].
By delivering a significantly larger sample of highenergy neutrinos with improved angular resolution and
measurement of the energy, a detailed understanding of
the source distribution, spectrum and flavor composition
of the astrophysical neutrinos is within reach. This sample will reveal an unobstructed view of the universe at
>PeV energy, previously unexplored wavelengths where
most of the universe is opaque to high-energy photons.
The operation of a next-generation IceCube detector
in coincidence with the next generations of optical-togamma-ray telescopes and gravitational wave detectors
will present novel opportunities for multi-messenger astronomy and multi-wavelength follow-up campaigns to
obtain a complete picture of astrophysical sources.
Because of its sheer size, the high-energy array has
the potential to deliver significant samples of EeV-energy
GZK neutrinos, of anti-electron neutrinos produced via
the Glashow resonance [3], and of PeV tau neutrinos,
where both particle showers associated with the production and decay of the tau are observed. GZK neutrinos produced in interactions of extragalactic cosmic rays
with microwave photons are within reach of the instrument provided a fraction (at least at the 10% level) of the
extragalactic cosmic rays are protons. Their observation
will complement PeV neutrino astronomy and may yield
a measurement of the neutrino cross-section at center-ofmass energies of 100 TeV, testing electroweak physics at
energies beyond the reach of terrestrial accelerators.
Neutrino astronomy will be one one of many topics in
the rich science program of a next-generation neutrino
observatory. In addition to studying the properties of
cosmic rays and searching for signatures of beyond-thestandard-model neutrino physics, this world-class, multipurpose detector remains a discovery instrument for new
physics and astrophysics. For instance, the observation of
neutrinos from a supernova in our galactic neighborhood,
in coincidence with astronomical and gravitational wave
instruments, would be the astronomical event of the century, providing an unprecedented wealth of information
about this key astrophysical process.
The proposed IceCube-Gen2 high-energy array is envisioned to be the major element of a planned large-scale
enhancement to the IceCube facility at the South Pole
station. Members of the IceCube-Gen2 Collaboration,
which is now being formed, are working to develop proposals in the US and elsewhere that will include, besides this next generation IceCube high-energy detector,
the PINGU sub-array [4] that targets precision measurements of the atmospheric oscillation parameters and the
determination of the neutrino mass hierarchy. The facility’s reach may further be enhanced by exploiting the
air-shower measurement and vetoing capabilities of an
¯s0 Decays
fJ (2220) and Hadronic B
Y.K. Hsiao1,2 and C.Q. Geng1,2,3
1
Physics Division, National Center for Theoretical Sciences, Hsinchu, Taiwan 300
2
arXiv:1412.4900v1 [hep-ph] 16 Dec 2014
3
Department of Physics, National Tsing Hua University, Hsinchu, Taiwan 300
Chongqing University of Posts & Telecommunications, Chongqing, 400065, China
Abstract
¯s0 decays based on the existence of the resonant state fJ (2220). In
We study the hadronic B
¯s0 → J/ψp¯
particular, we are able to explain the unexpected large experimental result of B(B
p) =
−6 measured recently by the LHCb collaboration due to the resonant
(3.0+1.2
−1.1 ± 0.52 ± 0.03) × 10
¯s0 → J/ψfJ (2220) with fJ (2220) → p¯
contribution in B
p, while it is estimated to be at most of
¯0 →
order 10−9 in terms of the OZI rule without the resonance. In addition, we find that B(B
s
¯s0 → J/ψ(fJ →)ππ) = (15.6 ± 15.2) × 10−6 and
D ∗0 (fJ →)p¯
p) = (4.05 ± 2.46) × 10−7 , B(B
¯ < 1.6 × 10−5 and
¯ 0 → J/ψ(fJ →)K K)
¯ 0 → D ∗0 (fJ →)ππ) = (21.2 ± 20.9) × 10−7 , while B(B
B(B
s
s
¯s0 → D ∗0 (fJ →)K K)
¯ < 2.2 × 10−6 . Moreover, we predict that the decay branching ratios of
B(B
¯s0 → (J/ψ , D ∗0 )ΛΛ
¯ are (2.68 ± 1.23) × 10−7 and (2.25 ± 0.80) × 10−6 . Some of the predicted B
¯s0
B
decays are accessible to the experiments at the LHCb.
1
A light pseudoscalar of 2HDM confronted with muon g-2 and
arXiv:1412.4874v1 [hep-ph] 16 Dec 2014
experimental constraints
Lei Wang, Xiao-Fang Han
Department of Physics, Yantai University, Yantai 264005, PR China
Abstract
A light pseudoscalar of the lepton-specific 2HDM can enhance the muon g-2, but suffer from
various constraints easily, such as the 125.5 GeV Higgs signals, non-observation of additional Higgs
at the collider and even Bs → µ+ µ− . In this paper, we take the light CP-even Higgs as the
125.5 GeV Higgs, and examine the implications of those observables on a pseudoscalar with the
mass below the half of 125.5 GeV. Also the other relevant theoretical and experimental constraints
are considered. We find that the pseudoscalar can be allowed to be as low as 10 GeV, but the
corresponding tan β, sin(β−α) and the mass of charged Higgs are strongly constrained. In addition,
the surviving samples favor the wrong-sign Yukawa coupling region, namely that the 125.5 GeV
Higgs couplings to leptons have opposite sign to the couplings to gauge bosons and quarks.
PACS numbers: 12.60.Fr, 14.80.Ec, 14.80.Bn
1
DESY 14-240
Rapidity-Dependent Jet Vetoes
Shireen Gangal, Maximilian Stahlhofen, and Frank J. Tackmann
arXiv:1412.4792v1 [hep-ph] 15 Dec 2014
Theory Group, Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg, Germany
Jet vetoes are a prominent part of the signal selection in various analyses at the LHC. We discuss
jet vetoes for which the transverse momentum of a jet is weighted by a smooth function of the jet
rapidity. With a suitable choice of the rapidity-weighting function, such jet-veto variables can be
factorized and resummed allowing for precise theory predictions. They thus provide a complementary way to divide phase space into exclusive jet bins. In particular, they provide a natural and
theoretically clean way to implement a tight veto on central jets with the veto constraint getting
looser for jets at increasingly forward rapidities. We mainly focus our discussion on the 0-jet case
in color-singlet processes, using Higgs production through gluon fusion as a concrete example. For
one of our jet-veto variables we compare the resummed theory prediction at NLL0 +NLO with the
recent differential cross section measurement by the ATLAS experiment in the H → γγ channel,
finding good agreement. We also propose that these jet-veto variables can be measured and tested
against theory predictions in other SM processes, such as Drell-Yan, diphoton, and weak diboson
production.
I.
INTRODUCTION
Jet vetoes play an important role at the LHC in Higgs
property measurements as well as in searches for physics
beyond the Standard Model. They are utilized to reduce
backgrounds and more generally are used to classify the
data into exclusive categories, “jet bins”, based on the
number of hadronic jets in the final state. The default jet
variable by which jets are currently classified and vetoed
is the transverse momentum pT j of a jet.
While a veto on additional jets can be desirable in
many contexts, the application of a tight jet veto is usually subject to both theoretical and experimental limitations. Theoretically, applying a tight jet veto leads to
Sudakov double logarithms of the jet-veto variable in perturbation theory, which as the veto gets tighter (smaller
veto cuts) become larger and dominate the perturbative
series, leading to increased theoretical uncertainties in
the fixed-order (FO) predictions [1]. This can be remedied by systematically resumming the jet-veto logarithms
to all orders [2–17], provided that the considered jet-veto
variable is resummable and under good enough theoretical control.
Experimentally, jets can only be robustly reconstructed down to some minimum pT , which limits how
low one can go in the jet veto cut, i.e., how tight one can
make the jet veto. Furthermore, in harsh pile-up conditions low-pT jets are particularly hard to identify at
forward rapidities (beyond |η| >
∼ 2.5), when a large part
or all of the jet area lies in a detector region where no
tracking information is available.
In principle, one possibility would be to place a hard
cut on the (pseudo)rapidity ηj of the classified jets, i.e.,
one only considers and possibly vetoes jets within a certain range of central rapidities, |ηj | < η cut . Theoretically,
such a hard rapidity cut represents a nonglobal measurement and changes the logarithmic structure [7]. This
means that a priori it is not clear how to consistently
incorporate it into the jet-veto resummation at higher
orders, and none of the present jet-veto resummations
for pT j actually includes such a rapidity cut. (In Monte
Carlo studies, a cut at η cut ∼ 2.5 has an O(10%) effect
on the cross section for typical pT j vetoes [4, 5].) Another option, which avoids a hard rapidity cut, is to raise
the cut on pT j , and thus loosen the jet veto everywhere.
Clearly, this may also not be ideal since one now looses
the utility of a tight jet veto for central jets.
In this paper, we discuss a class of jet-veto variables
which explicitly depend on the jet rapidity yj ,
Tf j = pT j f (yj ) ,
(1)
where f (yj ) is some weighting function of yj . (The difference between ηj and yj due to a nonzero jet mass is
not relevant for now and either could be used. We will
come back to this at the end of Sec. II.)
By classifying jets according to Tf j and only allowing jets with Tf j < T cut , we effectively have a rapiditydependent veto on pT j ,
pT j <
T cut
.
f (yj )
(2)
If the weighting function f (y) is chosen as a decreasing function of |y| this corresponds to a veto which gets
tighter at central rapidities and looser at forward rapidities. Effectively, the contribution of forward jets is then
smoothly suppressed by the weighting function f (yj ). At
the same time, f (yj ) can be chosen such that explicit theoretical control is maintained. In fact, all the variables
we discuss can be resummed to a similar (and possibly
higher) level of precision as pT j . In this way, one can
largely avoid the theoretical and experimental limitations
discussed above. (Of course, the lowest Tf j values that
can be measured are ultimately still limited by how well
central jets can be measured.)
Apart from such practical considerations, given the
usefulness of jet binning, it is clearly beneficial to have
several alternative and complementary ways to perform
FERMILAB-PUB-14-517-T
IPMU14-0346
arXiv:1412.4789v1 [hep-ph] 15 Dec 2014
The Relic Neutralino Surface at a 100 TeV collider
Joseph Bramante,a Patrick J. Fox,b Adam Martin,a Bryan Ostdiek,a Tilman Plehn,c Torben
Schell,c and Michihisa Takeuchid
a
Department of Physics, University of Notre Dame, IN, USA
Theoretical Physics Department, Fermilab, Batavia, IL USA
c
Institut f¨
ur Theoretische Physik, Universit¨
at Heidelberg, Germany
d
Kavli IPMU (WPI), The University of Tokyo, Kashiwa, Japan
b
Abstract: We map the parameter space for MSSM neutralino dark matter which freezes out
to the observed relic abundance, in the limit that all superpartners except the neutralinos and
charginos are decoupled. In this space of relic neutralinos, we show the dominant dark matter
annihilation modes, the mass splittings among the electroweakinos, direct detection rates, and
collider cross-sections. The mass difference between the dark matter and the next-to-lightest
neutral and charged states is typically much less than electroweak gauge boson masses. With
these small mass differences, the relic neutralino surface is accessible to a future 100 TeV hadron
collider, which can discover inter-neutralino mass splittings down to 1 GeV and thermal relic dark
matter neutralino masses up to 1.5 TeV with a few inverse attobarns of luminosity. This coverage
is a direct consequence of the increased collider energy: in the Standard Model events with missing
transverse momentum in the TeV range have mostly hard electroweak radiation, distinct from the
soft radiation shed in compressed electroweakino decays. We exploit this kinematic feature in final
states including photons and leptons, tailored to the 100 TeV collider environment.
YITP-SB-14-53
Uncovering light scalars with exotic Higgs decays to b¯bµ+ µ−
David Curtin,1, ∗ Rouven Essig,2, † and Yi-Ming Zhong2, ‡
1
arXiv:1412.4779v1 [hep-ph] 15 Dec 2014
2
Maryland Center for Fundamental Physics, University of Maryland, College Park, MD 20742
C. N. Yang Institute for Theoretical Physics, Stony Brook University, Stony Brook, NY 11794
The search for exotic Higgs decays are an essential probe of new physics. In particular, the small
width of the Higgs boson makes its decay uniquely sensitive to the existence of light hidden sectors.
Here we assess the potential of an exotic Higgs decay search for h → 2X → b¯bµ+ µ− to constrain
theories with light CP-even (X = s) and CP-odd (X = a) singlet scalars in the mass range of
15 to 60 GeV. This decay channel arises naturally in many scenarios, such as the Standard Model
augmented with a singlet, the two-Higgs-doublet model with a singlet (2HDM+S) – which includes
the Next-to-Minimal Supersymmetric Standard Model (NMSSM) – and in hidden valley models.
The 2b2µ channel may represent the best discovery avenue for many models. It has competitive
reach, and is less reliant on low-pT b- and τ -reconstruction compared to other channels like 4b,
4τ , and 2τ 2µ. We analyze the sensitivity of a 2b2µ search for the 8 and 14 TeV LHC, including
the HL-LHC. We consider three types of analyses, employing conventional resolved b-jets with a
clustering radius of R ∼ 0.4, thin b-jets with R = 0.2, and jet substructure techniques, respectively.
The latter two analyses improve the reach for mX ∼ 15 GeV, for which the two b-jets are boosted
and often merged. We find that Br(h → 2X → 2b2µ) can be constrained at the few × 10−5 level
across the entire considered mass range of X at the HL-LHC. This corresponds to a 1 − 10% reach in
Br(h → 2X) in 2HDM+S models, including the NMSSM, depending on the type of Higgs Yukawa
couplings.
I.
INTRODUCTION
The discovery of the 125 GeV Higgs boson at the Large
Hadron Collider (LHC) [1, 2] opens up several new experimental frontiers. The complete characterization of this
new particle, including the precise measurements of its
couplings, searches for Higgs “siblings”, and searches for
non-standard (exotic) decay modes [3–5], has the great
potential to reveal signs of physics beyond the Standard
Model (SM). Among the most exciting possibilities is
that the Higgs boson can provide a unique window onto
light hidden sectors, consisting of particles neutral under
the SM gauge groups.
The Higgs boson is one of only a few SM particles
that can couple to new states with an interaction that
is (super-)renormalizable. In addition, the small decay
width of the SM Higgs, dominated by the bottom Yukawa
coupling, means that a small, O(0.01), renormalizable
coupling of the Higgs to a new, light state can lead to
an exotic Higgs decay branching fraction of O(1). This
makes exotic Higgs decays a prime experimental target.
In many cases, these exotic decays need to be searched
for explicitly as they may otherwise escape detection. In
particular, measurements of the Higgs couplings to SM
states only constrains the Higgs branching ratio to nonSM states to . 60% [6, 7]. Thus a large branching ratio to
beyond SM particles is still viable. For a detailed survey
of promising exotic decay modes and their theoretical
motivations we refer the reader to [3].
One interesting category of exotic Higgs decays contains final states with four SM fermions and no missing
energy: h → XX 0 → 2f 2f 0 , where X and X 0 are onshell, and we here assume that they are the same particle, X = X 0 .1 Generically, the couplings of X determine the optimal search strategy. If X is a dark photon,
i.e. the mediator of a new, broken U (1) gauge theory
which kinetically mixes with the SM hypercharge gauge
boson [8–10], then the couplings of X to SM particles
are gauge-ordered, i.e. the X couplings are related to
the SM Z-boson and photon couplings to SM fermions.
In this case, the X has an O(1) branching fraction to
light leptons, making h → 4` the best discovery channel [3, 11–19]. On the other hand, if X is a CP-odd2
scalar (a) or a CP-even scalar (s), it generically inherits its couplings from the SM Higgs sector. This means
that the couplings of X to the SM fermions are typically
Yukawa-ordered, so that its largest branching fraction
is to the heaviest fermion that is kinematically accessible. For this reason, previous LHC studies have extensively focused on the decay channels h → 4b [20–25]
and h → 2b2τ [24, 26] for mX > 2mb , h → 4τ [27, 28]
and h → 2τ 2µ [29, 30] for 2mτ < mX < 2mb , and
h → 4µ [30–33] for 2mµ < mX < 2mτ . These searches
are motivated in the context of, for example, the SM
with a singlet (see e.g. [3]); the two-Higgs-doublet model
with an additional singlet (2HDM+S, see e.g. [3, 5]),
including the next-to-minimal supersymmetric standard
model (NMSSM) [34–36]; the minimal supersymmetric
1
∗ [email protected]
† [email protected]
‡ [email protected]
2
We use the shorthand, for example, ‘2f ’ or ‘4f ’ to denote f f¯ of
f f¯f f¯, respectively.
In this study, we will only consider CP-conserving Higgs sectors.
Minimum Bias, MPI and DPS, Diffractive and Exclusive measurements at
CMS
Dipanwita Dutta on behalf of CMS Collaboration
Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai-400085, India.
arXiv:1412.4977v1 [hep-ex] 16 Dec 2014
Abstract
We present recent results on Minimum Bias, MPI and DPS, Diffractive and Exclusive studies√using data
collected during Run 1 of the LHC. The measurements include data collected in pp collisions at s = 7, and
8 TeV by the CMS Collaboration. Double parton scattering is investigated in several final states including
vector bosons and jets, and the effective cross section results are compared to other experiments and to
MPI models tuned to recent underlying event measurements at CMS. Inclusive diffractive cross sections
are discussed and compared to models, while searches and measurements of central exclusive processes are
presented. The results from the first combined measurement by the CMS+TOTEM collaborations of the
pseudorapidity distribution of charged particles at 8 TeV are also discussed, and are compared to models
and to lower energy measurements.
Keywords: LHC, rapidity gaps, soft QCD, underlying events
1. Introduction
Forward, diffractive and exclusive physics cover
a wide range of subjects, including low-x QCD, underlying event and multiple interactions characteristics, and central exclusive process. With excellent
performance the Compact Muon Solenoid (CMS)
experiment [1] has made a number of significant
observations in diffractive and exclusive processes
and hence to probe the Standard model in a unique
way. The particle production in pp collisions at
LHC, will allow to test the fundamental aspect of
QCD, namely the interplay between soft and hard
contributions to an interaction. Its good understanding is crucial for the proper modeling of the
final state of Minimum-Bias events, and can help
improve the simulation of e.g. the underlying event,
pile-up events, and the measurement of the machine
luminosity at the LHC. In this paper, we present the
recent CMS results on diffraction, forward physics
and soft QCD, and discuss their comparison to predictions of various theoretical models.
2. Diffractive processes
Diffractive interactions are characterized by the
presence of at least one non-exponentially supPreprint submitted to Elsevier
Figure 1: Schematic diagrams of (a) non-diffractive, pp →
X, and diffractive processes with (b) single dissociation,
pp → Xp or pp → pY , (c) double-dissociation, pp → XY ,
and (d) central dissociation, pp → pXp. The X(Y) represents a dissociated-proton or a centrally-produced hadronic
system.
pressed large rapidity gap (LRG) in the final state.
LRG is defined as a region in pseudorapidity devoid of particles is presumed to be formed by a
color-singlet exchange with vacuum quantum numbers, referred to as Pomeron (IP) exchange. Inclusive (soft) diffractive interactions (with no hard
scale) cannot be calculated within perturbative
QCD (pQCD), and traditionally have been described by models based on Regge theory. Model
predictions generally differ when extrapolated from
pre-LHC energies (e.g. 1.96 TeV) to 7 TeV at LHC.
Thus experimental results at LHC provide important input for tuning various models and current
December 17, 2014
arXiv:1412.4946v1 [hep-ex] 16 Dec 2014
Inclusive B → Xs γ and B → Xs `+ `− at the B factories
John Walsh
INFN, Sezione di Pisa
Largo B. Pontecorvo 3, 56127 Pisa, ITALY
I report here recent measurements of observables from the inclusive decays B →
Xs γ and B → Xs `+ `− . Included are measurements of the branching fractions and CP
asymmetries for both channels, as well as the forward-backward lepton asymmetry in
inclusive B → Xs `+ `− decays, which is the first measurement of this quantity.
PRESENTED AT
FPCP 2014 – Flavor Physics & CP Violation
Marseille, France, May 26–30, 2014
1
Introduction
Radiative and electroweak penguin decays, in particular the decays B → Xs γ and B → Xs `+ `− ,
have proven to be powerful probes of New Physics (NP) in the flavour sector. These flavour-changing
neutral current decays are prohibited at tree level in the Standard Model (SM). This makes them
sensitive to NP effects, which can contribute at the same level as the SM, namely at the one-loop
level, as can be seen in Fig. 1. A general review of radiative and electroweak penguin physics can
Figure 1: Lowest order SM diagrams for B → Xs γ and B → Xs `+ `− decays.
be found in section 17.9 of reference [1]. One usually distinguishes between exclusive and inclusive
measurements, where in the former case, the measurement is performed on a particular final state,
for example B 0 → K ∗0 γ. Recent results on exclusive measurements were presented at this conference
by Patrick Owen and Akimasa Ishikawa [2]. Inclusive analyses attempt to include all final states
for a given parton level process. This has theoretical advantages, since the calculation of inclusive
radiative and electroweak penguin decays is much more precise than the corresponding calculations
on exclusive decay modes. In the latter, hadronic effects tend to cause theoretical uncertainties to
grow significantly.
From an experimental point of view, truly inclusive measurements are significantly more challenging: since the B decay is not fully reconstructed, there are fewer kinematic constraints available
in the event selection. Typically, a fully-inclusive measurement will try to tag one B meson in the
event and then look for an inclusive signature of the signal from the other B. An example would be
requiring a high-pT lepton to tag a semi-leptonic B decay and then require a high-energy photon in
the same event, as a signal of the B → Xs γ process. In such fully inclusive analyses the backgrounds
generally tend to be higher than for exclusive measurements, leading to higher uncertainties.
This difficulty is somewhat alleviated with the sum-of-exclusives (SOE) technique, whereby a
large number (typically tens) of exclusive final states are reconstructed to capture as much as the
full rate as possible. Usually 50–70% of the total rate is selected and the missing part must be
estimated using simulation. This generally leads to a larger systematic uncertainty than one obtains
with the fully inclusive techniques.
In these proceedings, I will report on a measurement of the CP asymmetry in inclusive B → Xs γ
decays, using a fully inclusive method, as well as measurements of the branching fraction and CP
asymmetry using the sum-of-exclusives technique. I will also report measurements of the branching
fraction, CP asymmetry and forward-backward (FB) lepton asymmetry in B → Xs `+ `− decays.
The FB lepton asymmetry measurement is the first ever made of this quantity for the inclusive
decay.
All measurements reported were performed either at Belle [3] or Babar [4], the two B factory
experiments. Each of these detectors operated at an e+ e− collider operating at a center-of-mass
energy of 10.58 GeV, equal to the mass of the Υ(4S) resonance.
1
arXiv:1412.4827v1 [hep-ex] 15 Dec 2014
Search for production of an Υ(1S) meson in association with a W or Z boson using the
full 1.96 TeV p¯
p collision data set at CDF
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W. Badgett,15 T. Bae,25 A. Barbaro-Galtieri,26 V.E. Barnes,43 B.A. Barnett,23 P. Barriamm ,41 P. Bartos,12
M. Baucekk ,39 F. Bedeschi,41 S. Behari,15 G. Bellettinill ,41 J. Bellinger,54 D. Benjamin,14 A. Beretvas,15
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P. Bussey,19 P. Buttill ,41 A. Buzatu,19 A. Calamba,10 S. Camarda,4 M. Campanelli,28 F. Canellidd ,11 B. Carls,22
D. Carlsmith,54 R. Carosi,41 S. Carrillol ,16 B. Casalj ,9 M. Casarsa,48 A. Castrojj ,6 P. Catastini,20 D. Cauzrr ss ,48
V. Cavaliere,22 A. Cerrie ,26 L. Cerritor ,28 Y.C. Chen,1 M. Chertok,7 G. Chiarelli,41 G. Chlachidze,15 K. Cho,25
D. Chokheli,13 A. Clark,18 C. Clarke,53 M.E. Convery,15 J. Conway,7 M. Corboz ,15 M. Cordelli,17 C.A. Cox,7
D.J. Cox,7 M. Cremonesi,41 D. Cruz,47 J. Cuevasy ,9 R. Culbertson,15 N. d’Ascenzov ,15 M. Dattagg ,15
P. de Barbaro,44 L. Demortier,45 M. Deninno,6 M. D’Erricokk ,39 F. Devoto,21 A. Di Cantoll ,41 B. Di Ruzzap ,15
J.R. Dittmann,5 S. Donatill ,41 M. D’Onofrio,27 M. Dorigott ,48 A. Driuttirr ss ,48 K. Ebina,52 R. Edgar,31 A. Elagin,47
R. Erbacher,7 S. Errede,22 B. Esham,22 S. Farrington,38 J.P. Fernández Ramos,29 R. Field,16 G. Flanagant ,15
R. Forrest,7 M. Franklin,20 J.C. Freeman,15 H. Frisch,11 Y. Funakoshi,52 C. Gallonill ,41 A.F. Garfinkel,43
P. Garosimm ,41 H. Gerberich,22 E. Gerchtein,15 S. Giagu,46 V. Giakoumopoulou,3 K. Gibson,42 C.M. Ginsburg,15
N. Giokaris,3 P. Giromini,17 V. Glagolev,13 D. Glenzinski,15 M. Gold,34 D. Goldin,47 A. Golossanov,15 G. Gomez,9
G. Gomez-Ceballos,30 M. Goncharov,30 O. González López,29 I. Gorelov,34 A.T. Goshaw,14 K. Goulianos,45
E. Gramellini,6 C. Grosso-Pilcher,11 R.C. Group,51, 15 J. Guimaraes da Costa,20 S.R. Hahn,15 J.Y. Han,44
F. Happacher,17 K. Hara,49 M. Hare,50 R.F. Harr,53 T. Harrington-Taberm ,15 K. Hatakeyama,5 C. Hays,38
J. Heinrich,40 M. Herndon,54 A. Hocker,15 Z. Hong,47 W. Hopkinsf ,15 S. Hou,1 R.E. Hughes,35 U. Husemann,55
M. Husseinbb ,32 J. Huston,32 G. Introzzioopp ,41 M. Ioriqq ,46 A. Ivanovo ,7 E. James,15 D. Jang,10 B. Jayatilaka,15
E.J. Jeon,25 S. Jindariani,15 M. Jones,43 K.K. Joo,25 S.Y. Jun,10 T.R. Junk,15 M. Kambeitz,24 T. Kamon,25, 47
P.E. Karchin,53 A. Kasmi,5 Y. Katon ,37 W. Ketchumhh ,11 J. Keung,40 B. Kilminsterdd ,15 D.H. Kim,25 H.S. Kim,25
J.E. Kim,25 M.J. Kim,17 S.H. Kim,49 S.B. Kim,25 Y.J. Kim,25 Y.K. Kim,11 N. Kimura,52 M. Kirby,15 K. Knoepfel,15
K. Kondo,52, ∗ D.J. Kong,25 J. Konigsberg,16 A.V. Kotwal,14 M. Kreps,24 J. Kroll,40 M. Kruse,14 T. Kuhr,24
M. Kurata,49 A.T. Laasanen,43 S. Lammel,15 M. Lancaster,28 K. Lannonx ,35 G. Latinomm ,41 H.S. Lee,25 J.S. Lee,25
S. Leo,41 S. Leone,41 J.D. Lewis,15 A. Limosanis ,14 E. Lipeles,40 A. Listera ,18 H. Liu,51 Q. Liu,43 T. Liu,15
S. Lockwitz,55 A. Loginov,55 D. Lucchesikk ,39 A. Lucà,17 J. Lueck,24 P. Lujan,26 P. Lukens,15 G. Lungu,45
J. Lys,26 R. Lysakd ,12 R. Madrak,15 P. Maestromm ,41 S. Malik,45 G. Mancab ,27 A. Manousakis-Katsikakis,3
L. Marcheseii ,6 F. Margaroli,46 P. Marinonn ,41 K. Matera,22 M.E. Mattson,53 A. Mazzacane,15 P. Mazzanti,6
R. McNultyi ,27 A. Mehta,27 P. Mehtala,21 C. Mesropian,45 T. Miao,15 D. Mietlicki,31 A. Mitra,1 H. Miyake,49
S. Moed,15 N. Moggi,6 C.S. Moonz ,15 R. Mooreeef f ,15 M.J. Morellonn ,41 A. Mukherjee,15 Th. Muller,24
P. Murat,15 M. Mussinijj ,6 J. Nachtmanm ,15 Y. Nagai,49 J. Naganoma,52 I. Nakano,36 A. Napier,50
J. Nett,47 C. Neu,51 T. Nigmanov,42 L. Nodulman,2 S.Y. Noh,25 O. Norniella,22 L. Oakes,38 S.H. Oh,14
Y.D. Oh,25 I. Oksuzian,51 T. Okusawa,37 R. Orava,21 L. Ortolan,4 C. Pagliarone,48 E. Palenciae ,9 P. Palni,34
V. Papadimitriou,15 W. Parker,54 G. Paulettarr ss ,48 M. Paulini,10 C. Paus,30 T.J. Phillips,14 G. Piacentinoq ,15
E. Pianori,40 J. Pilot,7 K. Pitts,22 C. Plager,8 L. Pondrom,54 S. Poprockif ,15 K. Potamianos,26 A. Pranko,26
F. Prokoshinaa ,13 F. Ptohosg ,17 G. Punzill ,41 I. Redondo Fernández,29 P. Renton,38 M. Rescigno,46 F. Rimondi,6, ∗
L. Ristori,41, 15 A. Robson,19 T. Rodriguez,40 S. Rollih ,50 M. Ronzanill ,41 R. Roser,15 J.L. Rosner,11 F. Ruffinimm ,41
A. Ruiz,9 J. Russ,10 V. Rusu,15 W.K. Sakumoto,44 Y. Sakurai,52 L. Santirr ss ,48 K. Sato,49 V. Savelievv ,15
A. Savoy-Navarroz ,15 P. Schlabach,15 E.E. Schmidt,15 T. Schwarz,31 L. Scodellaro,9 F. Scuri,41 S. Seidel,34
Y. Seiya,37 A. Semenov,13 F. Sforzall ,41 S.Z. Shalhout,7 T. Shears,27 P.F. Shepard,42 M. Shimojimau ,49
M. Shochet,11 I. Shreyber-Tecker,33 A. Simonenko,13 K. Sliwa,50 J.R. Smith,7 F.D. Snider,15 H. Song,42
V. Sorin,4 R. St. Denis,19, ∗ M. Stancari,15 D. Stentzw ,15 J. Strologas,34 Y. Sudo,49 A. Sukhanov,15 I. Suslov,13
K. Takemasa,49 Y. Takeuchi,49 J. Tang,11 M. Tecchio,31 P.K. Teng,1 J. Thomf ,15 E. Thomson,40 V. Thukral,47
D. Toback,47 S. Tokar,12 K. Tollefson,32 T. Tomura,49 D. Tonellie ,15 S. Torre,17 D. Torretta,15 P. Totaro,39
M. Trovatonn ,41 F. Ukegawa,49 S. Uozumi,25 F. Vázquezl ,16 G. Velev,15 C. Vellidis,15 C. Vernierinn ,41 M. Vidal,43
R. Vilar,9 J. Vizáncc ,9 M. Vogel,34 G. Volpi,17 P. Wagner,40 R. Wallnyj ,15 S.M. Wang,1 D. Waters,28
W.C. Wester III,15 D. Whitesonc ,40 A.B. Wicklund,2 S. Wilbur,7 H.H. Williams,40 J.S. Wilson,31 P. Wilson,15
3
48
Istituto Nazionale di Fisica Nucleare Trieste, rr Gruppo Collegato di Udine,
ss
University of Udine, I-33100 Udine, Italy, tt University of Trieste, I-34127 Trieste, Italy
49
University of Tsukuba, Tsukuba, Ibaraki 305, Japan
50
Tufts University, Medford, Massachusetts 02155, USA
51
University of Virginia, Charlottesville, Virginia 22906, USA
52
Waseda University, Tokyo 169, Japan
53
Wayne State University, Detroit, Michigan 48201, USA
54
University of Wisconsin, Madison, Wisconsin 53706, USA
55
Yale University, New Haven, Connecticut 06520, USA
Production of the Υ(1S) meson in association with a vector boson is a rare process in the standard
model with a cross section predicted to be below the sensitivity of the Tevatron. Observation of this
process could signify contributions not described by the standard model or reveal limitations with
the current non-relativistic quantum-chromodynamic models used to calculate the cross section. We
perform a search for this process using the full Run II data set collected by the CDF II detector
corresponding to an integrated luminosity of 9.4 fb−1 . The search considers the Υ → µµ decay
and the decay of the W and Z bosons into muons and electrons. In these purely leptonic decay
channels, we observe one ΥW candidate with an expected background of 1.2 ± 0.5 events, and one
ΥZ candidate with an expected background of 0.1 ± 0.1 events. Both observations are consistent
with the predicted background contributions. The resulting upper limits on the cross section for
Υ + W/Z production are the most sensitive reported from a single experiment and place restrictions
on potential contributions from non-standard-model physics.
PACS numbers: 14.70.-e, 4.40.Pq, 12.39.Jh
I.
∗
†
Deceased
With visitors from a University of British Columbia, Vancouver, BC V6T 1Z1, Canada, b Istituto Nazionale di Fisica
Nucleare, Sezione di Cagliari, 09042 Monserrato (Cagliari),
Italy, c University of California Irvine, Irvine, CA 92697, USA,
d Institute of Physics, Academy of Sciences of the Czech Republic, 182 21, Czech Republic, e CERN, CH-1211 Geneva, Switzerland, f Cornell University, Ithaca, NY 14853, USA, g University
of Cyprus, Nicosia CY-1678, Cyprus, h Office of Science, U.S. Department of Energy, Washington, DC 20585, USA, i University
College Dublin, Dublin 4, Ireland, j ETH, 8092 Z¨
urich, Switzerland, k University of Fukui, Fukui City, Fukui Prefecture, Japan
910-0017, l Universidad Iberoamericana, Lomas de Santa Fe,
m
M´
exico, C.P. 01219, Distrito Federal,
University of Iowa,
Iowa City, IA 52242, USA, n Kinki University, Higashi-Osaka
City, Japan 577-8502, o Kansas State University, Manhattan,
KS 66506, USA, p Brookhaven National Laboratory, Upton, NY
11973, USA, q Istituto Nazionale di Fisica Nucleare, Sezione di
Lecce, Via Arnesano, I-73100 Lecce, Italy, r Queen Mary, University of London, London, E1 4NS, United Kingdom, s University of
Sydney, NSW 2006, Australia, t Muons, Inc., Batavia, IL 60510,
USA, u Nagasaki Institute of Applied Science, Nagasaki 8510193, Japan, v National Research Nuclear University, Moscow
115409, Russia, w Northwestern University, Evanston, IL 60208,
USA, x University of Notre Dame, Notre Dame, IN 46556,
USA, y Universidad de Oviedo, E-33007 Oviedo, Spain, z CNRSIN2P3, Paris, F-75205 France, aa Universidad Tecnica Federico
Santa Maria, 110v Valparaiso, Chile, bb The University of Jordan, Amman 11942, Jordan, cc Universite catholique de Louvain,
1348 Louvain-La-Neuve, Belgium, dd University of Z¨
urich, 8006
Z¨
urich, Switzerland, ee Massachusetts General Hospital, Boston,
MA 02114 USA, f f Harvard Medical School, Boston, MA 02114
USA, gg Hampton University, Hampton, VA 23668, USA, hh Los
Alamos National Laboratory, Los Alamos, NM 87544, USA,
ii Universit`
a degli Studi di Napoli Federico I, I-80138 Napoli,
Italy
INTRODUCTION
The standard model production of an upsilon (Υ) meson in association with a W boson or a Z boson is a
rare process whose rate was first calculated in Ref. [1],
where ΥW and ΥZ production occur through the partonlevel processes producing W + b¯b and Z + b¯b final states,
in which the b¯b pair may form a bound state (either
an Υ or an excited bottomonium state that decays to
an Υ). More recently, rates for these processes have
been calculated at next-to-leading-order in the stronginteraction coupling for proton-antiproton (p¯
p) collisions
at 1.96 TeV center-of-mass energy and proton-proton collisions at 8 TeV and 14 TeV [2] .
The cross sections calculated for ΥW and ΥZ production in p¯
p collisions at 1.96 TeV are 43 fb and 34 fb,
respectively. These values were calculated at leadingorder using the Madonia quarkonium generator [3] as
detailed below and are roughly a factor of ten smaller
than the earlier calculations from Ref. [1]. The calculations of these processes are very sensitive to the nonrelativistic quantum-chromodynamic (NRQCD) models,
especially the numerical values of the long-distance matrix elements (LDME), which determine the probability
that a b¯b will form a bottomonium state. Measurements
of Υ + W/Z cross sections are important for validating
these NRQCD models.
Supersymmetry (SUSY) is an extension of the standard model (SM) which has not been observed. Reference [1] describes some SUSY models in which charged
Higgs bosons can decay into ΥW final states with a large
branching fraction (B). Similarly, in addition to the expected decays of a SM Higgs to an ΥZ pair, further light
neutral scalars may decay into ΥZ. Therefore, if the observed rate of ΥW and/or ΥZ production is significantly
Separation of flow from chiral magnetic effect in U+U collisions using spectator
asymmetry
Sandeep Chatterjee∗ and Prithwish Tribedy†
Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata, 700064, India
arXiv:1412.5103v1 [nucl-th] 16 Dec 2014
Abstract
We demonstrate that the prolate shape of the Uranium nucleus generates anti-correlation between spectator asymmetry
and initial state ellipticity of the collision zone, providing a way to constrain the initial event shape in U+U collisions. As
an application, we show that this can be used to separate the background contribution due to flow from the signals of chiral
magnetic effect.
The hot and dense QCD plasma produced in heavy
ion collisions (HIC) can give rise to metastable vacuum
with non trivial topology of the gauge field configurations
like sphalerons and instantons. These give rise to P and
CP odd interactions between quark and gluon fields that
change the quark chirality [1, 2]. In the early stages of
HICs, strong magnetic fields∼ m2π are expected to be
produced [3–5]. This unique combination of local P and
CP odd domains amidst strong magnetic field in HIC
experiments is expected to give rise to many interesting
phenomena like the chiral magnetic effect (CME) [6]. The
separation of charged hadrons along the direction of the
magnetic field have been suggested as a possible signal of
CME in which the like sign charges are expected to be
emitted in the same direction [2]. However, such angular
correlations can also arise due to non-CME effects like
elliptic flow, resonance decays, momentum conservation
kinematics etc [7]. In order to reduce the non-flow effects,
the following charged particle correlator was proposed in
Ref. [8]
γ ab = hcos φa + φb − 2ψRP i.
(1)
There have been suggestions on disentangling the CME
from flow [14, 15]. In Au+Au collisions, it has been suggested that within a narrow centrality bin large fluctuation of the initial state ellipticity produces a broad event
by event distribution of v2 while CME is expected to
be nearly constant because of similar number of spectators [15], thereby disentangling the two effects.
The other approach is to study the collisions of deformed nucleus such as Uranium [14]. It has been pointed
out that in full overlap U+U collisions, the magnetic
field in the overlap zone nearly vanishes, although a large
anisotropy is generated from certain configurations of the
prolate shape of the Uranium nucleus. This allows one
to turn off CME while having substantial v2 in such collisions [14].
In this work we propose a new method to systematically reduce the initial anisotropy that contributes to v2
in a given sample of events without reducing the effect
of magnetic field that generates the signals of CME in
U+U collisions. For further discussions we introduce a
quantity, the spectator nucleon asymmetry |L − R| which
is defined as the absolute difference between the left (L)
and right (R) going nucleons that did not participate in
the collision. In case of the collisions of non-deformed
nuclei like Pb, the spherical shape of the individual nucleus ensures that |L − R| receives no contribution from
the collision geometry. The non-zero values of |L − R| in
such cases can arise only due to quantum fluctuations of
the nucleon positions in the colliding nuclei. Here we will
not focus on such initial state fluctuations. In the case of
U+U collisions, |L − R| receives a dominant contribution
from the geometric fluctuations. We argue and demonstrate through Monte Carlo Glauber (MCG) simulations
that |L − R| is an important tuning parameter to constrain the initial state geometry in U+U collisions that
can be useful for several purposes.
Deformed nuclear collisions are characterized by four
angles representing the orientations of the major axes of
the colliding nuclei in addition to the impact parameter
b [14, 16–18]. They include the two polar angles Θ1 and
Θ2 relative to the collision direction (z-axis) as shown in
Fig. 1 and two azimuthal angles Φ1 and Φ2 in the plane
transverse to the collision direction, the collision plane.
Here φ is the azimuthal angle of the particle and a, b = ±,
is its charge state. ψRP is the reaction plane angle. The
non-flow effects that are random with respect to ψRP are
eliminated by the design of this observable. It is however difficult to reduce the background from elliptic flow.
The elliptic flow v2 is largely characterised by the initial
shape of the collision zone and the strength of CME signal depends on the number of spectators. It turns out
that the attempts to reduce flow, say by going towards
central events, also reduces the magnetic field and therefore the signal of CME due to decrease in the number of
spectators. Therefore, although γ ab has been measured
in Au+Au, Cu+Cu and Pb+Pb collisions [9–12], the final
verdict on CME is still not out. This is mainly because
it is not possible to separate the background flow effects
from γ ab unambiguously by conventional approaches [13].
∗
†
[email protected]
[email protected]
1
arXiv:1412.5097v1 [hep-lat] 16 Dec 2014
Neutral B-meson mixing parameters in and beyond
the SM with 2 + 1 flavor lattice QCD
C.M. Boucharda,b, E.D. Freelandc, C.W. Bernardd , C.C. Change,f , A.X. El-Khadra∗ e ,
M.E. Gámizg , A.S. Kronfeldf,h , J. Laihoi, R.S. Van de Waterf
a
Department of Physics, The Ohio State University, Columbus, OH 43210, USA
of Physics, The College of William and Mary, Williamsburg, VA 23187, USA
c Liberal Arts Department, The School of the Art Institute of Chicago, Chicago, IL 60603, USA
d Department of Physics, Washington University, St. Louis, MO 63130, USA
e Physics Department, University of Illinois, Urbana, IL 61801, USA
f
Theoretical Physics Department, Fermi National Accelerator Laboratory,† Batavia, IL 60510,
USA
g CAFPE and Departamento de Fisica Teorica y del Cosmos, Universidad de Granada, E-18002
Granada, Spain
h Institute for Advanced Study, Technische Universität München, 85748 Garching, Germany
i Department of Physics, Syracuse University, Syracuse, NY 13244, USA
b Department
Fermilab Lattice and MILC Collaborations
We report on the status of our calculation of the hadronic matrix elements for neutral B-meson
mixing with asqtad sea and valence light quarks and using the Wilson clover action with the
Fermilab interpretation for the b quark. We calculate the matrix elements of all five local operators
that contribute to neutral B-meson mixing both in and beyond the Standard Model. We use MILC
ensembles with N f = 2 + 1 dynamical flavors at four different lattice spacings in the range a ≈
0.045–0.12 fm, and with light sea-quark masses as low as 0.05 times the physical strange quark
mass. We perform a combined chiral-continuum extrapolation including the so-called wrongspin contributions in simultaneous fits to the matrix elements of the five operators. We present a
complete systematic error budget and conclude with an outlook for obtaining final results from
this analysis.
The 32nd International Symposium on Lattice Field Theory
23-28 June, 2014
Columbia University New York, NY
∗ Speaker.
† Operated
by Fermi Research Alliance, LLC, under Contract No. DE-AC02-07CH11359 with the United States
Department of Energy
c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
http://pos.sissa.it/
ACT-13-14, MIFPA-14-39
arXiv:1412.5093v1 [hep-th] 16 Dec 2014
Helical Phase Inflation and Monodromy in Supergravity Theory
Tianjun Li ,1, 2 Zhijin Li,3 and Dimitri V. Nanopoulos3, 4, 5
1
State Key Laboratory of Theoretical Physics and Kavli Institute for Theoretical Physics China (KITPC),
Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China
2
School of Physical Electronics, University of Electronic Science
and Technology of China, Chengdu 610054, P. R. China
3
George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy,
Texas A&M University, College Station, TX 77843, USA
4
Astroparticle Physics Group, Houston Advanced Research Center (HARC),
Mitchell Campus, Woodlands, TX 77381, USA
5
Academy of Athens, Division of Natural Sciences,
28 Panepistimiou Avenue, Athens 10679, Greece
1
Abstract
We study helical phase inflation in supergravity theory in details. The inflation is driven by the
phase component of a complex field along helical trajectory. The helicoid structure originates from
the monodromy of superpotential with an singularity at origin. We show that such monodromy
can be formed by integrating out heavy fields in supersymmetric field theory. The supergravity
corrections to the potential provide strong field stabilizations for the scalars except inflaton, therefore the helical phase inflation accomplishes the “monodromy inflation” within supersymmetric
field theory. The phase monodromy can be easily generalized for natural inflation, in which the
super-Planckian phase decay constant is realized with consistent field stabilization. The phaseaxion alignment is fulfilled indirectly in the process of integrating out the heavy fields. Besides,
we show that the helical phase inflation can be naturally realized in no-scale supergravity with
SU (2, 1)/SU (2) × U (1) symmetry since the no-scale K¨
ahler potential provides symmetry factors of
phase monodromy directly. We also demonstrate that the helical phase inflation can reduce to the
shift symmetry realization of supergravity inflation. The super-Planckian field excursion is accomplished by the phase component, which admits no dangerous polynomial higher order corrections.
The helical phase inflation process is free from the UV-sensitivity problem, and it suggests that
inflation can be effectively studied in supersymmetric field theory close to the unification scale in
Grand Unified Theory and a UV-completed frame is not prerequisite.
PACS numbers: 04.65.+e, 04.50.Kd, 12.60.Jv, 98.80.Cq
2
Analytic Prediction of Baryonic Effects
from the EFT of Large Scale Structures
arXiv:1412.5049v1 [astro-ph.CO] 16 Dec 2014
Matthew Lewandowski1,2 , Ashley Perko1 , and Leonardo Senatore1,2
1
2
Stanford Institute for Theoretical Physics,
Stanford University, Stanford, CA 94306
Kavli Institute for Particle Astrophysics and Cosmology,
Physics Department and SLAC, Menlo Park, CA 94025
Abstract
The large scale structures of the universe will likely be the next leading source of cosmological
information. It is therefore crucial to understand their behavior. The Effective Field Theory of
Large Scale Structures provides a consistent way to perturbatively predict the clustering of dark
matter at large distances. The fact that baryons move distances comparable to dark matter allows
us to infer that baryons at large distances can be described in a similar formalism: the backreaction of
short-distance non-linearities and of star-formation physics at long distances can be encapsulated in
an effective stress tensor, characterized by a few parameters. The functional form of baryonic effects
can therefore be predicted. In the power spectrum the leading contribution goes as ∝ k 2 P (k),
with P (k) being the linear power spectrum and with the numerical prefactor depending on the
details of the star-formation physics. We also perform the resummation of the contribution of the
long-wavelength displacements, allowing us to consistently predict the effect of the relative motion
of baryons and dark matter. We compare our predictions with simulations that contain several
implementations of baryonic physics, finding percent agreement up to relatively high wavenumbers
such as k ' 0.3 h Mpc−1 or k ' 0.6 h Mpc−1 , depending on the order of the calculation. Our results
open a novel way to understand baryonic effects analytically, as well as to interface with simulations.
1
Introduction and Main Idea
After the completion of the data analyses of the Planck satellite, the next leading source of cosmological information will likely be large scale structure (LSS) surveys. The cosmological information that
we inherited from the WMAP and Planck missions raises the bar extremely high: in order for LSS to
be able to significantly improve our knowledge of the early universe, it is mandatory to understand
to percent level the behavior of the LSS observables. Order-of-magnitude understanding very rarely
will be useful. Since most of the modes are gathered at short distances, this means that we need to
understand the quasi-linear regime of structure formation. Recently, a research program called the
LAPTh–234/14
arXiv:1412.5016v1 [physics.comp-ph] 16 Dec 2014
LanHEP - a package for automatic generation of
Feynman rules from the Lagrangian. Updated
version 3.2
A. Semenov.
Joint Institute of Nuclear research, JINR, 141980 Dubna, Russia
and
Laboratoire de Physique Théorique LAPTh, Université de Savoie,
Chemin de Bellevue, B.P. 110, F-74941 Annecy-le-Vieux, Cedex, France.
Abstract
We present a new version 3.2 of the LanHEP software package. New features
include UFO output, color sextet particles and new substutution techniques which
allow to define new routines.
Introduction
The LanHEP program [1] is developed for Feynman rules generation from the Lagrangian.
It reads the Lagrangian written in a compact form, close to the one used in publications. It
means that Lagrangian terms can be written with summation over indices of broken symmetries and using special symbols for complicated expressions, such as covariant derivative
and strength tensor for gauge fields. Supersymmetric theories can be described using the
superpotential formalism and the 2-component fermion notation. The output is Feynman
rules in terms of physical fields and independent parameters in the form of CompHEP [2]
or CalcHEP [3] model files, which allows one to start calculations of processes in the new
physical model. Alternatively, Feynman rules can be generated in FeynArts [4] format or
as LaTeX table. The program can also generate one-loop counterterms in the FeynArts
format.
New version of the package can also generate Feynman rules in UFO [5] format. Use
command line option -ufo to select this format.
The package can be downloaded from
http://theory.sinp.msu.ru/~semenov/lanhep.html
1
Color sextets
One can use now particles belonging to 6-dimensional representation of the color SU(3)
group, color sextets. LanHEP name for this representation is color c6 (and color c6b
for anti-sextets), it can be used in the particle definition like:
scalar s6/S6:(’some sextet’, mass M6=100, color c6).
1
Heavy Quark Potential at Finite Temperature in a Dual Gravity
Closer to Large N QCD
arXiv:1412.5003v1 [hep-th] 16 Dec 2014
Binoy Krishna Patra and Himanshu Khanchandani
Department of Physics, Indian Institute of Technology Roorkee, India, 247 667
Abstract
In gauge-gravity duality, heavy quark potential at finite temperature is usually calculated with the pure AdS background, which does not capture the renormalisation group
(RG) running in the gauge theory part and the potential also does not contain any confining term in the deconfined phase. Following the developments in [39], a geometry was
contructed recently in [40, 43], which captures the RG flow similar to QCD and we employ
their geometry to obtain the heavy quark potential by analytically continuing the string
configurations into the complex plane. In addition to the attractive terms, the obtained potential has confining terms both at T = 0 and T 6= 0, compared to the calculations usually
done in the literature, where only Coulomb like term is present in the deconfined phase.
The potential also develops an (negative) imaginary part for above a critical separation,
rc (=0.53zh ). Moreover our potential exhibits a behaviour, different from the usual Debye
screening obtained from the pertubation theory.
PACS: 12.39.-x,11.10.St,12.38.Mh,12.39.Pn
Keywords: Heavy quark potential, Wilson loop, Thermal width, AdS/CFT, Nambu-Goto
Action
1
Introduction
The heavy quarks produced in the early stage of relativistic heavy-ion collisions (HIC) is one of
the cruical probes to the medium formed at later stage of the collision, known as quark-gluon
plasma (QGP). Matusi and Satz [1] first proposed the idea of Debye screening of the potential
between a heavy quark and a heavy antiquark, which causes the suppression of the yields of
heavy quarkonium states in HIC [2]. Since then many efforts have been devoted to understand
¯ states in the deconfined medium, using either the non-relativistic
the change of properties of QQ
1
Anomaly-induced effective action and Chern-Simons modification of
general relativity
Sebasti˜
ao Mauroa
arXiv:1412.5002v1 [gr-qc] 16 Dec 2014
(a)
and Ilya L. Shapirob,a,c
Departamento de F´ısica, ICE, Universidade Federal de Juiz de Fora,
CEP: 36036-330, Juiz de Fora, MG, Brazil
(b) Département de Physique Théorique and Center for Astroparticle Physics, Université de
Genève, 24 quai Ansermet, CH1211 Genéve 4, Switzerland
(c) Tomsk State Pedagogical University and Tomsk State University, Tomsk, 634041, Russia
Abstract. Recently it was shown that the quantum vacuum effects of massless
chiral fermion field in curved space-time leads to the parity-violating Pontryagin
density term, which appears in the trace anomaly with imaginary coefficient. In the
present work the anomaly-induced effective action with the parity-violating term is
derived. The result is similar to the Chern-Simons modified general relativity, which
was extensively studied in the last decade, but with the kinetic terms for the scalar
different from those considered previously in the literature. The parity-breaking term
makes no effect on the zero-order cosmology, but it is expected to be relevant in the
black hole solutions and in the cosmological perturbations, especially gravitational
waves.
Pacs: 04.62.+v, 11.10.Lm, 11.15.Kc
Keywords: Effective Action, Conformal anomaly, Chern-Simons gravity
1
Introduction
The derivation and properties of conformal (trace) anomaly are pretty well-known (see, e.g., [1]
and also [2, 3] for the technical introduction related to the present work). At the one-loop level
the anomaly is given by an algebraic sum of the contributions of massless conformal invariant
fields of spins 0, 1/2, 1 in a curved space-time of an arbitrary background metric. Recently, it
was confirmed that the quantum effects of chiral (L) fermion produce an imaginary contribution
which violates parity [4]. As a result, the anomalous trace has the form
˜ 2 − β4 P4 .
hTµµ i = − β1 C 2 − β2 E4 − a′ ✷R − βF
µν
(1)
Here we have included the external electromagnetic field Fµν = ∂µ Aν − ∂ν Aµ for generality, also
1 2
R
3
is the square of the Weyl tensor in four-dimensional space-time and
2
2
C 2 = Cµναβ C µναβ = Rµναβ
− 2Rαβ
+
E4 =
1 µναβ ρσλτ
2
2
ε
ε
Rµνρσ Rαβλτ = Rµναβ
− 4Rαβ
+ R2
4
(2)
(3)
Spectrum of three-body bound states in a finite volume
Ulf-G. Meißner,1, 2 Guillermo R´ıos,1 and Akaki Rusetsky1
1
Helmholtz-Institut f¨
ur Strahlen- und Kernphysik (Theorie) and Bethe
Center for Theoretical Physics, Universit¨
at Bonn, D-53115 Bonn, Germany
2
Institute for Advanced Simulation (IAS-4), Institut f¨
ur Kernphysik (IKP-3) and
J¨
ulich Center for Hadron Physics, Forschungszentrum J¨
ulich, D-52425 J¨
ulich, Germany
The spectrum of a bound state of three identical particles with a mass m in a finite cubic box is
studied. It is shown that in the unitary √
limit, the energy shift of a shallow bound state is given by
∆E = c(κ2 /m) (κL)−3/2 |A|2 exp(−2κL/ 3), where κ is the bound-state momentum, L is the box
size, |A|2 denotes the three-body analog of the asymptotic normalization coefficient of the bound
state wave function and c is a numerical constant. The formula is valid for κL ≫ 1.
PACS numbers: 11.10.St,11.80.Jy,12.38.Gc
INTRODUCTION
Strong interactions between two particles can be studied in ab initio lattice simulations, like for hadron-hadron
scattering in Quantum Chromodynamics or dimer-dimer scattering at ultracold temperatures. At present,
L¨
uscher’s approach [1] represents a standard way to study
two-body scattering observables on the lattice. In its
original form, this approach relates the two-particle scattering phase in the elastic region to the measured energy spectrum of the Hamiltonian in a finite volume.
In the literature, one finds different generalizations of
the L¨
uscher approach. For instance, the approach has
been formulated in case of moving frames [2], (partially)
twisted boundary conditions [3] and for coupled-channel
scattering [4] (for a recent application of this approach
to the analysis of the two-channel case on the lattice, see
Ref. [5]). A closely related framework based on the use of
the unitarized ChPT in a finite volume has been also proposed [6]. Further, a method for the measurement of resonance matrix elements and form factors in the time-like
region has been worked out [7]. Note, however that all
these generalizations explicitly deal with two-body channels. Studying a genuinely three-body problem in a finite
volume has proven to be a far more complicated enterprise and, albeit there have been several attempts to solve
this problem in the last few years [8–13], the method is
still in its infancy. On the other hand, recent progress on
the lattice, related to the study of the inelastic resonances
such as the Roper resonance [14], and of the properties
of light nuclei [15, 16], indicates that the generalization
of the L¨
uscher method to the multi-particle (three and
more) systems is urgently needed.
The main obstacle that one encounters in generalizing L¨
uscher’s approach from two to three particles has
a transparent physical interpretation. In the center-ofmass (CM) frame, the two-body scattering can be considered as a scattering of one particle in a given potential.
If this potential has a short range (much smaller than
the box size L), then the scattering wave function at the
boundaries will depend only on the scattering phase shift
in the infinite volume and, therefore, the discrete spectrum in a finite box will be determined by this phase shift
only. In other words, the spectrum in a large but finite
box does not depend on the details of interaction at short
distances. This is not so obvious in case of three particles.
In this case, each pair of particles can come close to each
other and be still separated from the third one by a large
distance of order L. It took a certain effort to prove that,
despite the fact that such configurations are allowed, the
finite-volume spectrum is still determined solely by the
infinite-volume S-matrix elements and does not depend
on the short-range details of the interaction [8], see also
Refs. [9, 10]. For instance, in a recent paper [9] the authors succeeded in deriving a quantization condition for
the three-particle spectrum in a finite volume. It has
a quite complicated structure, in particular, due to the
fact that the infinite-volume amplitudes that enter this
condition are defined in a unconventional manner (the necessity of such a definition has been pointed out already
in Ref. [8]). For this reason, it is not an easy task to use
this quantization condition for the analysis of lattice data
– in fact, we are not aware of a single explicit prediction
for the volume dependence of physical observables except
for the ground-state shift of identical particles [17], which
were done in this formalism so far [23]. Note also that in
Ref. [13], in the framework of the non-relativistic EFT,
It has been explicitly demonstrated that carrying out the
renormalization in the infinite volume leads to the cutoffindependent three-particle bound-state spectrum in a finite volume that is equivalent to the statement that this
spectrum is determined by the S-matrix elements in the
infinite volume.
The aim of the present paper is to obtain such an explicit volume dependence for the physical quantity which,
in our opinion, is the easiest to handle. In particular, we
consider shallow bound states of three identical particles
in the unitary limit. This means that the two-body scattering length a tends to infinity and the corresponding
effective range is zero. The three-body bound-state momentum κ, which is related to the binding energy ET
through ET = κ2 /m, is much smaller than the particle
AP-GR-118, OCU-PHYS-416, OU-HET-840, RIKEN-MP-98
Meson turbulence at quark deconfinement from AdS/CFT
Koji Hashimoto1,2 , Shunichiro Kinoshita3 , Keiju Murata4 , and Takashi Oka5
1
Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
Mathematical Physics Lab., RIKEN Nishina Center, Saitama 351-0198, Japan
3
Osaka City University Advanced Mathematical Institute, Osaka 558-8585, Japan
4
Keio University, 4-1-1 Hiyoshi, Yokohama 223-8521, Japan and
5
Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
arXiv:1412.4964v1 [hep-th] 16 Dec 2014
2
Based on the QCD string picture at confining phase, we conjecture that the deconfinement transition always accompanies a condensation of higher meson resonances with a power-law behavior,
“meson turbulence”. We employ the AdS/CFT correspondence to calculate the meson turbulence
for N = 2 supersymmetric QCD at large Nc and at strong coupling limit, and find that the energy
distribution to each meson level n scales as nα with the universal scaling α = −5. The universality
is checked for various ways to attain the quark deconfinement: a static electric field below/around
the critical value, a time-dependent electric field quench, and a time-dependent quark mass quench,
all result in the turbulent meson condensation with the universal power α = −5 around the deconfinement.
I.
TURBULENCE AND QUARK DECONFINEMENT
How the quarks are confined at the vacuum of quantum chromodynamics (QCD) is one of the most fundamental
questions in the standard model of particle physics. The question has attracted attention for long years, and recently
investigation has diverse approaches. The question is difficult simply because of the fact that the confinement appears
at the vacuum, not in a particular corner with specific external forces. Therefore, the confining vacuum can be broken
in various manner as one departs from the vacuum with the help of some external forces. The forces include for
example a finite temperature, a finite quark density and electric fields. Depending on how you break the vacuum
confinement, the resultant deconfined phases show various aspects with various global symmetries. This variety makes
the confinement problem even more difficult to be understood.
We would like to find a universal feature of the deconfinement. To understand the nature of the quark confinement,
we need a proper observable which exhibits a universal behavior irrespective of how we break the confinement. In
this paper, we propose a universal behavior of resonant mesons and name it meson turbulence.
As we have summarized in our letter [1], a particular behavior of resonant mesons (excited states of mesons) can be
an indicator of the deconfinement. The meson turbulence is a power-law scaling of the resonant meson condensations.
For the the resonant meson level n (n = 0, 1, 2, · · · ), the condensation of the meson hcn (x, t)i with its mass ωn causes
the n-th meson energy εn scaling as (ωn )α with a constant power α. This coefficient α will be unique for a given
theory, and does not depend on how one breaks the confinement. In particular, for the theory which we analyze in
this paper, that is N = 2 supersymmetric QCD with N = 4 supersymmetric Yang-Mills as its gluon sector at large
Nc at strong coupling, the universal power-law scaling parameter α is found to be
hεn i ∝ (ωn )α ,
α = −5 .
(1)
where εn is the energy of the n-th meson resonance. Normally, for example at a finite temperature, the energy stored
at the n-th level of the resonant meson should be a thermal distribution, εn ∝ exp[−ωn /T ]. The thermal distribution
is Maxwell-Boltzmann statistics, in which the higher (more massive) meson modes are exponentially suppressed.
However, we conjecture that this standard exponential suppression will be replaced by a power-law near any kind
of the deconfinement transitions. If we think of the meson resonant level n as a kind of internal momentum, then
the energy flow to higher n can be regarded as a so-called weak turbulence. This is why we call the phenomenon
meson turbulence, and the level n can be indeed regarded as a momentum in holographic direction in the AdS/CFT
correspondence [2–4].
The reason we came to the universal power behavior is quite simple. We combined two well-known things,
• Mesons are excitations of an open QCD string.
As is well-known, mesons and their resonant spectra are described by a quark model with a confining potential.
The confining potential has a physical picture of an open string whose end points are quarks. Rotating strings
can reproduce Regge behavior of the meson resonant spectra.
• Deconfinement phase is described by a condensation of long strings.
Mon. Not. R. Astron. Soc. 000, 000–000 (2014)
Printed 17 December 2014
(MN LATEX style file v2.2)
arXiv:1412.4905v1 [astro-ph.CO] 16 Dec 2014
Dark matter–radiation interactions: the impact on dark
matter haloes
J. A. Schewtschenko,1,2? R. J. Wilkinson,2 C. M. Baugh,1 C. Bœhm,2,3 S. Pascoli2 †
1 Institute
for Computational Cosmology, Durham University, Durham DH1 3LE, UK
for Particle Physics Phenomenology, Durham University, Durham DH1 3LE, UK
3 LAPTH, U. de Savoie, CNRS, BP 110, 74941 Annecy-Le-Vieux, France
2 Institute
17 December 2014
ABSTRACT
Interactions between dark matter (DM) and radiation (photons or neutrinos) in the
early Universe suppress density fluctuations on small mass scales. Here we perform
a thorough analysis of structure formation in the fully non-linear regime using N body simulations for models with DM–radiation interactions and compare the results
to a traditional calculation in which DM only interacts gravitationally. Significant
differences arise due to the presence of interactions, in terms of the number of lowmass DM haloes and their properties, such as their spin and density profile. These
differences are clearly seen even for haloes more massive than the scale on which
density fluctuations are suppressed. We also show that semi-analytical descriptions
of the matter distribution in the non-linear regime fail to reproduce our numerical
results, emphasizing the challenge of predicting structure formation in models with
physics beyond collisionless DM.
Key words: astroparticle physics – dark matter – galaxies: haloes – large-scale
structure of Universe.
1
INTRODUCTION
Dark matter (DM) is the most dominant and yet most elusive component of matter in the Universe. Exploring its nature is therefore one of the greatest challenges in both cosmology and particle physics today. The usual treatment of
DM in structure formation calculations neglects possible interactions between DM and other species. Yet if DM is a
(thermal) weakly interacting massive particle (WIMP), interactions (and more precisely, annihilations) are essential to
obtain the correct relic density. It is therefore important to
study the impact of DM interactions on other cosmological
observables.
It has been already established that a DM coupling with
primordial radiation, i.e. photons (Boehm et al. 2001, 2002;
Sigurdson et al. 2004; Boehm & Schaeffer 2005; Dolgov et al.
2013; Wilkinson et al. 2014a) or neutrinos (Boehm et al.
2001, 2002; Boehm & Schaeffer 2005; Mangano et al. 2006;
Serra et al. 2010; Wilkinson et al. 2014b) leaves a characteristic imprint on the CMB temperature and polarization
power spectra. In addition, in a previous publication (Boehm
?
† Also visiting Instituto de F´ısica Te´
orica, IFT-UAM/CSIC, Universidad Aut´
onoma de Madrid, Cantoblanco, 28049, Madrid,
Spain
et al. 2014), we showed using N -body simulations that such
interactions have a significant impact on the Milky Way environment, dramatically reducing the number of DM subhaloes that could potentially host satellite galaxies1 . Since
they have the potential to alleviate the small-scale problems
that have persisted in the standard cold DM (CDM) model
for more than a decade (Moore et al. 1999; Klypin et al.
1999; Boylan-Kolchin et al. 2011), these interactions should
not be ignored.
We now go a step further and study the abundance and
properties, such as shape, spin and density profile of collapsed DM structures in the presence of DM–radiation interactions. We highlight the differences with respect to CDM
and in addition, warm DM (WDM), which shows a qualitatively similar suppression of power on small scales (Schaeffer
& Silk 1988). We note that recent work has also considered
non-linear structure formation in a number of alternative
models such as self-interacting DM (Rocha et al. 2013; Vogelsberger et al. 2014), decaying DM (Wang et al. 2014),
late-forming DM (Agarwal et al. 2014), atomic DM (CyrRacine & Sigurdson 2013) and DM interacting with dark
radiation (Buckley et al. 2014; Chu & Dasgupta 2014); see
also Schneider (2014).
1
See also Bertoni et al. (2014).
TUM-HEP-971-14
arXiv:1412.4893v1 [hep-th] 16 Dec 2014
Feynman Diagrams for Stochastic Inflation and
Quantum Field Theory in de Sitter Space
Björn Garbrechta , Florian Gautiera , Gerasimos Rigopoulosb and Yi Zhua
a
Physik Department T70, James-Franck-Straße,
Technische Universität M¨
unchen, 85748 Garching, Germany
b
Institut f¨
ur Theoretische Physik, Philosophenweg 12,
Universität Heidelberg, 69120 Heidelberg, Germany
Abstract
We consider a massive scalar field with quartic self-interaction λ/4! φ4 in de Sitter
spacetime and present a diagrammatic expansion that describes the field as driven
by stochastic noise. This is compared with the Feynman diagrams in the Keldysh
basis of the Amphichronous (Closed-Time-Path) Field Theoretical formalism. For
all orders in the expansion, we find that the diagrams agree when evaluated in the
leading infrared approximation, i.e. to leading order in m2 /H 2 , where m is the
mass of the scalar field and H is the Hubble rate. As a consequence, the correlation
functions computed in both approaches also agree to leading infrared order. This
perturbative correspondence shows that the stochastic Theory is exactly equivalent
to the Field Theory in the infrared. The former can then offer a non-perturbative
resummation of √
the Field Theoretical Feynman diagram expansion, including fields
2
with 0 ≤ m ≪ λH 2 for which the perturbation expansion fails at late times.
1
Introduction
The stochastic approach to Inflation [1, 2] is a simple and effective framework that can
be used in order to evaluate correlation functions of scalar fields in de Sitter space on
scales exceeding the horizon. It can be derived from the underlying Field Theoretical
formulation, by treating the short-wavelength modes as quantum noise to the horizonsize field which is described as a classical random variable. This is justified by the
fact that the canonical commutator (between the field and the canonical momentum)
estimated within the stochastic framework is small compared to the anti-commutator,
i.e. by the usual criterion for the classical behaviour of a dynamic system. The resulting
random walk of the scalar field (on top of the solution to the deterministic equation of
motion) does not only offer valuable intuition for understanding the field evolution and
the emergence of classical stochastic perturbations in the Universe, it is also useful in
NT@UW-14-25
The return of nucleon strangeness?
T. J. Hobbs1 , Mary Alberg1,2 , Gerald A. Miller1
1
Department of Physics, University of Washington, Seattle, Washington 98195, USA
2
Department of Physics, Seattle University, Seattle, Washington 98122, USA
Determining the nonperturbative s¯
s content of the nucleon has attracted considerable interest
and been the subject of numerous experimental searches. These measurements used a variety of
reactions and place important limits on the vector form factors observed in parity-violating PV
elastic scattering and the parton distributions of deep inelastic scattering, DIS. In spite of this
progress, attempts to relate information obtained from elastic and DIS experiments have been
sparse. To ameliorate this situation, we develop an interpolating model using light-front wave
functions capable of computing both DIS and elastic observables. This framework is used to show
that existing knowledge of DIS places significant restrictions on our wave function. The result is
that the predicted effects of nucleon strangeness on elastic observables is much smaller than those
tolerated by direct fits to PV elastic scattering data alone. In particular, we find the narrow limits
−0.024 ≤ µs ≤ 0.035, and −0.137 ≤ ρD
s ≤ 0.081 for the strange contributions to the nucleon
magnetic moment and charge radius using our model, which are about ten times smaller than
previous bounds.
Spectroscopy of SU(4) lattice gauge theory with
fermions in the two index anti-symmetric
representation
Thomas DeGrand1 , Yuzhi Liu1∗ and Ethan T. Neil1,2
1 Department
of Physics, University of Colorado, Boulder, CO 80309, USA
Research Center, Brookhaven National Laboratory, Upton, NY USA
Email: [email protected], [email protected],
[email protected]
2 RIKEN-BNL
Yigal Shamir and Benjamin Svetitsky
Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, 69978
Tel Aviv, Israel
Email: [email protected], [email protected]
We present a study of spectroscopy of SU(4) lattice gauge theory coupled to two flavors of Dirac
fermions in the anti-symmetric two index representation. The fermion representation is real,
and the pattern of chiral symmetry breaking is SU(2N f ) → SO(2N f ) with N f flavors of Dirac
fermions. It is an interesting generalization of QCD, for several reasons: it allows direct exploration of an alternate large Nc expansion, it can be simulated at non-zero chemical potential with
no sign problem, and several UV completions of composite Higgs systems are built on it. We
present preliminary results on the baryon and meson spectra of the theory and compare them with
SU(3) results and with expectations for large Nc scaling.
The 32nd International Symposium on Lattice Field Theory,
23-28 June, 2014
∗ Speaker.
Yuzhi Liu1
SU(4) sextet spectrum
1. Introduction
The authors of this paper are involved in a diverse set of projects involving SU (4) gauge theory
with various numbers of flavors of degenerate mass fermions in the two-index antisymmetric (AS2)
representation of the gauge group, which is a sextet for SU (4). These systems are interesting for a
variety of reasons:
First, they are confining and chirally broken systems with similarities to ordinary Nc = 3 QCD.
In fact, there is an alternate large-Nc limit of ordinary QCD in which the fermions live in an AS2
representation. For Nc = 3, AS2 quarks inhabit the 3¯ representation. The story goes back to [1]. It
reappears in more modern guises in, for example, [2, 3]. Lattice simulation can test the expected
large-Nc regularities, as it has for the usual ’t Hooft limit of fixed N f fundamental representation
fermions at varying Nc . (An assortment of recent results includes [4, 5].)
Next, they form a chirally broken system with some differences compared to ordinary Nc = 3
QCD. Because the fermions are in a real representation of the gauge group, the pattern of chiral
symmetry breaking is not SU (N f ) ⊗ SU (N f ) → SU (N f ); it is SU (2N f ) → SO(2N f ) (all for N f
flavors of Dirac fermions) [6]. The reality of the representation allows quarks and antiquarks to
mix under global flavor rotations. In particular, the N f = 2 theory has nine Goldstone bosons,
which may be classified as isospin I = 1 triplets of qq,
¯ qq, and q¯q.
¯
Third, reality of the representation means that finite density simulations do not suffer from a
sign problem. This is similar to the situation for Nc = 2 with fundamental representation fermions
[7]. There is a literature of predictions for SU (4) [8], which we can explore.
Finally, members of this family play a role in composite Higgs studies. For example, the
Littlest Higgs model [9] relies on the non-linear sigma model SU (5)/SO(5). Examples of proposed
SU (4) UV completions of composite Higgs models, mostly involving 5 Majorana fermions, are
given in Refs. [10].
In this note we describe results relevant to the first of these points. The details of the calculations will be presented in our longer paper [11].
2. Lattice setup and observables
We use the usual Wilson plaquette gauge action and Wilson-clover fermions with nHYP
smeared links as the gauge connections. The bare gauge coupling g is defined through β = 2Nc /g2 .
The bare quark mass m is introduced through the hopping parameter κ . The clover coefficient is
fixed at its tree level value, csw = 1.
Simulations were done at four different κ values at a bare coupling β = 9.6. The lattice volume
is fixed to be 163 × 32. In addition, we calculated spectroscopy at four more partially quenched
(PQ) points based on one dynamical data set.
Our large-Nc comparisons are done against simulations of SU (3) gauge theory with N f = 2
fundamental fermions. Five different κ values were used at one fixed gauge coupling. Previously
generated quenched SU (Nc ) theories, with Nc = 3, 5, and 7 are also used for comparison [12]. All
these data sets had the same volume, 163 × 32. For comparison among different theories, we fix the
lattice spacings using r1 , the shorter version [13] of the Sommer [14] parameter, defined in terms
of the force F(r) between static quarks: r2 F(r) = −1.0 at r = r1 .
2
CERN-PH-TH-2014-193
arXiv:1412.4828v1 [gr-qc] 15 Dec 2014
Phenomenology of theories of gravity
without Lorentz invariance:
the preferred frame case∗
Diego Blas[†, Eugene Lim]‡
[
CERN, Theory Division, 1211 Geneva, Switzerland.
]
Theoretical Particle Physics and Cosmology Group,
Physics Department, Kings College London, Strand, London WC2R 2LS, United Kingdom
December 17, 2014
Abstract
Theories of gravitation without Lorentz invariance are candidates of low-energy
descriptions of quantum gravity. In this review we will describe the phenomenological
consequences of the candidates associated to the existence of a preferred time direction.
∗
Invited contribution to the special issue “Modified Gravity and Effects of Lorentz Violation” to appear
in IJMPD.
†
[email protected]
‡
[email protected]
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
Charmed baryonic resonances in medium
Laura Tolos1,2, a
1
Instituto de Ciencias del Espacio (IEEC/CSIC), Campus Universitat Autònoma de Barcelona, Facultat de
Ciències, Torre C5, E-08193 Bellaterra (Barcelona), Spain
2
Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe University, Ruth-Moufang-Str. 1, 60438
Frankfurt am Main, Germany
Abstract. We discuss the behavior of dynamically-generated charmed baryonic resonances in matter within a unitarized coupled-channel model consistent with heavy-quark
spin symmetry. We analyze the implications for the formation of D-meson bound states
in nuclei and the propagation of D mesons in heavy-ion collisions from RHIC to FAIR
energies.
1 Introduction
Quantum Chromodynamics (QCD) is the basic theory of the strong interaction. In the low-energy
regime, QCD becomes a strongly-coupled theory, many aspects of which are not yet understood. An
important effort has been invested in exploring the QCD phase diagram for high density and/or temperature. In fact, the study of matter under extreme conditions has become one of the main research
activities of several experimental programs, from the ongoing LHC/CERN (Switzerland) [1] to the
forthcoming FAIR (Germany) [2] projects. Until now the studies have been concentrated in matter
within the light-quark sector due to energy constraints. With the on-going and upcoming research
facilities, the aim is to move from the light-quark domain to the heavy-quark one and to face new
challenges where charm and new symmetries, such as heavy-quark symmetry, will play a significant
role.
The primary theoretical effort is to understand the interaction between hadrons that incorporate
the charm degree of freedom. With data coming from CLEO, Belle, BaBar [3] and other experiments,
charmed hadronic states have received a lot of attention. Moreover, it is expected that in the upcoming
years the FAIR project will provide new insights on charmed hadron spectroscopy [2]. The ultimate
goal is to understand whether these states can be understood within the quark model picture and/or
qualify better as dynamically generated states via hadron-hadron scattering processes.
There has been a tremendous success in describing experimental data on hadron spectroscopy by
means of approaches based on coupled-channel dynamics. Particularly, unitarized coupled-channel
methods have been used in the meson-baryon sector with charm content [4–21], mostly motivated by
the parallelism between the Λ(1405) and the Λc (2595).
However, some of these models are not fully consistent with heavy-quark spin symmetry (HQSS)
[22]. HQSS is a proper QCD symmetry that appears when the quark masses become larger than
a e-mail: [email protected]
CERN-PH-TH-2014-242
Gauged R-symmetry and its anomalies
arXiv:1412.4807v1 [hep-th] 15 Dec 2014
in 4D N=1 supergravity and phenomenological implications
I. Antoniadis a,b,c , D. M. Ghilencea d,e , R. Knoopsd, f
a
Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics,
University of Bern, 5 Sidlestrasse, CH-3012 Bern, Switzerland
b
LPTHE, Universite Pierre et Marie Curie, F-75252 Paris, France
c
d
e
Ecole Polytechnique, F-91128 Palaiseau, France
CERN Theory Division, CH-1211 Geneva 23, Switzerland
Theoretical Physics Department, National Institute of Physics and
Nuclear Engineering (IFIN-HH) Bucharest, MG-6 077125, Romania.
f
Instituut voor Theoretische Fysica, KU Leuven, Clestijnenlaan 200D, B-3001 Leuven, Belgium
Abstract
We consider a class of models with gauged U (1)R symmetry in 4D N=1 supergravity that
have, at the classical level, a metastable ground state, an infinitesimally small (tunable)
positive cosmological constant and a TeV gravitino mass. We analyse if these properties
are maintained under the addition of visible sector (MSSM-like) and hidden sector state(s),
where the latter may be needed for quantum consistency. We then discuss the anomaly
cancellation conditions in supergravity as derived by Freedman, Elvang and Körs and apply
their results to the special case of a U (1)R symmetry, in the presence of the Fayet-Iliopoulos
term (ξ) and Green-Schwarz mechanism(s). We investigate the relation of these anomaly
cancellation conditions to the “naive” field theory approach in global SUSY, in which case
U (1)R cannot even be gauged. We show the two approaches give similar conditions. Their
induced constraints at the phenomenological level, on the above models, remain strong even
if one lifted the GUT-like conditions for the MSSM gauge couplings. In an anomaly-free
model, a tunable, TeV-scale gravitino mass may remain possible provided that the U (1)R
charges of additional hidden sector fermions (constrained by the cubic anomaly alone) do not
conflict with the related values of U (1)R charges of their scalar superpartners, constrained
by existence of a stable ground state. This issue may be bypassed by tuning instead the
coefficients of the Kahler connection anomalies (bK , bCK ).
Bridging a gap between continuum-QCD and ab initio predictions of hadron observables
Daniele Binosia , Lei Changb , Joannis Papavassiliouc, Craig D. Robertsd
a
European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT∗ ) and Fondazione Bruno Kessler
Villa Tambosi, Strada delle Tabarelle 286, I-38123 Villazzano (TN) Italy
b CSSM, School of Chemistry and Physics University of Adelaide, Adelaide SA 5005, Australia
c Department of Theoretical Physics and IFIC, University of Valencia and CSIC, E-46100, Valencia, Spain
d Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
Abstract
Preprint no. ADP-14-42/T901
Within contemporary hadron physics there are two common methods for determining the momentum-dependence of the interaction
between quarks: the top-down approach, which works toward an ab initio computation of the interaction via direct analysis of the
gauge-sector gap equations; and the bottom-up scheme, which aims to infer the interaction by fitting data within a well-defined
truncation of those equations in the matter sector that are relevant to bound-state properties. We unite these two approaches by
demonstrating that the renormalisation-group-invariant running-interaction predicted by contemporary analyses of QCD’s gauge
sector coincides with that required in order to describe ground-state hadron observables using a nonperturbative truncation of
QCD’s Dyson-Schwinger equations in the matter sector. This bridges a gap that had lain between nonperturbative continuum-QCD
and the ab initio prediction of bound-state properties.
Keywords: Dyson-Schwinger equations, confinement, dynamical chiral symmetry breaking, fragmentation, Gribov copies
1. Introduction. The last two decades have seen significant
progress and phenomenological success in the formulation and
use of symmetry preserving methods in continuum-QCD for
the computation of observable properties of hadrons [1–8]. A
large part of that work is based on the rainbow-ladder (RL) truncation of QCD’s Dyson-Schwinger equations (DSEs), which
is the leading-order term in a symmetry preserving approximation scheme [9, 10]. The RL truncation is usually employed with a one-parameter model for the infrared behaviour
of the quark-quark interaction produced by QCD’s gauge-sector
[11, 12]. It is accurate for ground-state vector- and isospinnonzero pseudoscalar-mesons constituted from light quarks and
also for nucleon and ∆ properties because corrections in all
these channels largely cancel owing to parameter-free preservation of the Ward-Green-Takahashi (WGT) identities [13–16].
Corrections do not cancel in other channels, however; and
hence studies based on the RL truncation, or low-order improvements thereof [17, 18], have usually provided poor results
for all other systems.
A recently developed truncation scheme [19] overcomes the
weaknesses of RL truncation in all channels considered thus
far. This new strategy, too, is symmetry preserving but it has an
additional strength; namely, the capacity to express dynamical
chiral symmetry breaking (DCSB) nonperturbatively in the integral equations connected with bound-states. That is a crucial
advance because, like confinement, DCSB is one of the most
important emergent phenomena within the Standard Model: it
may be considered as the origin of more than 98% of the visible
mass in the Universe. Owing to this feature, the new scheme is
described as the DB truncation. It preserves successes of the RL
truncation but has also enabled a range of novel nonperturbative
Preprint submitted to Physics Letters B
features of QCD to be demonstrated [20–23].
The widespread phenomenological success of this bottom-up
approach to the calculation of hadron observables raises an important question; viz., are the one-parameter RL or DB interaction models, used in those equations relevant to colour-singlet
bound-states, consistent with modern analyses of QCD’s gauge
sector and the solutions of the gluon and ghost gap equations
they yield [24–34]? An answer in the affirmative will grant significant additional credibility to the claim that these predictions
are firmly grounded in QCD.
2. Quark gap equation. In order to expose the computational
essence of the bottom-up DSE studies, it is sufficient to consider the gap equation for the dressed quark Schwinger function, S (p) = Z(p2 )/[iγ · p + M(p2 )]:
S −1 (p) = Z2 (iγ · p + mbm ) + Σ(p) ,
Z Λ
λa
λa
Σ(p) = Z1
g2 Dµν (p − q) γµ S (q) Γν (q, p),
2
2
dq
(1a)
(1b)
where: Dµν is the gluon propagator;1 Γν , the quark-gluon verRΛ
tex; dq , a symbol representing a Poincaré invariant regularisation of the four-dimensional integral, with Λ the regularisation mass-scale; mbm (Λ), the current-quark bare mass; and
1 Landau gauge is typically used because it is, inter alia [35–37]: a fixed
point of the renormalisation group; that gauge for which sensitivity to modeldependent differences between Ansätze for the fermion–gauge-boson vertex are
least noticeable; and a covariant gauge, which is readily implemented in numerical simulations of lattice regularised QCD. Importantly, capitalisation on the
gauge covariance of Schwinger functions obviates any question about the gauge
dependence of gauge invariant quantities.
11 December 2014
Photon-photon refraction for TeV gamma rays
Alexandra Dobrynina,1, 2 Alexander Kartavtsev,2 and Georg Raffelt2
arXiv:1412.4777v1 [astro-ph.HE] 15 Dec 2014
2
1
P. G. Demidov Yaroslavl State University, Sovietskaya 14, 150000 Yaroslavl, Russia
Max-Planck-Institut f¨
ur Physik (Werner-Heisenberg-Institut), F¨
ohringer Ring 6, 80805 M¨
unchen, Germany
(Dated: 15 December 2014)
The propagation of TeV gamma rays can be strongly modified by B-field induced conversion
to axion-like particles. The conversion rate depends on the photon dispersion relation which, at
such high energies, is dominated by the B field itself through the QED photon-photon interaction.
However, ambient photons also contribute and the cosmic microwave background (CMB) dominates
when B < 3.25 µG. We determine the photon-photon refractive index for all energies and find that,
in intergalactic space, the CMB dominates for dispersion, whereas for absorption by γγ → e+ e−
it is the extra-galactic background light. Local radiation fields, e.g., the galactic star light, can be
more important for dispersion than the CMB.
PACS numbers: 95.85.Pw, 98.70.Rz, 14.70.Bh, 14.80.Va
Introduction.—Astronomy with TeV gamma rays has
opened a new window to the universe, allowing us to
study a plethora of fantastic sources of very high-energy
photons [1–5]. In addition to the sources themselves,
we can study intervening phenomena. In particular, the
radiation emitted by all stars, the extra-galactic background light (EBL), is an important opacity source by
γγ → e+ e− . As a result, the TeV gamma-ray horizon
is only some 100 Mpc and the observed source spectra
are strongly modified. We can use this effect to explore
the EBL which is difficult to measure directly [6]. More
fundamentally, the fast time structure of certain sources
allows us to constrain novel dispersion effects, for example by hypothetical Lorentz invariance violation [7, 8].
We are here concerned with another effect at the lowenergy frontier of elementary particle physics [9–12], the
conversion of photons into axion-like particles (ALPs) in
large-scale magnetic fields [13, 14], enabled by the twophoton vertex of these hypothetical low-mass spin-zero
bosons. The conversion γ → a modifies the source spectra and the conversion and subsequent back-conversion
γ → a → γ allows TeV gamma rays to “propagate in
disguise” and evade absorption by e+ e− pair production
[15–38]. This effect is a possible explanation of the cosmic transparency problem, i.e., TeV gamma rays seem to
travel further than allowed by typical EBL estimates. At
the very least, this effect represents a systematic uncertainty when probing the EBL with TeV gamma rays.
Photon and ALP propagation and conversion is most
easily studied in analogy to neutrino flavor oscillations
[14, 39]. A wave of frequency ω and amplitude A evolves
in the x direction according to −i∂x A = nrefr ω A, where
nrefr is the refractive index which gives us the wave number by k = nrefr ω. We write nrefr = 1 + χ + iκ and
assume |χ + iκ| ≪ 1. The real part χ describes dispersion and the imaginary part κ absorption. A has three
components, the photon amplitude A⊥ with polarization
perpendicular to the transverse B-field, Ak parallel to
it, and the ALP amplitude a, i.e., A = (A⊥ , Ak , a), and
χ and κ are now 3×3 matrices. The off-diagonal χ elements cause oscillations between different A-components
such as the Faraday effect, where electrons in the longitudinal B field couple the linear photon polarization states
and thus instigate a rotation of the plane of polarization.
ALPs interact with photons by Laγ = gaγ E · B a in
terms of the electric, magnetic and ALP fields and gaγ
is a coupling constant of dimension inverse energy. An
external transverse magnetic field BT couples Ak with
a and provides an off-diagonal refractive index χaγ =
gaγ BT /2ω which leads to ALP-photon oscillations. (We
always use natural units with ~ = c = kB = 1.) The
ALP dispersion relation is ω 2 − k 2 = m2a , providing
the refractive index χa = −m2a /2ω 2 . An analogous expression pertains to photons with the plasma frequency
2
= 4παne /me ; its modification by an assumed B-field
ωpl
causes the Faraday effect.
More important for TeV gamma ray dispersion is the
B field itself due to an effective photon-photon interaction mediated by virtual e+ e− pairs. At low energies, it is described by the Euler-Heisenberg Lagrangian
Lγγ = (2α2 /45m4e ) [(E2 − B2 )2 + 7(E · B)2 ]. However,
this interaction also pertains to background photons, not
just static fields. The overall electromagnetic (EM) energy density ρEM = 21 hE 2 + B 2 i produces [40–45]
χEM =
44α2 ρEM
,
135 m4e
(1)
implying space-like dispersion ω 2 − k 2 = −2χEMω 2 .
Large-scale fields or non-isotropic background photons
imply further geometrical factors depending on direction
of motion and polarization. If the EM background is
a homogeneous B-field, the dispersion of Ak receives a
factor (14/11) sin2 θ, whereas A⊥ a factor (8/11) sin2 θ
[45–49]. Here, θ is the angle between the photon and
B-field directions, i.e., only the transverse field strength
enters. These results correspond to what has been used
in studies of TeV gamma ray propagation.
CP3-Origins-2014-045 DNRF90
DIAS-2014-45
Scattering lengths in SU(2) gauge theory with two
fundamental fermions
R. Arthur a , V. Drach∗a , M. Hansen a, A. Hietanen a , C. Pica a , F. Sannino a
aCP3 -Origins
& the Danish Institute for Advanced Study DIAS, University of Southern Denmark,
Campusvej 55, DK-5230 Odense M, Denmark
We investigate non perturbatively scattering properties of Goldstone Bosons in an SU(2) gauge
theory with two Wilson fermions in the fundamental representation. Such a theory can be used to
build extensions of the Standard Model that unifies Technicolor and pseudo Goldstone composite
Higgs models. The leading order contribution to the scattering amplitude of Goldstone bosons
at low energy is given by the scattering lengths. In the context of technicolor extensions of the
Standard Model the scattering lengths are constrained by WW scattering measurements. We first
describe our setup and in particular the expected chiral symmetry breaking pattern. We then
discuss how to compute them on the lattice and give preliminary results using finite size methods.
The 32nd International Symposium on Lattice Field Theory,
23-28 June, 2014
∗ Speaker.
Scattering lengths in a Composite Higgs Model
V. Drach
1. Introduction
In this work we consider an SU (2) gauge field theory with two fermions in the fundamental
representation. The Lagrangian reads in the continuum :
1 a a µν
L = − Fµν
F
+ ψ (i6D − m) ψ ,
4
(1.1)
where ψ = (u, d) is a doublet of Dirac spinor fields transforming according to the fundamental
representation.
Because of the pseudo-realness of the fundamental representation of SU (2), the mass term of
the Lagrangian can be written in terms of 4 Weyl spinors as follows1
†
im
1 a a µν
F
+ ψ i6Dψ + QT (−iσ2 )CEQ + QT (−iσ2 )CEQ)
L = − Fµν
4
2
(1.2)
where σ2 acts on color indices and C is the charge conjugation matrix. Furthermore, we have
defined :

uL

 d


L
Q=
 , and
−iσ2Cu¯TR 
−iσ2Cd¯T

R

0
0

E =
−1
0
0
0
0
−1
+1
0
0
0

0
+1

.
0
0
(1.3)
We have used qL,R = PL,R q, q¯L,R = qP
¯ R,L with PL = 12 (1 − γ5 ) and PR = 21 (1 + γ5 ). The model
exhibits an SU (4) flavour symmetry in the massless limit. To fix notations, the 15 generators of
the corresponding Lie algebra will be denoted T a=1,...,15 . After adding a mass term, the remnant
flavour symmetry is the group spanned by the algebra that preserves ET a,T + T a,T E = 0. This
relation defines the 10-dimensional algebra of the SP(4) group. The chiral symmetry breaking
pattern is thus expected to be SU (4) → SP(4) leading to 5 Goldstone bosons.
As proposed in [2], the Lagrangian Eq. (1.1) can be embedded into the Standard Model in such
a way that it interpolates between composite Goldstone Higgs and Technicolor models[3, 4].
The model has been investigated on the lattice in [5], and the chiral symmetry breaking pattern
has been proven to be the expected one [6]. Updated results concerning our on-going effort are
summarized in [7].
Since one feature of the model is to provide a dynamical explanation of Electroweak symmetry breaking, calculating the scattering properties of the Goldstone bosons of the underlying
theory can be related to scattering properties of longitudinal W bosons according to the equivalence theorem[8].
The two particle states involving two Goldstone bosons can be classified according 5 ⊗ 5 =
1 ⊕ 10 ⊕ 14 and it can be shown that π + π + belongs to the 14 dimensional representation of SP(4).
The low energy prediction for this realization of chiral symmetry breaking has been considered
in[9], and reads:
m2PS
mPS a14
(1.4)
0,LO = −
2
32 fPS
1 In
fact SU(2) is the first of the Sp(2N) gauge theories. The associated conformal window was studied in [1].
2
Precision nucleon-nucleon potential at fifth order in the chiral expansion
E. Epelbaum,1 H. Krebs,1 and U.-G. Meißner2, 3, 4
1
Institut f¨
ur Theoretische Physik II, Ruhr-Universit¨
at Bochum, D-44780 Bochum, Germany
Helmholtz-Institut f¨
ur Strahlen- und Kernphysik and Bethe Center for Theoretical Physics,
Universit¨
at Bonn, D-53115 Bonn, Germany
3
Institut f¨
ur Kernphysik, Institute for Advanced Simulation,
and J¨
ulich Center for Hadron Physics, Forschungszentrum J¨
ulich, D-52425 J¨
ulich, Germany
4
JARA - High Performance Computing, Forschungszentrum J¨
ulich, D-52425 J¨
ulich, Germany
2
We present a nucleon-nucleon potential at fifth order in chiral effective field theory. We find
a substantial improvement in the description of nucleon-nucleon phase shifts as compared to the
fourth-order results of Ref. [1]. This provides clear evidence of the corresponding two-pion exchange
contributions with all low-energy constants being determined from pion-nucleon scattering. The
fifth-order corrections to nucleon-nucleon observables appear to be of a natural size which confirms
the good convergence of the chiral expansion for nuclear forces. Furthermore, the obtained results
provide strong support for the novel way of quantifying the theoretical uncertainty due to the
truncation of the chiral expansion proposed in Ref. [1]. Our work opens up new perspectives for
precision ab initio calculations in few- and many-nucleon systems and is especially relevant for
ongoing efforts towards a quantitative understanding the structure of the three-nucleon force in the
framework of chiral effective field theory.
PACS numbers: 13.75.Cs,21.30.-x
Chiral effective field theory (EFT) provides a solid
foundation for analyzing low-energy hadronic observables
in harmony with the symmetries of quantum chromodynamics (QCD), the underlying theory of the strong interactions. It allows one to derive nuclear forces and currents in a systematically improvable way order by order
in the chiral expansion, based on a perturbative expansion in powers of Q ∈ (p/Λb , Mπ /Λb ), where p refers to
the magnitude of three momenta of the external particles, Mπ is the pion mass and Λb is the breakdown scale
of chiral EFT [2]. Being combined with modern few- and
many-body methods, the resulting framework based on
solving the nuclear A-body Schr¨
odinger equation with interactions between nucleons tied to QCD via its symmetries represents nowadays a commonly accepted approach
to ab initio studies of nuclear structure and reactions, see
Refs. [3, 4] for review articles.
Chiral power counting suggests that nuclear forces are
dominated by pairwise interactions between the nucleons [2], a feature that was known for long but could
only be explained with the advent of chiral EFT. Manybody forces are suppressed by powers of the expansion parameter Q. Specifically, the chiral expansion of
nucleon-nucleon (NN), three-nucleon (3NF) and fournucleon (4NF) forces starts at the orders Q0 (LO), Q3
(N2 LO) and Q4 (N3 LO), respectively, while next-toleading (NLO) corrections involve two-body operators
only. While accurate NN potentials at N3 LO have been
available for about a decade [5, 6], the 3NF still represents
one of the major challenges in the physics of nuclei and
nuclear matter [7]. In particular, numerically exact calculations in the three-nucleon (3N) continuum, the most
natural place to test the 3NF, have revealed that the
spin-structure of the 3NF is not properly reproduced by
the available models [8]. Specifically, one observes clear
discrepancies between theory and experimental data for
various spin observables in nucleon-deuteron (Nd) scattering starting at EN ∼ 50 MeV which tend to increase
with energy. In addition, there are a few discrepancies at
low energies such as e.g. the so-called Ay -puzzle, see [8]
for more details.
In the framework of chiral EFT, the impact of the leading 3NF at N2 LO on three- and four-nucleon scattering,
nuclear structure and reactions as well as nuclear matter
has been extensively studied using different many-body
techniques. In particular, the N2 LO 3NF was found to
reduce the discrepancy for Ay in proton-3 He elastic scattering [9], to play a crucial role in understanding neutronrich systems [10] and the properties of neutron and nuclear matter, see [7] and references therein. Lattice simulations of light nuclei within the framework of chiral
EFT also confirm the important role of the N2 LO 3NF
[11–13]. On the other hand, the Ay puzzle in elastic Nd
scattering is not resolved at N2 LO [9], and the existing
discrepancies for spin observables in the 3N continuum
at medium and higher energies are beyond the expected
theoretical accuracy at this order. It is, therefore, necessary to study corrections beyond the leading 3NF. The
N3 LO contributions to the 3NF have been worked out
recently and appear to be parameter-free [14, 15]. It was
found, however, that the chiral expansion of the long- and
intermediate-range parts of the 3NF is not converged at
this order due to large fifth-order (N4 LO) corrections associated with intermediate ∆(1232) excitations [16–18].
A resolution of the long-standing discrepancies in the 3N
continuum will, therefore, likely require the knowledge of
Anisotropic flow of the fireball fed by hard partons
Martin Schulc1, ∗ and Boris Tomáˇsik2, †
1
Czech Technical University in Prague, FNSPE, CZ 11519 Prague 1, Czech Republic
2
Univerzita Mateja Bela, SK 97401 Bansk´
a Bystrica, Slovakia
and Czech Technical University in Prague, FNSPE, CZ 11519 Prague 1, Czech Republic
(Dated: September 22, 2014)
arXiv:1409.6116v1 [nucl-th] 22 Sep 2014
In nuclear collisions at highest accessible LHC energies, often more than one dijet pairs deposit
momentum into the deconfined expanding medium. With the help of 3+1 dimensional relativistic
hydrodynamic simulation we show that this leads to measurable contribution to the anisotropy of
collective transverse expansion. Hard partons generate streams in plasma which merge if they come
close to each other. This mechanism correlates the resulting contribution to flow anisotropy with
the fireball geometry and causes an increase of the elliptic flow in non-central collisions.
PACS numbers: 25.75.-q, 25.75.Ld
Keywords: heavy-ion collision, anisotropic flow, hydrodynamic simulation, jets
Study of the properties of the hottest matter ever created in laboratory is in the focus of the heavy-ion programme at the LHC. From data on jet quenching we
know that the created matter is in deconfined state. Currently, the focus is on studying the properties of such
deconfined strongly interacting matter. Comparisons of
hydrodynamic simulations with the measured data aim
at extracting the transport coefficients, mainly the viscosity.
Due to transverse expansion of the created hot matter, hadronic transverse momentum spectra show a blueshift. The blue-shift varies azimuthally. This indicates the modulation of the transverse expansion velocity as a function of the azimuthal angle. Such a modulation appears naturally in non-central collisions due
to azimuthally asymmetric shape of the initial overlap
region. However, a more detailed analysis reveals azimuthal anisotropies in every event which are causally
linked to to fluctuations in the initial state [1–6]. As these
fluctuations are propagated within the (weakly) viscous
relativistic fluid, dedicated simulation could put relevant
limits on the transport properties of the deconfined matter [2]. This is the standard approach which is being used
in present investigations: by selecting a set of initial conditions and tuning the values of viscosities one tries to
find such a setting of hydrodynamic simulations which
reproduces as many features of data as possible. The
data today are very rich with a few orders of azimuthal
anisotropies for identified species, many kinds of correlations, everything measured in various centrality classes
[7–11].
In this paper we point out another source of spectral
azimuthal anisotropy. It cannot be put into the family
of models where initial conditions are exclusively responsible for the anisotropy. At the LHC, jets are no longer
such a rare probe. They are produced in initial hard
scattering together with copious minijets and propagate
∗
†
[email protected]
[email protected]
through the deconfined medium. It is known that quarkgluon plasma quenches a large part—if not all—of the
energy and momentum of the hard partons which might
become jets. The momentum deposition from the partons into medium induces collective effects [12–21] and
owing to momentum conservation there must be net flow.
Recently in [22] the response of medium to one very energetic dijet was simulated in 3+1D hydrodynamics. In [23]
the generation of elliptic and triangular flow due to hard
partons within a 2+1D model was simulated. The introduction of jets, however, breaks longitudinal boost invariance which is implicitly assumed in a 2+1D simulation.
The influence of jets on the evolution in central collisions
was investigated in a 1+1D approach also in [24, 25].
Here we present results from our three-dimensional ideal
hydrodynamic simulation with realistic multiplicity distribution of hard partons.
In [26] it was shown with a help of a toy model that
if there are a few pairs of minijets within one event, the
wakes which they deposit may influence each other and so
lead to elliptic flow anisotropy correlated with the reaction plane. Later in [27] we have shown that the concept
of two merging wakes that follow as one stream is reproduced in ideal hydrodynamics in a static medium. Here
we apply these ideas in three-dimensional simulations of
an expanding fireball motivated by realistic collision dynamics.
We present results on first to fourth order flow
anisotropies in central and non-central collisions. Hard
partons depositing momentum themselves are capable of
generating v2 of the order 0.015 in ultra-central collisions
at the LHC. It is important that in non-central collisions
their contribution is correlated with fireball geometry.
We show that they contribute considerably to the observed anisotropy of hadronic spectra.
We perform event-by-event hydrodynamic simulations.
Our model is three-dimensional, based on ideal hydrodynamics and uses the SHASTA algorithm [28, 29] to
deal with shock fronts. For each event the initial conditions are first constructed smooth according to the optical Glauber prescription. Transverse profile of the energy
Gravity Waves generated by Sounds from Big Bang Phase Transitions
Tigran Kalaydzhyan and Edward Shuryak
arXiv:1412.5147v1 [hep-ph] 16 Dec 2014
Department of Physics and Astronomy, Stony Brook University,
Stony Brook, New York 11794-3800, USA
Inhomogeneities associated with the cosmological QCD and electroweak phase transitions produce hydrodynamical perturbations, longitudinal sounds and rotations. It has been demonstrated
numerically by Hindmarsh et al. [1] that the sounds produce gravity waves (GW), and that this
process does continue well after the phase transition is over. We further introduce a long period
of the so-called inverse acoustic cascade, between the UV momentum scale at which the sound is
originally produced and the IR scale at which GW is generated. It can be described by the Boltzmann equation, possessing stationary power and self-similar time-dependent solutions. If the sound
dispersion law allows one-to-two sound decays, the exponent of the power solution is large and a
strong amplification of the sound amplitude (limited only by the total energy) takes place. Alternative scenario dominated by sound scattering leads to smaller indices and much smaller IR sound
amplitude. We also point out that two on shell phonons can produce a gravity wave and evaluate
its rate using the so-called sound loop diagram.
I.
INTRODUCTION
Thirty years ago, in a very influential paper Witten [2]
discussed bubble dynamics, assuming that cosmic QCD
phase transition is of the first order. Among other things,
he pointed out that bubble coalescence/collisions produce inhomogeneities of the energy density, which lead
to the gravity waves (GW) production. These ideas were
soon further developed by Hogan [3] who identified relevant frequencies and provided the first estimates of the
radiation intensity.
Hogan also was the first to mention the subject of this
work – generation of the GW from the sound. Unfortunately, this idea was dormant for a very long time, being
recently revived by Hindmarsh et al. [1], who found the
hydrodynamic sound waves to be the dominant source
of the GW. This paper had triggered our interest to the
subject. Hindmarsh et al., however, were performing numerical simulations of (variant of) the electroweak (EW)
phase transition, in the traditional first order transition
setting. We will discuss connection to this work in more
detail in Section IV D.
Our paper refers to both QCD and EW transitions,
with emphasis on the former case, both because of favorable observational prospects and our background. The
main point of our paper is that, given a huge dynamical range of the problem, it is clearly impossible to cover
it in a single numerical setting. We suggest to split the
problem into distinct stages, each with its own physics,
scales and technique. We will list them starting from
the UV end of the spectrum, with momenta of the order of ambient temperature k ∼ Tc and ending at the IR
end of the spectrum, k ∼ 1/tlif e , limited by the cosmological horizon (inverse to the Universe lifetime) at the
radiation-dominated era:
(i) production of sounds from inhomogeneities,
(ii) inverse acoustic cascade, shifting the sound waves
population toward the IR,
(iii) the final conversion of sounds into GW
The stage (i) remains highly nontrivial, associated with
the dynamical details of the QCD and EW phase transition. We will not be able to provide definite predictions
on it at this point, and only make some comments on
current status of the problem in Section VI.
The stage (ii) will be our main focus. It is in fact
amenable to perturbative studies of the acoustic inverse
cascade, consisting of sound decay/scattering events.
Those are governed by the Boltzmann equation which has
been already studied in literature on acoustic turbulence
to certain extent. The stationary attractor solutions –
known as Kolmogorov-Zakharov spectra – can be identified, as well as some time-dependent self-similar solution
describing a spectrum profile moving across the dynamical range. Application of this theory allows to see how
small-amplitude sounds at the UV end of the dynamical
range are amplified and move toward smaller k.
The final step (iii) can be treated directly via a standard on-shell process for the sound + sound → GW transition, to be calculated in Section V via a sound loop
diagram.
Let us note that the studies of the QCD phase transition region, from the confined (or hadronic) phase to
the deconfined Quark-Gluon Plasma (QGP) now constitute the mainstream of the heavy-ion physics. Experiments, done mostly at the RHIC in Brookhaven and now
at CERN LHC, revealed that the matter above and near
the phase transition seems to be a nearly perfect liquid
with a small viscosity. Hydrodynamic description of the
subsequent explosion – sometimes called the Little Bang
– turns out to be very accurate.
Furthermore, initial state fluctuations create hydrodynamical perturbations of the Little Bang – the sounds.
The long-wave ones can survive till the freezeout time
without significant damping and are observed experimentally, in the correlation functions of the secondaries.
These observations are in excellent agreement with the
hydrodynamics see, e.g., [6, 7], and this ensures exis-
arXiv:1412.5117v1 [hep-ph] 16 Dec 2014
Lifting degenerate neutrino masses, threshold
corrections and maximal mixing
Wolfgang Gregor Hollik∗†
Institut für Theoretische Teilchenphysik
Karlsruhe Institute of Technology
In the scenario with degenerate neutrino masses at tree-level, we show how threshold corrections
with either non-trivial or trivial mixing at tree-level have the power to generate the observed
deviations from a degenerate spectrum. Moreover, it is possible to also generate the mixing fully
radiatively when there is trivial mixing at tree-level.
We give a brief overview over the topic and discuss the outcome of threshold corrections for
degenerate neutrino masses in a supersymmetric model. A detailed description can be found
in [1].
Flavorful Ways to New Physics – FWNP,
28-31 October 2014
Freudenstadt – Lauterbad, Germany
∗ Speaker.
† Report
number: TTP14-038
arXiv:1412.4950v1 [hep-ph] 16 Dec 2014
HEPHY-PUB 946/14
UWThPh-2014-34
December 2014
THE SPINLESS RELATIVISTIC KINK-LIKE
PROBLEM
Wolfgang LUCHA∗
Institute for High Energy Physics,
Austrian Academy of Sciences,
Nikolsdorfergasse 18, A-1050 Vienna, Austria
†
¨
Franz F. SCHOBERL
Faculty of Physics, University of Vienna,
Boltzmanngasse 5, A-1090 Vienna, Austria
Abstract
We constrain the possible bound-state solutions of the spinless Salpeter equation (the most
obvious semirelativistic generalization of the nonrelativistic Schrödinger equation) with an
interaction between the bound-state constituents given by the kink-like potential (a central
potential of hyperbolic-tangent form) by formulating a bunch of very elementary boundary
conditions to be satisfied by all solutions of the eigenvalue problem posed by a bound-state
equation of this type, only to learn that all results produced by a procedure very much liked
by some quantum-theory practitioners prove to be in severe conflict with our expectations.
Keywords: relativistic bound states, Bethe–Salpeter formalism, spinless Salpeter equation,
kink-like potential
PACS numbers: 03.65.Pm, 03.65.Ge, 12.39.Pn, 11.10.St
∗
†
E-mail address: [email protected]
E-mail address: [email protected]
Zeeman interaction and chiral symmetry breaking by tilted magnetic field in the
(2+1)-dimensional Gross–Neveu model
K.G. Klimenko
a
b
a,b
, R.N. Zhokhov
a
Institute for High Energy Physics, 142281, Protvino, Moscow Region, Russia and
University ”Dubna” (Protvino branch), 142281, Protvino, Moscow Region, Russia
arXiv:1412.4945v1 [hep-ph] 16 Dec 2014
Magnetic catalysis of the chiral symmetry breaking and other magnetic properties of the (2+1)dimensional Gross–Neveu model are studied taking into account the Zeeman interaction of spin-1/2
quasi-particles (electrons) with tilted (with respect to a system plane) external magnetic field. The
Zeeman interaction is proportional to magnetic moment µB of electrons. It is shown that at µB 6= 0
the magnetic catalysis effect is drastically changed in comparison with the µB = 0 case.
PACS numbers: 11.30.Qc,71.30.+h
I.
INTRODUCTION
It is well known that during last three decades a lot of attention is paid to the investigation of (2+1)-dimensional
quantum field theories (QFT) under influence of different external conditions. In particular, the (2+1)-dimensional
Gross-Neveu (GN) [1] type models are among the most popular [2–4]. There are several basic motivations for this
interest. Since low dimensional theories have a rather simple structure, they can be used in order to develop our
physical intuition for different physical phenomena taking place in real (3+1)-dimensional world (such as dynamical
symmetry breaking [1–5], color superconductivity [6] etc). Another example of this kind is the spontaneous chiral
symmetry breaking induced by external magnetic fields, i.e. the magnetic catalysis effect (see the recent reviews [7, 8]
and references therein). For the first time this effect was also studied in terms of (2+1)-dimensional GN models [9].
In addition, low dimensional models are useful in elaborating new QFT methods like the large-N technique [1, 3] and
the optimized expansion method [10] etc.
However, a more fundamental reason for the study of these theories is also well known. Indeed, there are a lot of
condensed matter systems which, firstly, have a (quasi-)planar structure and, secondly, their low-energy excitation
spectrum is described adequately by relativistic Dirac-like equation rather than by Schrödinger one.
II.
THE MODEL AND ITS THERMODYNAMIC POTENTIAL
We suppose that some physical system is localized in the spatially two-dimensional plane perpendicular to the zˆ
coordinate axis of usual tree-dimensional space. Moreover, there is an external homogeneous and time independent
~ tilted with respect to this plane. The corresponding (3+1)-dimensional vector potential Aµ is given
magnetic field B
by A0,1 = 0, A2 = B⊥ x, A3 = Bk y We assume that the planar physical system consists of quasi-particles (electrons)
~ Moreover, it is also supposed that their
with two spin projections, ±1/2, on the direction of magnetic field B.
low-energy dynamics is described by the following (2+1)-dimensional Gross-Neveu type Lagrangian
L=
2
X
k=1
i
h
G
ψ¯ka γ 0 i∂t + γ 1 i∇1 + γ 2 i∇2 − ν(−1)k γ 0 ψka +
N
2
X
ψ¯ka ψka
k=1
!2
,
(1)
where ∇1,2 = ∂1,2 + ieA1,2 and the summation over the repeated index a = 1, ..., N of the internal O(N ) group is
implied. For each fixed value of k = 1, 2 and a = 1, ..., N the quantity ψka (x) in (1) means the Dirac fermion field,
transforming over a reducible 4-component spinor representation. We suppose that spinor fields ψ1a (x) and ψ2a (x)
(a = 1, ..., N ) correspond to electrons with spin projections 1/2 and -1/2 on the direction of an external magnetic field,
respectively. In (1) the ν-term is introduced in order to take into account the Zeeman
q interaction energy of electrons
2 , g is the spectroscopic
~
~
~
with external magnetic field B. Hence, in our case ν = gS µB |B|/2, where |B| = Bk2 + B⊥
S
Lande factor and µB is an electron magnetic moment, i.e. the Bohr magneton.
The model (1) is invariant under the discrete chiral transformation, ψka → γ 5 ψka . Certainly, there is the O(N )
invariance of the Lagrangian (1). Finally note that at N = 1 the quasi-particle spectrum of the model (1) is just the
same as in the monolayer graphene [19], but at N > 1 one can interpret our results as occurring in the N -layered
system.
In the following we use an auxiliary theory with the Lagrangian density
2
L=−
N σ2 X ¯ 0
+
ψka γ i∂t + γ 1 i∇1 + γ 2 i∇2 + µk γ 0 − σ ψka ,
4G
k=1
(2)
Estimating matter induced CPT violation in Long-Baseline Neutrino Experiments
Monika Randhawa∗
University Institute of Engineering and Technology, Panjab University, Chandigarh, India
Mandip Singh and Manmohan Gupta
Department of Physics, Centre of Advanced Study, Panjab University, Chandigarh, India.
arXiv:1412.4903v1 [hep-ph] 16 Dec 2014
We examine matter induced CPT violation effects in long baseline electron neutrino appearance
experiments in a low energy neutrino factory setup. Assuming CPT invariance in vacuum, the
magnitude of CPT violating asymmetry in matter has been estimated using the exact expressions
for the transition probabilities. The dependence of the asymmetry on the oscillation parameters
like mixing angles, mass squared differences as well as on the Dirac CP violating phase has been
investigated.
I.
INTRODUCTION
In particle theory, the discrete symmetries C, P and T
have a central importance. Although C, P, CP and T are
violated [1], CPT is a good symmetry [2] in the Standard
Model, therefore, the fundamental CPT violation may be
connected to physics beyond the SM, such as string theory [3, 4]. Experimentally, CPT non-conservation can be
probed in the neutrino oscillations, where it would manifest itself by showing different oscillation probabilities for
the transitions να → νβ and ν¯β → ν¯α [5, 6]. In this context, although a 2010 observation of MINOS [7] reported
tension between νµ and ν¯µ oscillation parameters, suggesting CPT violation, the difference was not observed
in their revised results in 2012 [8]. Nevertheless, the interest in the search of CPT violation continues [9], particularly owing to the increasing precision with which the
oscillation parameters are being measured in the current
generation of long baseline experiments [10–13].
Even if it is assumed that the CPT invariance theorem holds good, when neutrinos propagate in a material
medium, the matter effects, arising due to interaction of
neutrinos with an asymmetric matter, lead to CPT violation in neutrino oscillations, known as extrinsic or fake
CPT violation [14, 15]. The matter effects become all
the more important in the long baseline neutrino oscillation experiments, where neutrinos travel a long distance
in the earth’s matter [10–13]. These fake effects should
be accounted for, while searching for CPT violation.
The matter induced CPT violation has been estimated
in some of the papers in the atmospheric as well as long
baseline experiments, primarily by using the approximate
analytic expressions for the probabilities for various neutrino oscillation channels [15]. The validity of the various
approximations depends on the baseline length and the
energy of the neutrino, as well as on the mixing angle
θ13 . Therefore, keeping in mind the recently determined
large value of θ13 [16], to which the appearance probabilities are very sensitive, as well as the increased precision
∗
[email protected]
in the measurement of other oscillation parameters, it
becomes imperative to calculate the probabilities in an
exact manner and to update the estimates of CPT asymmetry in neutrino oscillation experiments. This becomes
particularly important in view of the large L and E range
available to the neutrino in the ongoing and future experiments. In this regard, the channel that has been most
extensively used to estimate the magnitude of CPT violating parameters is the disappearance channel νµ → νµ
[14, 15] as it offers high event rates and little beam contamination. Further, the neutrino oscillation effects in
this channel are large, however, it has been pointed out
that the matter effects are rather small in νµ → νµ oscillations [14]. Therefore, to study the effects of matter
potential, leading to extrinsic CPT violation, the subdominant channel νµ → νe looks to be more promising.
Further, this channel is the principle appearance channel
available to conventional beams and Superbeams. However, the corresponding CPT conjugate channel ν¯e → ν¯µ
is not going to be explored in the ongoing and forthcoming experiments [10–13] , as these explore channels which
are CP conjugate of each other. In this regard neutrino
factories, which are under active consideration [17] offer
a combination of CP and CPT conjugate channels, as
both electron as well as muon neutrinos are present in
the beam. The challenging task in a neutrino factory is
to measure the sign of the charge of the produced lepton.
The sign of a muon charge can be determined using a
magnetized iron neutrino detector (MIND) [18]. The possibility to measure the electron (or positron) charge with
magnetized liquid argon detector has also been explored
[19]. Neutrino factories with their high luminosities and
low backgrounds allow to investigate the phenomenon of
neutrino oscillations with unprecedented accuracy.
Assuming CPT invariance in vacuum, the purpose of
this paper is to investigate the matter induced CPT violation effects in the νµ → νe transitions in four different scenarios of long baseline neutrino oscillation experiments: e.g. S1: L = 300 Km and E = 1 GeV, S2:
L = 1300 Km and E = 3.5 GeV, S3: L = 2300 Km and
E = 5 GeV, S4: L = 3000 Km and E = 7 GeV, where
L is the baseline length and E is the average neutrino
energy. The choice of baseline and neutrino energy for
keV Sterile Neutrino Dark Matter and Low Scale Leptogenesis
Sin Kyu Kang∗ and Ayon Patra†
Institute for Convergence Fundamental Study,
Seoul National University of Science and Technology, Seoul 139-743, Korea
arXiv:1412.4899v1 [hep-ph] 16 Dec 2014
Abstract
We consider a simple extension of the Standard Model to consistently explain the observation
of a peak in the galactic X-ray spectrum at 3.55 keV and the light neutrino masses along with the
baryon asymmetry of the universe. The baryon asymmetry is generated through leptogenesis,
the lepton asymmetry being generated by the decay of a heavy neutrino with TeV mass scale.
The extra singlet fermion introduced in the model can be identified as a warm dark matter
candidate of mass 7.1 keV. It decays with a lifetime much larger than the age of the universe,
producing a final state photon. The Yukawa interactions between the extra singlet neutrino
and a heavier right-handed neutrino play a crucial role in simultaneously achieving low scale
leptogenesis and relic density of the keV dark matter candidate.
PACS numbers: 98.80.-k, 95.35.+d, 14.60.St, 14.60.Pq
∗
†
The right generations
Alfredo Aranda,a,b∗ Jose A. R. Cembranos,a,b,c
†
(a)
arXiv:1412.4836v1 [hep-ph] 15 Dec 2014
(c)
Facultad de Ciencias, CUICBAS, Universidad de Colima, 28040 Colima, Mexico;
(b)
Dual C-P Institute of High Energy Physics, 28040 Colima, Mexico; and
Departamento de F´ısica Te´
orica I, Universidad Complutense de Madrid, E-28040 Madrid, Spain.
The Standard Model has three generations of fermions and although it does not contain any
explicit reason for this, the existence of additional generations is now very constrained by experiment.
Present measurements are saturating perturbative unitarity limits. The main idea of this work is to
show that those restrictions can be relaxed if the new generations experience different interactions.
This new setup leads to the presence of additional stable degrees of freedom that give rise to a very
rich phenomenology for cosmology, astrophysics and particle physics. The stability is a consequence
of the conservation of new accidental baryon and lepton numbers. We present an explicit example
by introducing a fourth generation charged under a new SU (2)R gauge interaction instead of the
standard SU (2)L . The simplest implementations lead to models that contain stable quarks, leptons
and neutrinos. We show that these new particles can have a wide range of masses within a nonstandard cosmological set-up. Indeed, the new neutrinos (and neutral leptons) constitute viable
dark matter candidates if they are the lightest of these new particles.
There have been several motivations to explore the
possibility of a fourth (or more) generation(s). This has
typically been done by postulating an exact (heavier)
set of quarks and leptons in complete analogy with the
known three generations, namely with the same chiral
charges under the Standard Model (SM) gauge group.
Immediate challenges to this proposal are the required
heaviness of the fourth neutrino, as required by the Zwidth, and more recently and devastating, due to the
value obtained for the Higgs mass [1, 2], the difficulty
in providing a large enough mass to the new quarks
(basically one would need non-perturbative Yukawa couplings) [3–5]. Thus, it seems that introducing a new generation has fallen out of grace.
There are also several reasons to extend the gauge
structure of the SM, most of which emane from the idea
of gauge coupling unification and grand unified theories
(GUTs). In this regard, a particularly attractive and
useful scenario is that of the so-called left-right models
where an SU (2)R is added to the SM gauge group [6–8].
The basic idea is that what we observe as right handed
fermions, singlets under the SM SU (2)L , are really remnants of fermionic SU (2)R doublets. It just so happens
that this new symmetry was broken by the vacuum expectation value (vev) of a bi-doublet in such a way that
only the SM gauge group survives and its matter content remains massless, including now an SU (2)L doublet
scalar. This general picture is not only nice in terms of
restoring the left-right symmetry lost in the SM, but is
also easily embedded in larger grand unified models with
a single big gauge group.
In this short letter we forget about all of that and
present a couple of simple models where a new right generation is included and the SM gauge group is extended
with an extra SU (2)R but with no regard, nor worry,
about its possible implementation into a GUT. The idea
is to consider the following gauge group: SU (3)C ×
SU (2)L × SU (2)R × U (1)X , where X may or not denote Hypercharge (Y) 1 . Let’s first suppose it does not.
We want to generate the following symmetry breaking
hHR i
pattern: SU (3)C × SU (2)L × SU (2)R × U (1)X −→
hHL i
SU (3)C × SU (2)L × U (1)Y −→ SU (3)C × U (1)em .
We can accomplish it by introducing two scalar fields
HR ∼ (1, 1, 2, 1/2) and HL ∼ (1, 2, 1, 1/2), where the
numbers in parenthesis correspond to their charges under
SU (3)C × SU (2)L × SU (2)R × U (1)X . The idea is that
the vev of HR gives the first breaking and that of HL
the second. Note that the electric charge is given by
Q = τ3L + Y = τ3L + τ3R + X. The broken gauge boson
spectrum consists of six massive gauge bosons denoted
by WR± , ZR and the usual W ± and Z 0 ≡ Z. The mass
scale of the right-gauge bosons is that of hHR i.
As for matter fields, the content is that of the SM (all
SM fields being singlets under SU (2)R ) and a new (or
more) right generation(s) (fully singlet under SU (2)L )
charged, in a mirror way, under SU (2)R . Namely for
leptons we have
Li ∼ (1, 2, 1, −1/2) , R′ ∼ (1, 1, 2, −1/2) ,
ERi ∼ (1, 1, 1, −1) , EL′ ∼ (1, 1, 1, −1) ,
1
∗ Electronic
† Electronic address: [email protected]
(1)
In this setup we do not explore the possibility of gauged Baryon
(B) and/or Lepton (L) numbers (nor B-L), and they are just
accidental global symmetries of the Lagrangian.
BRST Cohomology and Physical Space of the GZ Model
Martin Schaden∗
Department of Physics, Rutgers, The State University of New Jersey,
101 Warren Street, Newark, New Jersey - 07102, USA
arXiv:1412.4823v1 [hep-ph] 15 Dec 2014
Daniel Zwanziger†
Physics Department, New York University,
4 Washington Place, New York, NY 10003, USA
Abstract: We address the issue of BRST symmetry breaking in the GZ model,
a local, renormalizable, non-perturbative approach to QCD. Explicit calculation of
several examples reveals that BRST symmetry breaking apparently afflicts the unphysical sector of the theory, but may be unbroken where needed, in cases of physical
interest. Specifically, the BRST-exact part of the conserved energy-momentum tensor and the BRST-exact term in the Kugo-Ojima confinement condition both have
vanishing expectation value. We analyze the origin of the breaking of BRST symmetry in the GZ model, and obtain a useful sufficient condition that determines which
operators preserve BRST. Observables of the GZ theory are required to be invariant
under a certain group of symmetries that includes not only BRST but also others.
The definition of observables is thereby sharpened, and excludes all operators known
to us that break BRST invariance. We take as a hypothesis that BRST symmetry
is unbroken by this class of observables. If the hypothesis holds, BRST breaking
is relegated to the unphysical sector of the GZ theory, and its physical states are
obtained by the usual cohomological BRST construction. The fact that the horizon
condition and the Kugo-Ojima confinement criterion coincide assures that color is
confined in the GZ theory.
PACS numbers: 11.15.-q,11.15.Tk
∗
[email protected]
†
[email protected]
Prepared for submission to JCAP
arXiv:1412.4821v1 [hep-ph] 15 Dec 2014
Dark Matter with Topological
Defects in the Inert Doublet Model
Mark Hindmarsh,1,2 Russell Kirk,3 Jose Miguel No,1 and
Stephen M. West3
1 Dept.
of Physics and Astronomy, University of Sussex, Brighton BN1 9QH, U.K.
of Physics and Helsinki Institute of Physics, P.O. Box 64, 00014 Helsinki
University, Finland
3 Dept. of Physics, Royal Holloway University of London, Egham, Surrey TW20 0EX,
U.K.
[email protected], [email protected]
2 Department
Abstract. We examine the production of dark matter by decaying topological defects in
the high mass region mDM mW of the Inert Doublet Model, extended with an extra
U(1) gauge symmetry. The density of dark matter states (the neutral Higgs states of
the inert doublet) is determined by the interplay of the freeze-out mechanism and the
additional production of dark matter states from the decays of topological defects, in
this case cosmic strings. These decays increase the predicted relic abundance compared
to the standard freeze-out only case, and as a consequence the viable parameter space
of the Inert Doublet Model can be widened substantially. In particular, for a given dark
matter annihilation rate lower dark matter masses become viable. We investigate the
allowed mass range taking into account constraints on the energy injection rate from
the diffuse γ-ray background and Big Bang Nucleosynthesis, together with constraints
on the dark matter properties coming from direct and indirect detection limits. For
the Inert Doublet Model high-mass region, an inert Higgs mass as low as ∼ 200 GeV
is permitted. There is also an upper limit on string mass per unit length, and hence
the symmetry breaking scale, from the relic abundance in this scenario. Depending on
assumptions made about the string decays, the limits are in the range 1012 GeV to 1013
GeV.
MCTP-14-44
Neutrino Masses and Sterile Neutrino Dark Matter from the PeV Scale
Samuel B. Roland, Bibhushan Shakya, and James D. Wells
arXiv:1412.4791v1 [hep-ph] 15 Dec 2014
1
Michigan Center for Theoretical Physics, University of Michigan, Ann Arbor MI 48109, USA
The Higgs boson mass of 125 GeV is suggestive of superpartners at the PeV scale. We show
that new physics at this scale can also produce active neutrino masses via a modified, low energy
seesaw mechanism and provide a sterile neutrino dark matter candidate with keV-GeV scale mass.
These emerge in a straightforward manner if the right-handed neutrinos are charged under a new
symmetry broken by a scalar field vacuum expectation value at the PeV scale. The dark matter
relic abundance can be obtained through active-sterile oscillation, freeze-in through the decay of
the heavy scalar, or freeze-in via non-renormalizable interactions at high temperatures. The theory
also contains two heavier sterile neutrinos, which can decay before BBN and remain consistent with
cosmological observations. The low energy effective theory maps onto the widely studied νMSM
framework.
MOTIVATION
A natural resolution of the hierarchy problem has long
pointed to the weak scale as the natural scale for supersymmetry. Weak scale supersymmetry was additionally
motivated by the WIMP miracle, which offered a natural
explanation of dark matter and its observed abundance.
However, the predictions of the most natural setups – a
light Higgs boson, weak scale superpartners (in particular stops and gluinos) within reach of the first run of the
LHC, and detection of dark matter at direct detection
experiments – have all failed to materialize, suggesting
that the electroweak scale may be fine-tuned after all,
and the scale of new physics may lie elsewhere.
Independent of such preconceived notions of naturalness, the measured mass of the Higgs boson at 125 GeV
now provides a direct probe of where this scale might lie.
The Higgs mass at one loop with no sfermion mixing in
the MSSM is
m2h ≈ m2Z cos2 2β +
3m4t
ln(m2t˜ /m2t ).
4π 2 v 2
(1)
For tanβ ≈ O(1), the observed Higgs mass is obtained for
sfermion masses at 1 − 100 PeV [1–3]. Even prior to the
Higgs mass measurement, there were strong arguments
for supersymmetry at such high scales from flavor, CP,
and unification considerations [4–7].
This paper examines whether the neutrino sector and
a dark matter candidate can also emerge naturally from
the PeV scale. Since neutrino masses require physics beyond the Standard Model, a common origin of the Higgs
mass, dark matter, and neutrino masses is an extremely
attractive prospect.
The traditional explanation of neutrino masses is a seesaw mechanism, involving right-handed, Standard Model
(SM)-singlet sterile neutrinos Ni that enable the following terms in the Lagrangian
¯ α H † Ni + M i N
¯ c Ni .
L ⊃ yαi L
u
i
(2)
The first term leads to a Dirac mass between the left and
right handed neutrinos once Hu obtains a vacuum expectation value (vev), and the second term is a Majorana
mass for the sterile neutrinos. If M yhHu i, the seesaw
mechanism gives active neutrino masses at (yhHu i)2 /M .
GUT scale seesaw models [8–12] employ y ∼ O(1) and
M ∼ 1010 − 1015 GeV, which can explain the small active neutrino masses but does not shed any light on dark
matter. The low energy counterpart, with all masses below the electroweak scale, has been extensively studied
in the effective framework of the Neutrino Minimal Standard Model (νMSM) [13–15], which carries the additional
attractive feature of a keV scale sterile neutrino that is a
viable warm or cold dark matter candidate. A successful
realization of active neutrino masses in the νMSM, however, requires y 2 . 10−13 . The purpose of this paper is
to explore a modified setup where both active neutrino
masses and a dark matter candidate can be realized with
predominantly O(1) couplings and the PeV scale, which
is motivated by the Higgs mass measurement as the scale
of new physics.
Finally, while not the main motivation of this paper,
some recent observational hints add further relevance to
this study. A 7 keV sterile neutrino dark matter candidate can explain the recent observation of a monochromatic line signal at 3.5 keV in the X-ray spectrum of
galactic clusters [16]. The observation of neutrinos with
PeV scale energies at IceCube [14, 17] also hint at a possible connection between the neutrino sector and physics
at the PeV scale. These can be accommodated in our
framework, but are not necessary ingredients, hence we
leave this task to a later work.
THE MODEL
As in the νMSM, the neutrino sector is extended by
three SM-singlet, sterile neutrinos Ni . While the Ni are
uncharged under the SM gauge group, it is unlikely that
NUHEP-TH/14-09
Heavy Neutrinos and the Kinematics of Tau Decays
Andrew Kobach and Sean Dobbs
arXiv:1412.4785v1 [hep-ph] 15 Dec 2014
Northwestern University, Department of Physics & Astronomy,
2145 Sheridan Road, Evanston, IL 60208, USA
Searches for heavy neutrinos often rely on the possibility that the heavy neutrinos will decay
to detectable particles. Interpreting the results of such searches requires a particular model for
the heavy-neutrino decay. We present a method for placing limits on the probability that a tau
can couple to a heavy neutrino, |Uτ 4 |2 , using only the kinematics of semi-leptonic tau decays,
instead of a specific model. Our study suggests that B factories with large datasets, such a
Belle and BaBar, may be able to place stringent limits on |Uτ 4 |2 as low as O(10−7 − 10−3 )
when 100 MeV . m4 . 1.2 GeV, utilizing minimal assumptions regarding the decay modes
of heavy neutrinos.
PACS numbers: 13.35.Dx, 14.60.St
I.
INTRODUCTION
The explanation of neutrino masses requires degrees of freedom beyond those currently available
in the standard model (SM). A popular option is to augment the SM with new “neutrinos” whose
masses can, in principle, exist anywhere between the eV and GUT scales. This generic possibility
offers the potential to address a broad range of open puzzles in particle physics, well beyond neutrino
masses (for an extensive review, see Ref. [1] and references found therein).
In this work, we consider that heavy neutrinos can interact with the tau via charged-current
weak interactions. For simplicity, we take there to be only one such heavy neutrino, ν4 . Here, we
let the probability that the tau interacts with ν4 to be |Uτ 4 |2 , and the probability that the tau
interacts with the known “light” neutrinos (ν1 , ν2 , ν3 ) to be 1 − |Uτ 4 |2 .
Here, we summarize the relatively few sources of constraints on the value of |Uτ 4 |2 , all of which
assume ν4 can interact with SM particles via the weak interactions. Limits are estimated by
NOMAD [2] and CHARM [3] experiments, which have detectors located downstream from a beam
of high-energy protons incident on a fixed target. Under the assumption that ν4 can decay primarily
via neutral-current weak interactions, these two experiments search for the signatures associated
with ν4 decay within the detectors’ fiducial region. The DELPHI experiment [4] at LEP estimates
limits on the value of |Uτ 4 |2 by searching for signatures of a (mostly) sterile ν4 that decays to
“visible” SM particles in e+ e− → Z → νν4 events. Lastly, the authors of Ref. [5] use measurements
of tau and meson branching ratios to estimate limits on |Uτ 4 |2 , assuming that the mass and lifetime
of the tau are known to infinite precision. All of the aforementioned constraints can be seen in
Fig. 2. Taken together, these studies estimate that the value of |Uτ 4 |2 < O(10−5 − 10−3 ) for 50
MeV . m4 . 60 GeV, where m4 is the mass of ν4 .
These analyses all utilize assumptions regarding the possible branching ratios of ν4 . It is possible,
however, that one can search for the presence of a heavy neutrino without relying on a specific model
that dictates its lifetime and decay modes. If the tau decays semi-leptonically into a neutrino and
a hadronic system, τ − → ν + h− (ν is a mass eigenstate), then the possible energy and momentum
of h− , i.e., its kinematic phase space, itself can contain information whether it “recoiled” against a
heavy neutrino.1 The kinematic phase space of h− could be the superposition of two possibilities: the
1
Similar in spirit are analyses that place limits on the “mass of tau neutrino,” e.g., ALEPH [6] and CLEO [7]. The
CP3-Origins-2014-044 DNRF90
DIAS-2014-44
RM3-TH/14-18
arXiv:1412.4776v1 [hep-ph] 15 Dec 2014
Leptogenesis in SO(10)
Chee Sheng Fonga , Davide Melonib , Aurora Meronic , Enrico Nardid
a
Instituto de F´ısica, Universidade de S˜
ao Paulo,
C. P. 66.318, 05315-970 S˜
ao Paulo, Brazil.
b
Dipartimento di Matematica e Fisica,
Via della Vasca Navale 84, 00146 Roma.
c
CP 3 -Origins & the Danish Institute for Advanced Study Danish IAS,
Univ. of Southern Denmark, Campusvej 55, DK-5230 Odense.
d
INFN, Laboratori Nazionali di Frascati,
C.P. 13, 100044 Frascati, Italy.
[email protected], [email protected]
Abstract: We consider SO(10) Grand Unified Theories (GUTs) with vacuum expectation
values (vevs) for fermion masses in the 10 + 126 representation. We show that the baryon
asymmetry generated via leptogenesis is completely determined in terms of measured low
energy observables and of one single high energy parameter related to the ratio of the 10
and 126 SU (2) doublet vevs. We identify new decay channels for the heavy Majorana
neutrinos into SU (2) singlet leptons ec which can sizeably affect the size of the resulting
baryon asymmetry. We describe how to equip SO(10) fits to low energy data with the
additional constraint of successful leptogenesis, and we apply this procedure to the fits
carried out in ref. [1]. We show that a baryon asymmetry in perfect agreement with
observations is obtained.
Keywords: Leptogenesis, Grand Unification, Neutrino Physics
UCLA/14/TEP/108
SB/F/442-14
SLAC–PUB–16144
Saclay–IPhT–T14/185
IPPP/11/82
FR-PHENO-2014-002
Extrapolating W -Associated Jet-Production Ratios at the LHC
arXiv:1412.4775v1 [hep-ph] 15 Dec 2014
Z. Berna , L. J. Dixonb , F. Febres Corderoc,d ,
S. Höcheb , D. A. Kosowere , H. Itad and D. Maˆıtref
a
b
c
Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547, USA
SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94309, USA
Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, D–79104 Freiburg, Germany
d
e
Departamento de F´ısica, Universidad Simón Bol´ıvar, Caracas 1080A, Venezuela
Institut de Physique Théorique, CEA–Saclay, F–91191 Gif-sur-Yvette cedex, France
f
Department of Physics, University of Durham, Durham DH1 3LE, UK
Abstract
Electroweak vector-boson production, accompanied by multiple jets, is an important background
to searches for physics beyond the Standard Model. A precise and quantitative understanding of
this process is helpful in constraining deviations from known physics. We study four key ratios in
W + n-jet production at the LHC. We compute the ratio of cross sections for W + n- to W+ (n−1)jet production as a function of the minimum jet transverse momentum. We also study the ratio
differentially, as a function of the W -boson transverse momentum; as a function of the scalar sum
of the jet transverse energy, HTjets ; and as a function of certain jet transverse momenta. We show
how to use such ratios to extrapolate differential cross sections to W + 6-jet production at nextto-leading order, and we cross-check the method against a direct calculation at leading order. We
predict the differential distribution in HTjets for W + 6 jets at next-to-leading order using such an
extrapolation. We use the BlackHat software library together with SHERPA to perform the
computations.
PACS numbers: 12.38.-t, 12.38.Bx, 13.87.-a, 14.70.Hp
1
Thermodynamics of pairing transition in hot nuclei
Lang Liu (刘朗)
School of Science, Jiangnan University, Wuxi 214122, China.
State Key Laboratory of Nuclear Physics and Technology,
School of Physics, Peking University, Beijing 100871, China
Zhen-Hua Zhang (张振华)
School of Physics, Peking University, Beijing 100871, China.
Mathematics and Physics Department,
North China Electric Power University, Beijing 102206, China
Peng-Wei ZHao (赵鹏巍)∗
Yukawa Institute for Theoretical Physics,
Kyoto University, Kyoto 606-8502, Japan.
School of Physics, Peking University, Beijing 100871, China
Abstract
The pairing correlations in hot nuclei
162 Dy
are investigated in terms of the thermodynamical
properties by covariant density functional theory. The heat capacities CV are evaluated in the
canonical ensemble theory and the paring correlations are treated by a shell-model-like approach,
in which the particle number is conserved exactly. A S-shaped heat capacity curve, which agrees
qualitatively with the experimental data, has been obtained and analyzed in details. It is found
that the one-pair-broken states play crucial roles in the appearance of the S shape of the heat
capacity curve. Moreover, due to the effect of the particle-number conservation, the pairing gap
varies smoothly with the temperature, which indicates a gradual transition from the superfluid to
the normal state.
∗
[email protected]
1
arXiv:1412.5140v1 [nucl-ex] 16 Dec 2014
Separated Response Functions in
Exclusive, Forward π ± Electroproduction on Deuterium
G.M. Huber,1 H.P. Blok,2, 3 C. Butuceanu,1 D. Gaskell,4 T. Horn,5 D.J. Mack,4 D. Abbott,4 K. Aniol,6 H. Anklin,7, 4
C. Armstrong,8 J. Arrington,9 K. Assamagan,10 S. Avery,10 O.K. Baker,10, 4 B. Barrett,11 E.J. Beise,12 C. Bochna,13
W. Boeglin,7 E.J. Brash,1 H. Breuer,12 C.C. Chang,12 N. Chant,12 M.E. Christy,10 J. Dunne,4 T. Eden,4, 14 R. Ent,4
H. Fenker,4 E.F. Gibson,15 R. Gilman,16, 4 K. Gustafsson,12 W. Hinton,10 R.J. Holt,9 H. Jackson,9 S. Jin,17
M.K. Jones,8 C.E. Keppel,10, 4 P.H. Kim,17 W. Kim,17 P.M. King,12 A. Klein,18 D. Koltenuk,19 V. Kovaltchouk,1
M. Liang,4 J. Liu,12 G.J. Lolos,1 A. Lung,4 D.J. Margaziotis,6 P. Markowitz,7 A. Matsumura,20 D. McKee,21
D. Meekins,4 J. Mitchell,4 T. Miyoshi,20 H. Mkrtchyan,22 B. Mueller,9 G. Niculescu,23 I. Niculescu,23 Y. Okayasu,20
L. Pentchev,8 C. Perdrisat,8 D. Pitz,24 D. Potterveld,9 V. Punjabi,14 L.M. Qin,18 P.E. Reimer,9 J. Reinhold,7
J. Roche,4 P.G. Roos,12 A. Sarty,11 I.K. Shin,17 G.R. Smith,4 S. Stepanyan,22 L.G. Tang,10, 4 V. Tadevosyan,22
V. Tvaskis,2, 3 R.L.J. van der Meer,1 K. Vansyoc,18 D. Van Westrum,25 S. Vidakovic,1 J. Volmer,2, 26
W. Vulcan,4 G. Warren,4 S.A. Wood,4 C. Xu,1 C. Yan,4 W.-X. Zhao,27 X. Zheng,9 and B. Zihlmann4, 28
(The Jefferson Lab Fπ Collaboration)
1
University of Regina, Regina, Saskatchewan S4S 0A2, Canada
2
VU university, NL-1081 HV Amsterdam, The Netherlands
3
NIKHEF, Postbus 41882, NL-1009 DB Amsterdam, The Netherlands
4
Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606
5
Catholic University of America, Washington, DC 20064
6
California State University Los Angeles, Los Angeles, California 90032
7
Florida International University, Miami, Florida 33119
8
College of William and Mary, Williamsburg, Virginia 23187
9
Physics Division, Argonne National Laboratory, Argonne, Illinois 60439
10
Hampton University, Hampton, Virginia 23668
11
Saint Mary’s University, Halifax, Nova Scotia B3H 3C3 Canada
12
University of Maryland, College Park, Maryland 20742
13
University of Illinois, Champaign, Illinois 61801
14
Norfolk State University, Norfolk, Virginia 23504
15
California State University, Sacramento, California 95819
16
Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854
17
Kyungpook National University, Daegu, 702-701, Republic of Korea
18
Old Dominion University, Norfolk, Virginia 23529
19
University of Pennsylvania, Philadelphia, Pennsylvania 19104
20
Tohoku University, Sendai, Japan
21
New Mexico State University, Las Cruces, New Mexico 88003-8001
22
A.I. Alikhanyan National Science Laboratory, Yerevan 0036, Armenia
23
James Madison University, Harrisonburg, Virginia 22807
24
DAPNIA/SPhN, CEA/Saclay, F-91191 Gif-sur-Yvette, France
25
University of Colorado, Boulder, Colorado 80309
26
DESY, Hamburg, Germany
27
Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
28
University of Virginia, Charlottesville, Virginia 22901
Background: Measurements of forward exclusive meson production at different squared four-momenta of the
exchanged virtual photon, Q2 , and at different four-momentum transfer, t, can be used to probe QCD’s transition
from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales.
Ratios of separated response functions in π − and π + electroproduction are particularly informative. The ratio for
transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons
provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form
factor from electroproduction data.
Purpose: Perform the first complete separation of the four unpolarized electromagnetic structure functions
L/T /LT /T T in forward, exclusive π ± electroproduction on deuterium above the dominant resonances.
Method: Data were acquired with 2.6-5.2 GeV electron beams and the HMS+SOS spectrometers in Jefferson
Lab Hall C, at central Q2 values of 0.6, 1.0, 1.6 GeV2 at W =1.95 GeV, and Q2 = 2.45 GeV2 at W =2.22 GeV.
There was significant coverage in φ and ǫ, which allowed separation of σL,T,LT,T T .

Structural( biology( at( the( single( particle( level:( imaging( tobacco

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