1. science
2. physics

Streamlined Inexpensive Integration of a Growth Facility and
Scanning Tunneling Microscope for in situ Characterization
P. Xu, D. Qi, S.D. Barber, C.T. Cook, M.L. Ackerman, and P.M. Thibadoa)
Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701
Abstract
The integration of a scanning tunneling microscope chamber with a sample growth
facility using non-custom, commercially available parts is described. The facility also features a
newly-designed magnetic wobble stick to increase the reliability of sample transfer in a costeffective manner.
The limitations of silicon-based technology have become increasingly evident, leading
research efforts to focus on more promising materials, such as graphene. In contrast to silicon,
graphene’s most important properties reside on its surface, rather than on the characteristics of its
bulk. Surface techniques, such as scanning tunneling microscopy (STM), are therefore required
to manufacture and study graphene.
Graphene is manufactured using a variety of methods, such as mechanical exfoliation of
graphite, thermal reduction of silicon carbide, and precipitation of carbon dissolved in transition
metals.1 Most recently, the production method of choice has been epitaxial growth of graphene
a)
Electronic mail: [email protected]
-1-
arXiv:1502.03800v1 [physics.ins-det] 12 Feb 2015
Measurement of the quenching and channeling effects
in a CsI crystal used for a WIMP search
J. H. Leea,b,∗, G. B. Kima , I. S. Seonga , B. H. Kima , J. H. Kima , J. Lia , J.
W. Parka , J. K. Leea , K. W. Kima , H. Bhanga , S. C. Kima , Seonho Choia,∗∗,
J. H. Choia , H. W. Jooa , S. J. Leea , S. L. Olsena , S. S. Myunga , S. K. Kima ,
Y. D. Kimc,d , W. G. Kangd , J. H. Soe , H. J. Kime , H. S. Leef , I. S. Hahnf ,
D. S. Leonardg , J. Lih , Y. J. Lih , Q. Yueh , X. R. Lii
a
Seoul National University, Seoul 151 - 747, Korea
Korea Research Institute of Standards and Science, Daejeon 305-340, Korea
c
Center for Underground Physics, Institute for Basic Science, Daejeon 305-811, Korea
d
Sejong University, Seoul 143 - 747, Korea
e
Kyungpook National University, Daegu 702 - 701, Korea
f
Ewha womans University, Seoul 120 - 750, Korea
g
University of Seoul, Seoul 130 - 743, Korea
h
Tsinghua University, Beijing 10084, China
i
Institute of High Energy Physics (IHEP), Beijing 100049, China
b
Abstract
We have studied channeling effects in a Cesium Iodide (CsI) crystal that is
similar in composition to the ones being used in a search for Weakly Interacting Massive Particles (WIMPs) dark matter candidates, and measured its
energy-dependent quenching factor, the relative scintillation yield for electron and nuclear recoils. The experimental results are reproduced with a
GEANT4 simulation that includes a model of the scintillation efficiency as
a function of electronic stopping power. We present the measured and simulated quenching factors and the estimated effects of channeling.
∗
∗∗
[email protected]
[email protected]
Preprint submitted to Elsevier
February 13, 2015
Low-energy antiproton physics and the FLAIR facility
E. Widmann∗
Stefan Meyer Institut für subatomare Physik, Austrian Academy of Sciences,
Boltzmanngasse 3, A-1090 Vienna, Austria
arXiv:1502.03687v1 [physics.ins-det] 12 Feb 2015
February 13, 2015
Abstract
FLAIR, the Facility for Low-energy Antiproton and Ion Research has been proposed in 2004
as an extension of the planned FAIR facility at Darmstadt, Germany. FLAIR was not included
into the Modularized Start Version of FAIR, but the recent installation of the CRYRING storage
ring at GSI Darmstadt has opened new perspectives for physics with low-energy antiprotons at
FAIR.
Keywords: low-energy antiproton physics, FAIR - Facility for Antiproton and Ion Research,
FLAIR - Facility for Low-energy Antiproton and Ion Research
1
Introduction
Physics with low-energy antiprotons is currently ongoing at the Antiproton Decelerator of CERN
[1, 2], which started operation in the year 2000. In 2004, the low-energy antiproton community
launched a new initiative for a next-generation facility called Facility for Low-energy Antiproton
and Ion Research FLAIR [3, 4] at the FAIR facility that was planned to be built in Darmstadt. At
that time the long-term future of CERN-AD and thus of the field of low-energy antiproton physics
was uncertain, and FAIR was the only other facility planned where high-intensity cooled antiproton
beams would be available. The LOI of FLAIR was approved and a Baseline Technical Report [5]
was submitted and approved 2005. Thus FLAIR was included in the full FAIR facility [6] in 2009.
In the following it turned out that it was much more difficult and time consuming to establish
the international FAIR facility, and for the formal foundation of FAIR in 2010 the original program
had to be reduced to what is called the Modularized Start Version MSV. FLAIR is not part of the
MSV and was deferred to a later phase of FAIR. In the mean time, however, the successes of the
physics program at the AD had convinced CERN to extend the antiproton program and a further
acceleration ring called ELENA [7] which closely resembles the LSR ring of FLAIR was approved
in 2011. It is currently under construction and will go into operation in 2017.
In spite of not being included in the MSV, a development started by the FLAIR collaboration led
to the transfer of the CRYRING storage ring from Stockholm University to GSI in 2012. CRYRING,
which was chosen by FLAIR to be used as its central storage ring LSR, is now installed at GSI
behind the existing ESR storage ring and is being commissioned to use highly charged ions from
ESR as well as from an ion source. If a way can be found to bring antiprotons from the production
target to CRYRING, physics with low-energy antiprotons can start there, Since CRYRING was
designed to provide continuous beams that are not available at CERN, nuclear and particle physics
type experiments could be uniquely performed there.
∗
email: [email protected]
1
MPPC versus MRS APD in two-phase Cryogenic
Avalanche Detectors
A. Bondar,a,b A. Buzulutskov,a,b A. Dolgov,b E. Shemyakina,a,b, * A. Sokolov,a,b
a
Budker Institute of Nuclear Physics SB RAS, Lavrentiev avenue 11, 630090 Novosibirsk, Russia
Novosibirsk State University, Pirogov street 2, 630090 Novosibirsk, Russia
b
E-mail: [email protected]
ABSTRACT: Two-phase Cryogenic Avalanche Detectors (CRADs) with combined
THGEM/GAPD multiplier have become an emerging potential technique for dark matter search
and coherent neutrino-nucleus scattering experiments. In such a multiplier the THGEM hole
avalanches are optically recorded in the Near Infrared (NIR) using a matrix of Geiger-mode APDs
(GAPDs). To select the proper sensor, the performances of six GAPD types manufactured by
different companies, namely by Hamamatsu (MPPCs), CPTA (MRS APDs) and SensL (SiPMs),
have been comparatively studied at cryogenic temperatures when operated in two-phase CRADs
in Ar at 87 K. While the GAPDs with ceramic packages failed to operate properly at cryogenic
temperatures, those with plastic packages, namely MPPC S10931-100P and MRS APD 149-35,
showed satisfactory performances at 87 K. In addition, MPPC S10931-100P turned out to be
superior in terms of the higher detection efficiency, lower nose rate, lower pixel quenching
resistor and better characteristics reproducibility.
KEYWORDS: MPPCs, MRS APDs and SiPMs at cryogenic temperatures; Cryogenic avalanche
detectors (CRADs)
*
Corresponding author.
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2015) 1–7
arXiv:1502.03653v1 [physics.ins-det] 12 Feb 2015
Status of the CUORE and results from the CUORE-0 neutrinoless double beta
decay experiments
M. Sistia,b,∗, D. R. Artusac,e , F. T. Avignone IIIc , O. Azzolinid , M. Balatae , T. I. Banksf,g,e , G. Barih , J. Beemani ,
F. Bellinij,k , A. Bersanim , M. Biassonia,b , C. Brofferioa,b , C. Buccie , X. Z. Cain , A. Camachod , A. Caminatam ,
L. Canonicae , X. G. Caon , S. Capellia,b , L. Cappellie,af , L. Carboneb , L. Cardanij,k , N. Casalie , L. Cassinaa,b ,
D. Chiesaa,b , N. Chottc , M. Clemenzaa,b , S. Copellol , C. Cosmellij,k , O. Cremonesib , R. J. Creswickc , J. S. Cushmano ,
I. Dafineik , A. Dallyp , V. Datskovb , S. Dell’Oroe , M. M. Deninnoh , S. Di Domiziol,m , M. L. di Vacrie , A. Drobizhevf ,
L. Ejzakp , D. Q. Fangn , H. A. Farachc , M. Faverzania,b , G. Fernandesl,m , E. Ferria,b , F. Ferronij,k , E. Fiorinib,a ,
M. A. Franceschiq , S. J. Freedmang,f,1 , B. K. Fujikawag , A. Giacheroa,b , L. Gironia,b , A. Giulianir , P. Gorlae ,
C. Gottia,b , T. D. Gutierrezs , E. E. Halleri,t , K. Hang , K. M. Heegero , R. Hennings-Yeomansf , K. P. Hickersonu ,
H. Z. Huangu , R. Kadelv , G. Keppeld , Yu. G. Kolomenskyf,g , Y. L. Lin , C. Ligiq , K. E. Limo , X. Liuu , Y. G. Man ,
C. Maianoa,b , M. Mainoa,b , M. Martinezw , R. H. Maruyamao , Y. Meig , N. Moggih , S. Morgantik , T. Napolitanoq ,
M. Nastasia,b , S. Nisie , C. Nonesx , E. B. Normany,z , A. Nucciottia,b , T. O’Donnellf , F. Oriok , D. Orlandie ,
J. L. Ouelletf,g , C. E. Pagliaronee,af , M. Pallavicinil,m , V. Palmierid , L. Pattavinae , M. Pavana,b , M. Pedrettiy ,
G. Pessinab , V. Pettinaccik , G. Pipernoj,k , C. Pirad , S. Pirroe , S. Pozzia,b , E. Previtalib , C. Rosenfeldc , C. Rusconib ,
E. Salaa,b , S. Sangiorgioy , N. D. Scielzoy , A. R. Smithg , L. Taffarelloaa , M. Tenconir , F. Terranovaa,b , W. D. Tiann ,
C. Tomeik , S. Trentalangeu , G. Venturaab,ac , M. Vignatij,k , B. S. Wangy,z , H. W. Wangn , L. Wielgusp , J. Wilsonc ,
L. A. Winslowu , T. Wiseo,p , A. Woodcraft1 , L. Zanottia,b , C. Zarrae , G. Q. Zhangn , B. X. Zhuu , S. Zucchelliae,h
a Dipartimento
di Fisica, Universit`a di Milano-Bicocca, Milano I-20126 - Italy
b INFN - Sezione di Milano Bicocca, Milano I-20126 - Italy
of Physics and Astronomy, University of South Carolina, Columbia, SC 29208 - USA
- Laboratori Nazionali di Legnaro, Legnaro (Padova) I-35020 - Italy
e INFN - Laboratori Nazionali del Gran Sasso, Assergi (L’Aquila) I-67010 - Italy
f Department of Physics, University of California, Berkeley, CA 94720 - USA
g Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 - USA
h INFN - Sezione di Bologna, Bologna I-40127 - Italy
i Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 - USA
j Dipartimento di Fisica, Sapienza Universit`
a di Roma, Roma I-00185 - Italy
k INFN - Sezione di Roma, Roma I-00185 - Italy
l Dipartimento di Fisica, Universit`
a di Genova, Genova I-16146 - Italy
m INFN - Sezione di Genova, Genova I-16146 - Italy
n Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 - China
o Department of Physics, Yale University, New Haven, CT 06520 - USA
p Department of Physics, University of Wisconsin, Madison, WI 53706 - USA
q INFN - Laboratori Nazionali di Frascati, Frascati (Roma) I-00044 - Italy
r Centre de Spectrom´
etrie Nucl´eaire et de Spectrom´etrie de Masse, 91405 Orsay Campus - France
s Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407 - USA
t Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 - USA
u Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 - USA
v Physics Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 - USA
w Laboratorio de Fisica Nuclear y Astroparticulas, Universidad de Zaragoza, Zaragoza 50009 - Spain
x Service de Physique des Particules, CEA/Saclay, 91191 Gif-sur-Yvette - France
y Lawrence Livermore National Laboratory, Livermore, CA 94550 - USA
z Department of Nuclear Engineering, University of California, Berkeley, CA 94720 - USA
aa INFN - Sezione di Padova, Padova I-35131 - Italy
c Department
d INFN
∗ Corresponding
author
Email address: [email protected] (M. Sisti)
1 Deceased
M. Sisti et al. / Nuclear Physics B Proceedings Supplement 00 (2015) 1–7
2
ab Dipartimento
af
di Fisica, Universit`a di Firenze, Firenze I-50125 - Italy
ac INFN - Sezione di Firenze, Firenze I-50125 - Italy
ad SUPA, Institute for Astronomy, University of Edimburgh, Blackford Hill, Edinburgh EH93HJ - UK
ae Dipartimento di Fisica, Universit`
a di Bologna, Bologna I-40127 - Italy
Dipartimento di Ingegneria Civile e Meccanica, Universit degli Studi di Cassino e del Lazio Meridionale, Cassino I-03043 Italy
Abstract
CUORE is a 741 kg array of TeO2 bolometers for the search of neutrinoless double beta decay of 130 Te. The detector
is being constructed at the Laboratori Nazionali del Gran Sasso, Italy, where it will start taking data in 2015. If the
target background of 0.01 counts/(keV·kg·y) will be reached, in five years of data taking CUORE will have a 1σ half
life sensitivity of 1026 y. CUORE-0 is a smaller experiment constructed to test and demonstrate the performances
expected for CUORE. The detector is a single tower of 52 CUORE-like bolometers that started taking data in spring
2013. The status and perspectives of CUORE will be discussed, and the first CUORE-0 data will be presented.
Keywords: Double beta decay, Neutrino mass, Bolometers
1. Introduction
Neutrinos are massive particles. A beautiful proof of
this important property was obtained by neutrino oscillation experiments more than a decade ago. Since then,
the key role of neutrinoless double beta decay searches
has been established, as attested by the growing number
of experimental proposals in the last years.
Neutrinoless double beta decay (ββ0ν) is a proposed
very rare nuclear process in which a nucleus transforms
into its (A, Z+2) isobar with the emission of two electrons. While the two neutrino channel (ββ2ν) – where
two neutrinos are contemporary emitted in the decay – is
allowed by the Standard Model of Particle Physics and
has been observed experimentally in a dozen of isotopes
with half-lives of the order 1018 − 1021 y, the neutrinoless mode is a lepton number violating process which
can occur only if the Majorana character of the neutrino is allowed. Therefore, ββ0ν offers a unique experimental chance to investigate still unresolved fundamental questions, since its observation would undoubtedly
unveil the neutrino character, confirm lepton number violation and allow to assess the absolute neutrino mass
scale with high sensitivity, thus helping point us towards
the proper extension of the Standard Model [1–3].
Neutrinoless double beta decay can proceed via different mechanisms: in the case of a virtual exchange of
a light Majorana neutrino between the two nucleons, the
decay rate is proportional to the square of the so-called
effective Majorana mass |hmββ i| (a coherent sum of neutrino mass eigenstates) [4]:
0ν −1
[T 1/2
] =
|hmββ i|2 0ν 0ν 2
G |M |
m2e
(1)
0ν
where T 1/2
is the decay half-life, G0ν is the two-body
phase-space integral, M 0ν is the ββ0ν Nuclear Matrix
Element (NME), and me is the electron mass. The product F N0ν = G0ν |M 0ν |2 includes all the nuclear details of
the decay and it is usually referred to as nuclear factor
of merit. While G0ν can be calculated with reasonable
accuracy, the NME value is strongly dependent on the
nuclear model used for its evaluation so that discrepancies of about a factor 2-3 among the various theoretical
calculations may be found [5–14]. Such uncertainties
are of course reflected on the |hmββ i| inferred values.
Experimentally one measures the energy deposited
by the two electrons, which result in a peak centered at
the ββ0ν candidate isotope transition energy (Qββ ). For
neutrino masses in the Inverted Hierarchy region, halflives in the range 1026 − 1027 y are expected for several ββ0ν candidates [15]. This implies a few decays
per 100 kg of candidate isotope per year. In a realistic
experiment this faint signal must be singled out among
the background events in the energy region around Qββ .
Hence, the sensitivity of a given experiment critically
depends on the number of spurious counts in the region
of interest: for a 68% confidence level, it is defined as
the decay half-life corresponding to the maximum signal that√could be hidden by a 1σ background fluctuation
nB = BT ∆M, where ∆ is the FWHM energy resolution, M is the detector mass, T is the measuring time,
and B is the background per unit mass, energy, and time.
The experimental figure of merit is thus given by:
r
ln 2Nββ T
MT
Back.Fluct.
F 0ν = T 1/2
=
∝ η
(2)
nB
B∆
where Nββ is the number of ββ0ν decaying nuclei un-
arXiv:1502.03535v1 [physics.ins-det] 12 Feb 2015
Reducing DRIFT Backgrounds with a Submicron
Aluminized-Mylar Cathode
J.B.R. Battata , E. Dawb , A. Dorofeevc , A.C. Ezeribeb , J.R. Foxd , J.-L.
Gauvreaud , M. Golde , L. Harmond , J. Hartonc , R. Laflere , R.J. Lauere , E.R.
Leee , D. Loombae , A. Lumnahd , J. Matthewse , E.H. Millere,∗, F. Moutonb ,
A.St.J. Murphyf , N. Phane , S.W. Sadlerb , A. Scarffb , F.G. Schuckman IIc ,
D. Snowden-Ifftd , N.J.C. Spoonerb , D. Walkerb
a
Department of Physics, Wellesley College, MA 02481, USA
Department of Physics and Astronomy, University of Sheffield, S3 7RH, UK
c
Department of Physics, Colorado State University, CO 80523, USA
d
Department of Physics, Occidental College, Los Angeles, CA 90041, USA
e
Department of Physics and Astronomy, University of New Mexico, NM 87131, USA
f
SUPA, School of Physics and Astronomy, University of Edinburgh, EH9 3JZ, UK
b
Abstract
Background events in the DRIFT-IId dark matter detector, mimicking potential WIMP signals, are predominantly caused by alpha decays on the central
cathode in which the alpha particle is completely or partially absorbed by
the cathode material. We installed a 0.9 µm thick aluminized-mylar cathode as a way to reduce the probability of producing these backgrounds. We
study three generations of cathode (wire, thin-film, and radiologically clean
thin-film) with a focus on the ratio of background events to alpha decays.
Two independent methods of measuring the absolute alpha decay rate are
used to ensure an accurate result, and agree to within 10%. Using alpha
range spectroscopy, we measure the radiologically cleanest cathode version
to have a contamination of 3.3 ± 0.1 ppt 234 U and 73 ± 2 ppb 238 U. This
cathode reduces the probability of producing an RPR from an alpha decay
by a factor of 70 ± 20 compared to the original stainless steel wire cathode. First results are presented from a texturized version of the cathode,
intended to be even more transparent to alpha particles. These efforts, along
∗
Corresponding author
Email address: [email protected], +016175714847 (E.H. Miller)
Preprint submitted to Nuclear Instruments and Methods A
February 13, 2015
Toward a solution to the RAA and v2 puzzle for heavy quarks
Santosh K. Dasa,b , Francesco Scardinaa,b , Salvatore Plumaria,b , Vincenzo Grecoa,b
a
arXiv:1502.03757v1 [nucl-th] 12 Feb 2015
b
Department of Physics and Astronomy, University of Catania,
Via S. Sofia 64, 1-95125 Catania, Italy and
Laboratori Nazionali del Sud, INFN-LNS, Via S. Sofia 62, I-95123 Catania, Italy
(Dated:)
The heavy quarks constitutes a unique probe of the quark-gluon plasma properties. Both at RHIC
and LHC energies a puzzling relation between the nuclear modification factor RAA (pT ) and the elliptic flow v2 (pT ) has been observed which challenged all the existing models, especially for D mesons.
We discuss how the temperature dependence of the heavy quark drag coefficient is responsible to
address for a large part of such a puzzle. In particular, we have considered four different models to
evaluate the temperature dependence of drag and diffusion coefficients propagating through a quark
gluon plasma (QGP). All the four different models are set to reproduce the same RAA (pT ) observed
in experiments at RHIC and LHC energy. We point out that for the same RAA (pT ) one can generate
2-3 times more v2 depending on the temperature dependence of the heavy quark drag coefficient.
An increasing drag coefficient as T → Tc is a major ingredient for a simultaneous description of
RAA (pT ) and v2 (pT ).
PACS: 25.75.-q; 24.85.+p; 05.20.Dd; 12.38.Mh
The ongoing nuclear collision programs at Relativistic Heavy Ion Collider (RHIC) and Large
Hadron Collider (LHC) energies are expected to create a medium that behaves like a nearly perfect fluid,
where the bulk properties of the matter are governed by the light quarks and gluons called Quark
Gluon Plasma (QGP) [1, 2]. To characterize the
QGP, penetrating and well calibrated probes are essential. In this context, the heavy quarks (HQs),
mainly charm and bottom quarks, play a vital role
since they do not constitute the bulk part of the
matter owing to their larger mass compared to the
temperature created in ultra-relativistic heavy-ion
collisions (uRHIC’s) [3].
There are presently two main observables related
with heavy quarks that have been measured at both
RHIC and LHC energies. The first one is the socalled nuclear suppression factor RAA that is the ratio between the pT spectra of heavy flavored hadrons
(D and B) produced in nucleus + nucleus collisions
with respect to those produced in proton + proton collisions. More specifically at RHIC until recently has not been possible to measure directly D
and B but only the leptons through their semileptonic decays. The other key observable is the elliptic
flow v2 = hcos(2φp )i, a measure of the anisotropy
in the angular distribution that corresponds to the
anisotropic emission of particles with respect to the
azimuthal angle φp . Despite their large mass, experimentally measured nuclear suppression factor RAA
and elliptic flow v2 of the heavy mesons are comparable to that of light hadrons [17–20]. This is in
contrast to the expectations drawn initially from the
perturbative interaction of HQs with the medium
which predicted a RAA ≈ 0.6 for charm quarks,
RAA ≈ 0.8 − 0.9 for bottom quarks in the central
collisions [11, 12] at intermediate pT . Also the v2
was predicted to be much smaller with respect to
the light hadron ones [12].
Several theoretical efforts have been made in order to calculate the experimentally observed RAA
[17–20] and v2 [17] for the non-photonic single electron spectra within the Fokker-Planck approach [7–
10, 15, 21, 24, 26, 34–37] and relativistic Boltzmann
transport approach [16, 29–33, 49, 50]. Furthermore, also in a pQCD framework supplemented by
the hard thermal loop scheme several advances have
been made to evaluate realistic Debye mass and running coupling constants [16, 26] and three-body scattering effects [10, 21, 22, 25] have been implemented .
It has been show [38] that the inclusion of both elastic and inelastic collisions with a dynamical energy
loss formalism reduces the gap between the theoretical and experimental results for RAA as pT → 5
GeV [39, 40]. Several other improvements have been
purposed [41–43] to advance the description of the
data. Interaction from AdS/CFT [54] have also been
implemented [24, 28, 56] to study the heavy flavor dynamics at RHIC and LHC. Essentially all the
models show some difficulties to describe simultaneously both RAA (pT ) and v2 (pT ) and such a trait
is not only present at RHIC energy but also in the
results coming from collisions at LHC energy [20].
In this letter we will address the impact of the
temperature dependence of the interaction (drag coefficient) on RAA and v2 relation simultaneously. For
this we are considering four different models having
different T dependent drag coefficients. For the momentum evolution of the HQ, we are using 3+1 D
Langevin dynamics. We notice that the several approaches and modelings of the HQ in-medium interaction differs significantly for the T dependence of
the drag coefficient they entail. One can go from a
T 2 dependence of the AdS/CFT approach to a drag
Crosstalk between DGP branes
Rainer Dick
arXiv:1502.03754v1 [hep-th] 12 Feb 2015
Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Canada SK S7N 5E2
and
Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Canada ON N2L 2Y5
Abstract
If two DGP branes carry U(1) gauge theories and overlap, particles of one brane can interact with the photons from
the other brane. This coupling modifies in particular the Coulomb potentials between charges from the same brane
in the overlapping regions. The coupling also introduces Coulomb interactions between charges from the different
branes which can generate exotic bound states.
The effective modification of the fine structure constant in the overlap region generates a trough in signals at the
redshift of the overlap region and an increase at smaller or larger redshift, depending on the value of the crosstalk
parameter ge g p . This implies potentially observable perturbations in the Lyman α forest if our 3-brane overlapped
with another 3-brane in a region with redshift z . 6. Crosstalk can also affect structure formation by enhancing or
suppressing radiative cooling.
Keywords: Extensions of the Standard Model, Branes, Extra dimensions, Lyman α forest
PACS: 11.25.-w, 12.60.-i, 14.80.Rt, 98.58.Db, 98.62.Ra
2000 MSC: 83.E15, 81.T30
Shortly after the inception of DGP branes, it was
pointed out that at least at the classical level they can
support a modified Friedmann equation which may explain accelerated expansion without dark energy [5, 6].
Stability of the self-accelerated solution has meanwhile
been called into question [7], but DGP branes can nevertheless support consistent modified cosmological evolution equations which comply with standard late time
FLRW evolution [5, 6, 8, 9]. On the other hand, it was
found in [8] and rediscovered in [10] that DGP branes
can even support the standard Friedmann equation and
all the corresponding standard cosmological models on
the brane, i.e. absence of cosmological signals from
modified evolution equations does not rule out DGP
branes. It is therefore important to also look for other
possible experimental signatures of DGP branes.
1. Introduction
The idea of extra dimensions has been around in theoretical physics for almost a century [1] and has been
considerably expanded and reinvigorated in string theory. Furthermore, Dvali, Gabadadze and Porrati (DGP)
pointed out in 2000 that we could live in a higherdimensional world with infinitely large extra dimensions hidden from plain sight because everything except
gravity can only propagate on a 3-brane in the higherdimensional world [2, 3]. The idea that observation of
additional dimensions does not need to be suppressed
by energy thresholds, but that instead there can be consistent restrictions of matter fields to submanifolds of a
higher-dimensional universe was a significant advancement of our understanding of higher dimensions. Therefore we denote a 3-brane carrying matter fields in an
ambient spacetime with gravitational degrees of freedom as a DGP brane, including also e.g. 3-branes in
cascading gravity models [4]. At this point we do not
specify the background gravitational theory because we
are interested in electromagnetic effects on the branes.
In the present paper I would like to draw attention to
the fact that overlap of DGP branes at or after reionization can generate perturbations in the Lyman α forest in
the direction of the overlap region. This is based on the
observation that particles from our brane can couple to
photons from a U(1) gauge theory on the second brane,
thus impacting Coulomb interactions in the overlap region. This phenomenon of possible mixing of gauge
Email address: [email protected] (Rainer Dick)
1
arXiv:1502.03689v1 [nucl-th] 12 Feb 2015
Charge splitting of directed flow and
charge-dependent effects in pion spectra in heavy
ion collisions
A. Rybicki1 , A. Szczurek1,2 , M. Klusek-Gawenda1 , M. Kielbowicz3
1
H.Niewodnicza´nski Institute of Nuclear Physics, Polish Academy
of Sciences, Radzikowskiego 152, 31-342 Krak´ow, Poland
2
University of Rzesz´ow, Rejtana 16, 35-959 Rzesz´ow, Poland
3
The Tadeusz Ko´sciuszko Cracow University of Technology,
Warszawska 24, 31-155 Krak´ow, Poland
February 13, 2015
Abstract
The large and rapidly varying electric and magnetic fields induced by
the spectator systems moving at ultrarelativistic velocities induce a charge
splitting of directed flow, v1 , of positive and negative pions in the final state
of the heavy ion collision. The same effect results in a very sizeable distortion
of charged pion spectra as well as ratios of charged pions (π + /π − ) emitted at
high values of rapidity. Both phenomena are sensitive to the actual distance
between the pion emission site and the spectator system. This distance dE
appears to decrease with increasing rapidity of the pion, and comes below
∼1 fm for pions emitted close to beam rapidity. In this paper we discuss
how these findings can shed new light on the space-time evolution of pion
production as a function of rapidity, and on the longitudinal evolution of the
system created in heavy ion collisions.
1
The critical behavior of hadronic matter:
Comparison of lattice and bootstrap model calculations∗
L. Turko†
Institute of Theoretical Physics, University of Wroclaw, pl. Maksa Borna 9, 50-204 Wroclaw, Poland
Statistical bootstrap model and the related concept of the limiting temperature begun the discussion about phase transitions in the hadronic matter. This was also the origin of the quark-gluon
plazma concept. We discuss here to which extend lattice studies of QCD critical behavior at non-zero
chemical potential are compatible with the statistical bootstrap model calculations.
Keywords: Statistical bootstrap model, lattice QCD thermodynamics, critical temperature
arXiv:1502.03647v1 [hep-lat] 12 Feb 2015
I.
ROLF HAGEDORN - SOME PERSONAL IMPRESSIONS
”A fireball consists of fireballs, which in turn consist of fireballs, and so on. . . .” - that was the leading sentence
from the famous CERN Yellow Report 71-12 where Rolf Hagedorn presented in details leading ideas and results of
his Statistical Bootstrap Model (SBM)[1]. I met this Report in late 70’ having yet some scientific experience both in
quantum field theory as well as in the theory of high energy multiproduction processes. Starting from the beginning
I’ve realized that I was reading something unusual. I was impressed by the elegance and precision of the presentation.
It was quite obvious for me that the author had spent a lot of time on discussions to clarify his arguments. Some
questions were answered before I could even think about them. All was achieved without overusing of mathematical
formalism, although all presentation was mathematically very rigorous. The author, however, used as simple and
natural mathematical tools as possible, without going into complex jungle of formulae and multilevel definitions. It
was also clear visible that the model, all its architecture and equipment is a one man project - Rolf Hagedorn.
And the most important point - the new idea was presented. I was not sure at that time - is this right or wrong one
- but that was the idea not to be ignored. It was a nice answer for the long standing question - how effectively describe
basic structure of matter, i.e. here hadronic matter. We knew the whole hierarchy - nuclei, nucleons, elementary
particles, quarks Any if those levels pretended at some time to be the ”real” elementary one. The SBM didn’t try to
answer for the question about basic constituents. It just pointed out that this would be a wrong question.
I met Rolf Hagedorn in CERN in 1979. It was about two years later. I was quite convinced yet that time to the
idea of statistical bootstrap. I saw there also a good place to continue - at least as the way of thinking. I tried also
to get some deeper knowledge of statistical physics which was earlier for me rather obscure subject in the domain of
strong interactions. I also convinced my PhD student at that time, Krzysztof Redlich, that this mixture of statistical
physics and theory of elementary particles could be a very fruitful and interesting subject. Traveling to CERN I was
quite excited to meet the physicist whose papers were giving me not only scientific but also quite esthetic experience.
In short: personal meetings with Hagedorn were even more interesting then reading his papers. He was a man of
great general culture, very polite but also expecting well prepared arguments in discussions. From other side he was
very open to present his reasoning, his calculations - even those being on a preliminary level. His hand-written notes
were famous - in an almost calligraphic script, nicely written formulae, alternative arguments. He handed those notes
to collaborators - it was as you received a chapter of an advanced textbook.
After two years our relations rapidly changed. The martial law, introduced in Poland in December 1981, not only
made impossible my stay in CERN expected on Spring 1982, but also put me first in internee camp, then in jail. I
was not only scientist at that time who found himself in such a unexpected surrounding. And it was Rolf Hagedorn,
who without any delay, just in first days of martial low, co-initiated in CERN campaign to free internee or jailed
physicists in Poland. Posters with photos and names were posted on walls of TH division, signatures of protest were
collected, letters of protest were sent to Polish officials.
When we met again in 1989 we still kept our relations, not only on scientific but also on a friendly level. Looking
now back I must admit that Rolf Hagedorn was among those who shaped my profile - not only as a scientist, but also
as a man. He was definitely worth to follow - in any respect. I am very happy I had the possibility to be close with
such an exceptional scientist and an exceptional man. Man of honor.
∗
to appear in R. Hagedorn and J. Rafelski (Ed.), ”Melting Hadrons, Boiling Quarks”, Springer Verlag 2015
address: [email protected]
† Electronic
Symmetry improvement of 3PI effective actions for O (N) scalar field theory
Michael J. Brown and Ian B. Whittingham
arXiv:1502.03640v1 [hep-th] 12 Feb 2015
College of Science, Technology and Engineering, James Cook University, Townsville 4811, Australia∗
(Dated: February 12, 2015)
n-Particle Irreducible Effective Actions (nPIEA) are a powerful tool for extracting nonperturbative and non-equilibrium physics from quantum field theories. Unfortunately, practical
truncations of nPIEA can unphysically violate symmetries. Pilaftsis and Teresi (PT) addressed this
by introducing a “symmetry improvement” scheme in the context of the 2PIEA for an O (2) scalar
theory, ensuring that the Goldstone boson is massless in the broken symmetry phase [A. Pilaftsis
and D. Teresi, Nuclear Physics B 874, 2 (2013), pp. 594–619.]. We extend this idea by introducing
a symmetry improved 3PIEA for O (N ) theories, for which the basic variables are the one-, twoand three-point correlation functions. This requires the imposition of a Ward identity involving the
three-point function. We find that the method leads to an infinity of physically distinct schemes,
though a field theoretic analogue of d’Alembert’s principle is used to single out a unique scheme.
The standard equivalence hierarchy of nPIEA no longer holds with symmetry improvement and we
investigate the difference between the symmetry improved 3PIEA and 2PIEA. We present renormalized equations of motion and counter-terms for two and three loop truncations of the effective
action, though we leave their numerical solution to future work. We solve the Hartree-Fock approximation and find that our method achieves a middle ground between the unimproved 2PIEA and
PT methods. The phase transition predicted by our method is weakly first order and the Goldstone
theorem is satisfied, while the PT method correctly predicts a second order phase transition. In
contrast, the unimproved 2PIEA predicts a strong first order transition with large violations of the
Goldstone theorem. We also show that, in contrast to PT, the two loop truncation of the symmetry
improved 3PIEA does not predict the correct Higgs decay rate although the three loop truncation
does, at least to leading order. These results suggest that symmetry improvement should not be
applied to nPIEA truncated to < n loops. We also show that symmetry improvement schemes are
compatible with the Coleman-Mermin-Wagner theorem, giving a check on the consistency of the
formalism.
PACS numbers: 11.15.Tk, 11.30.-j, 05.10.-a
Keywords: nPI effective action, symmetry improvement, scalar field theory
I.
INTRODUCTION
The recent demands of non-equilibrium field theory applications in particle physics, cosmology and condensed
matter have led to a renaissance in the development of
novel field theory methods. The S-matrix school, rebooted in the guise of spinor-helicity methods, has led to
a dramatic speedup in the computation of gauge theory scattering amplitudes in vacuum [1]. On the finite temperature and density fronts, efficient functional
methods in the form of n-particle irreducible effective
actions (nPIEA) have proven useful to understand collective behaviour and phase transitions [2]. They are
similar in spirit to methods based on Schwinger-Dyson
equations in field theory or BBGKY (Bogoliubov-BornGreen-Kirkwood-Yvon) equations in kinetic theory however, unlike the Schwinger-Dyson or BBGKY equations,
nPIEA naturally form closed systems of equations of motion without requiring any closure ansatz [3–5]. nPIEA
methods can be understood as a hybrid of variational
and perturbative methods: nPIEA consist of a series of
Feynman diagrams, however the propagators and vertices of these diagrams are the exact 1- through n-point
∗
[email protected]
proper connected correlation functions which are determined self-consistently using variational equations of motion.
This self-consistency effectively resums certain classes
of perturbative Feynman diagrams to infinite order. For
example, the one loop 2PIEA diagram corresponding to
the Hartree-Fock self-energy in φ4 theory actually sums
all of the so-called daisy and super-daisy graphs of ordinary perturbation theory (Figure I.1). This particular
resummation is often done in the literature without the
use of nPIEA, but such ad hoc resummation schemes run
the risk of summing an asymptotic series: a mathematically dangerous operation (recent progress on summability has been made in resurgence theory [6], which is
beyond the scope of this work). nPIEA sidestep this issue
because they are defined by the rigorous Legendre transform procedure, guaranteeing equivalence with the original theory. Unlike ad hoc resummations, nPIEA based
approximation schemes are placed on a firm theoretical
footing and can be systematically improved.
However, loop-wise truncations of nPIEA, n > 1,
have difficulties in the treatment of theories with spontaneously broken continuous symmetries. The root cause
of these difficulties is the fact that nPIEA obey different
Ward identities than the 1PIEA. When the effective action is truncated to a finite order the equivalence between
the Ward identities is lost. This can also be understood
Nucleons and parity doubling across the deconfinement transition
Gert Aartsa , Chris Alltona , Simon Handsa , Benjamin J¨agera, Chrisanthi Prakia, and Jon-Ivar Skullerudb
b
a
Department of Physics, College of Science, Swansea University, Swansea SA2 8PP, United Kingdom and
Department of Mathematical Physics, National University of Ireland Maynooth, Maynooth, County Kildare, Ireland
(Dated: February 13, 2015)
arXiv:1502.03603v1 [hep-lat] 12 Feb 2015
It is expected that nucleons and their parity partners become degenerate when chiral symmetry
is restored. We investigate this question in the context of the thermal transition from the hadronic
phase to the quark-gluon plasma, using lattice QCD simulations with Nf = 2 + 1 flavours. We
observe a clear sign of parity doubling in the quark-gluon plasma. Besides, we find that the nucleon
ground state is, within the uncertainty, largely independent of the temperature, whereas temperature
effects are substantial in the negative-parity (N ∗ ) channel, already in the confined phase.
Introduction – The role of discrete and continuous symmetries played a fundamental role in the development of
the theory of the strong interaction, Quantum Chromodynamics. Chiral symmetry breaking and its restoration
remain topical subjects, mostly due to the creation of
the quark-gluon plasma at relativistic heavy-ion collision
experiments at the Large Hadron Collider (CERN) and
the Relativistic Heavy Ion Collider (BNL). It is expected
that chiral symmetry will be restored at high temperature, as seen e.g. in nonperturbative studies using lattice
QCD simulations [1, 2]. The combination of the discrete
symmetries parity P and charge conjugation C yields the
still unsolved strong CP problem.
In the past decades chiral symmetry restoration at finite temperature has been studied in great detail in the
mesonic sector [3]. One reason is that mesonic correlation
functions are relatively easily accessible on the lattice
[4, 5]. Moreover, susceptibilities related by chiral symmetry, such as in the pion and scalar meson channels, can
now be computed using chiral lattice fermions [6]. Unlike the mesonic sector, the baryonic sector has hardly
been investigated at finite temperature (early work on
screening masses from lattice QCD can be found in Ref.
[7], and, in the presence of a small chemical potential,
in Ref. [8]). Nevertheless, understanding the behaviour
of nucleons in a hadronic medium or in the quark-gluon
plasma is relevant for heavy-ion collisions, where proton
spectra are routinely measured and compared to theoretical predictions. Just as for mesons, possible in-medium
modification of nucleons and other baryons might affect
signals observed in those experiments.
In the baryon sector the combination of chiral symmetry and parity leads to a prediction readily testable in
QCD: namely that of parity doubling, i.e., a degeneracy
between channels related by parity, provided that both
symmetries are realised (the argument will be briefly reviewed below). At zero temperature, where chiral symmetry is broken, parity doubling is not observed, except
perhaps in the case of excited hadrons [9]. However,
since chiral symmetry is restored at high temperature,
it should become relevant in the quark-gluon plasma.
Recently the question of parity doubling has been
taken up in Ref. [10], where it was studied at three tem-
peratures in quenched lattice QCD. In this paper we
present what is, as far as we know, the first study of nucleons at finite temperature in lattice QCD with Nf = 2 + 1
dynamical quarks, for a range of temperatures below and
above the deconfinement transition. We find clear indications of parity doubling, occurring in coincidence with
the deconfinement crossover. Moreover, within our numerical uncertainty, the mass of the nucleon ground state
is found to be independent of the temperature of the
hadronic medium.
Nucleon propagation – The standard interpolation operator for a nucleon, which we will consider below, is
given by (the material reviewed here is well-known, see
e.g. the textbooks [11, 12])
ON (x, τ ) = ǫabc ua (x, τ ) uTb (x, τ )Cγ5 dc (x, τ ) ,
(1)
where u, d are the quark fields, a, b, c are colour indices,
other indices are suppressed and C denotes the charge
conjugation matrix. Under parity one finds that
PON (x, τ ) = γ4 ON (−x, τ ),
(2)
and hence operators for the positive and negative parity
channels are obtained as
ON± (x, τ ) = P± ON (x, τ ),
P± =
1
(1 ± γ4 ).
2
(3)
We consider the usual euclidean correlators, projected to
zero momentum,
Z
(4)
G± (τ ) = d3 x ON± (x, τ )O N± (0, 0) .
It follows from the properties under euclidean time reflection that, in the case of G+ (τ ), forward (backward)
propagation in time corresponds to the positive-parity
(negative-parity) channel. On a lattice at a nonzero temperature T , with 0 ≤ τ < 1/T , the negative-parity channel is then propagating with τ− = 1/T − τ . Hence both
parity channels can be obtained from the same correlator, either G+ (τ ) or G− (τ ). In the case that the signal
is dominated by the ground states in both channels, this
leads to the simple exponential Ansatz,
G± (τ ) = A± e−m± τ + A∓ e−m∓ (1/T −τ ) ,
(5)
Assessment of molecular effects on neutrino mass measurements
from tritium beta decay
L. I. Bodine,∗ D. S. Parno,† and R. G. H. Robertson‡
Center for Experimental Nuclear Physics and Astrophysics,
and Department of Physics, University of Washington, Seattle WA 98195, USA
arXiv:1502.03497v1 [nucl-ex] 12 Feb 2015
Abstract
The beta decay of molecular tritium currently provides the highest sensitivity in laboratory-based
neutrino mass measurements. The upcoming Karlsruhe Tritium Neutrino (KATRIN) experiment
will improve the sensitivity to 0.2 eV, making a percent-level quantitative understanding of molecular effects essential. The modern theoretical calculations available for neutrino-mass experiments
agree with spectroscopic data. Moreover, when neutrino-mass experiments performed in the 1980s
with gaseous tritium are re-evaluated using these modern calculations, the extracted neutrino masssquared values are consistent with zero instead of being significantly negative. On the other hand,
the calculated molecular final-state branching ratios are in tension with dissociation experiments
performed in the 1950s. We re-examine the theory of the final-state spectrum of molecular tritium
decay and its effect on the determination of the neutrino mass, with an emphasis on the role of the
vibrational- and rotational-state distribution in the ground electronic state. General features can
be reproduced quantitatively from considerations of kinematics and zero-point motion. We summarize the status of validation efforts and suggest means for resolving the apparent discrepancy in
dissociation rates.
∗
†
‡
corresponding author: [email protected]
[email protected]
[email protected]
1
Consistently violating the non-Gaussian
consistency relation
arXiv:1502.03458v1 [astro-ph.CO] 11 Feb 2015
Sander Mooija, Gonzalo A. Palmaa and Antonio E. Romanob,c
a Grupo
de Cosmolog´ıa y Astrof´ısica Te´
orica,
Departamento de F´ısica, FCFM, Universidad de Chile
Blanco Encalada 2008, Santiago, Chile
b Instituto de F´
ısica, Universidad de Antioquia, A.A.1226, Medellin, Colombia
c Department of Physics, University of Crete,
71003 Heraklion,Greece
Abstract
Non-attractor models of inflation are characterized by the super-horizon evolution of
curvature perturbations, introducing a violation of the non-Gaussian consistency relation
between the bispectrum’s squeezed limit and the power spectrum’s spectral index. In this
work we show that the bispectrum’s squeezed limit of non-attractor models continues to
respect a relation dictated by the evolution of the background. We show how to derive
this relation using only symmetry arguments, without ever needing to solve the equations
of motion for the perturbations.
Mon. Not. R. Astron. Soc. 000, 1–17 (2014)
Printed 13 February 2015
(MN LATEX style file v2.2)
Axion dark matter, solitons, and the cusp-core problem
David
J. E. Marsh1? and Ana-Roxana Pop2 †
1
Perimeter Institute, 31 Caroline St N, Waterloo, ON, N2L 6B9, Canada
of Physics, Princeton University, Princeton, NJ 08544, USA
2 Department
arXiv:1502.03456v1 [astro-ph.CO] 11 Feb 2015
Draft version: 13 February 2015
ABSTRACT
Self-gravitating bosonic fields can support stable and localised field configurations. In the case of real fields, these solutions oscillate in time with a given
period and are known as oscillatons. The density profile is static, and is a (nontopological, pseudo-) soliton. Such solitons should be ubiquitous in models of
axion dark matter, with the soliton characteristic mass and size depending on
some inverse power of the axion mass. Stable configurations of non-relativistic
axions are studied numerically using the Schr¨odinger-Poisson system. This
method, and the resulting soliton density profiles, are reviewed. Using a scaling symmetry and the uncertainty principle, the core size of the soliton can
be related to the central density and axion mass, ma , in a universal way. Solitons have a constant central density due to pressure-support, unlike the cuspy
profile formed during structure formation with cold dark matter (CDM). One
consequence of this fact is that solitons composed of ultra-light axions (ULAs)
may resolve the ‘cusp-core’ problem of CDM. In DM halos, thermodynamics
will lead to a CDM-like Navarro-Frenk-White profile at large radii, with a
central soliton core at small radii. Using Monte-Carlo techniques to explore
the possible density profiles of this form, a fit to stellar-kinematical data from
the Fornax and Sculptor dwarf spheroidal galaxies is performed. In order for
ULAs to resolve the cusp-core problem (without recourse to baryon feedback
or other astrophysical effects) the axion mass must satisfy ma < 1.1×10−22 eV
at 95% C.L. On the other hand, ULAs with ma . 1×10−22 eV are in some tension with cosmological structure formation. An axion solution to the cusp-core
problem thus makes novel predictions for future measurements of the epoch
of reionisation. On the other hand, this can be seen as evidence that structure
formation could soon impose a Catch 22 on axion/scalar field DM, similar to
the case of warm DM. A number of ways to further test these scenarios are
suggested.
Key words: Cosmology: theory, dark matter, elementary particles – galaxies:
dwarf, halos.
1
INTRODUCTION
Dark matter (DM) is known to comprise the majority of
the matter content of the universe (e.g. Planck Collaboration 2014, 2015). The simplest and leading candidate
is cold (C)DM. CDM has vanishing equation of state
and sound speed, w = c2s = 0, and clusters on all scales.
Popular CDM candidates are O(GeV) mass thermally
?
E-mail: [email protected]
† E-mail: [email protected]
c 2014 RAS
produced supersymmetric weakly interacting massive
particles (SUSY WIMPs, e.g. Jungman et al. 1996), and
the O(µeV) mass non-thermally produced QCD axion
(Peccei & Quinn 1977; Weinberg 1978; Wilczek 1978).
The free-streaming and decoupling lengths of a WIMP,
and the Jeans scale of the QCD axion are both extremely small (i.e. sub-solar on a mass scale, see e.g.
Loeb & Zaldarriaga 2005).
It is well known, however, that CDM faces a number of ‘small-scale’ problems related to galaxy formation: ‘missing satellites’ (Moore et al. 1999; Klypin et al.
Interplay of relativistic and nonrelativistic transport in atomically precise segmented
graphene nanoribbons
Constantine Yannouleas, Igor Romanovsky, and Uzi Landman
arXiv:1502.00205v1 [cond-mat.mes-hall] 1 Feb 2015
School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430
(Dated: 14 September 2014)
Graphene’s isolation launched explorations of fundamental relativistic physics originating from
the planar honeycomb lattice arrangement of the carbon atoms, and of potential technological
applications in nanoscale electronics. Bottom-up fabricated atomically-precise segmented graphene
nanoribbons, SGNRs, open avenues for studies of electrical transport, coherence, and interference
effects in metallic, semiconducting, and mixed GNRs, with different edge terminations. Conceptual
and practical understanding of electric transport through SGNRs is gained through nonequilibrium
Green’s function (NEGF) conductance calculations and a Dirac continuum model that absorbs the
valence-to-conductance energy gaps as position-dependent masses, including topological-in-origin
mass-barriers at the contacts between segments. The continuum model reproduces the NEGF
results, including optical Dirac Fabry-P´erot (FP) equidistant oscillations for massless relativistic
carriers in metallic armchair SGNRs, and an unequally-spaced FP pattern for mixed armchair-zigzag
SGNRs where carriers transit from a relativistic (armchair) to a nonrelativistic (zigzag) regime. This
provides a unifying framework for analysis of coherent transport phenomena and interpretation of
forthcoming experiments in SGNRs.
Graphene, a single-atom-thin plane of graphite, has
been the focus of intensive research endeavors since its
isolation in 2004.1 The high degree of interest in this material originates from its outstanding electronic, mechanical, and physical properties that result from the planar
arrangement of the carbon atoms in a honeycomb lattice. Indeed graphene is considered both as a vehicle
for exploring fundamental relativistic physics, as well as
a promising material for potential technological applications in nanoscale electronics and optics.2
However, the absence of an electronic energy gap between the valence and conduction bands of 2D graphene
casts doubts on its use in nanoelectronic devices. Nevertheless, theoretical studies had predicted that narrow
graphene nanoribbons (GNRs) can have a large band
gap, comparable to silicon (∼ 1 eV), depending on the
ribbon’s width W and edge geometry (as well as possible doping at controlled positions). Pertinent to our
work, we note that these predictions were made3–7 for
GNRs that have atomically precise armchair edges with
widths W ≤ 2 nm. Consequently, the most recent advent and growing availability of bottom-up fabricated
atomically-precise narrow graphene nanoribbons,8–12 including segmented13 armchair graphene nanoribbons
(SaGNRs), opens promising avenues for graphene nanoelectronics and for detailed explorations of coherent
electrical transport in nanoribbon-based graphene wires,
nanoconstrictions, and quantum-point contacts.
Here we report on the unique apects of transport
through segmented GNRs obtained from tight-binding
non-equilibrium Green’s function14 (TB-NEGF) calculations in conjunction with an analysis based on a onedimensional (1D) relativistic Dirac model. This model
is referred to by us as the Dirac-Fabry-P´erot (DFP)
theory (see below for the choice of name). In particular, it is shown that the valence-to-conduction energy
gap in armchair GNR (aGNR) segments, as well as the
barriers at the interfaces between nanoribbon segments,
can be incorporated in an effective position-dependent
mass term in the Dirac hamiltonian; the transport solutions associated with this hamiltonian exhibit conductance patterns comparable to those obtained from the
microscopic NEGF calculations. For zigzag graphene
nanoribbon (zGNR) segments, the valence-to-conduction
energy gap vanishes, and the mass term is consonant
with excitations corresponding to massive nonrelativistic Schr¨odinger-type carriers.
As aforementioned, transport through narrow
graphene channels − particularly bottom-up fabricated
and atomically-precise graphene nanoribbons8–13 − is
expected to offer ingress to unique behavior of Dirac
electrons in graphene nanostructures. In particular, the
wave nature of elementary particles (e.g., electrons and
photons) is commonly manifested and demonstrated in
transport processes. Because of an exceptionally high
electron mobility and a long mean-free path,1 it has been
anticipated that graphene devices hold the promise for
the realization, measurement, and possible utilization of
fundamental aspects of coherent and ballistic transport
behavior, which to date have been observed, with
varying degrees of success, mainly at semiconductor
interfaces,15,16 quantum point contacts,17 metallic
wires,18 and carbon nanotubes.19 Prominent among the
effects that accompany coherence and ballistic transport
are conductance quantization (in nanoconstrictions) in
steps of G0 = 2e2 /h, which have been found earlier
for quantum ballistic transport in semiconductor point
contacts17 and metal nanowires.18 However, quantization
signatures were scarcely observed20 in GNRs fabricated
with top-down methods.
Another manifestation of coherent ballistic transport
are interference phenomena, reflecting the wave nature
of the transporting physical object, and associated most
often with optical (electromagnetic waves, photons) sys-
arXiv:1502.03767v1 [hep-ph] 12 Feb 2015
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, 2015
Electromagnetic probes in heavy-ion collisions
Messengers from the hot and dense phase
H. van Hees1,2 , a , J. Weil2 , b , S. Endres2 , c , and M. Bleicher2 , d
1
Johann Wolfgang Goethe University Frankfurt, Institute for Theoretical Physics, Max-von-Laue-Str. 1,
60438 Frankfurt, Germany
2
Frankfurt Institute of Advanced Studies, Ruth-Moufang-Str. 1, 60438 Frankfurt, Germany
Abstract. Due to their penetrating nature, electromagnetic probes, i.e., lepton-antilepton
pairs (dileptons) and photons are unique tools to gain insight into the nature of the hot and
dense medium of strongly-interacting particles created in relativistic heavy-ion collisions,
including hints to the nature of the restoration of chiral symmetry of QCD. Of particular
interest are the spectral properties of the electromagnetic current-correlation function of
these particles within the dense and/or hot medium. The related theoretical investigations
of the in-medium properties of the involved particles in both the partonic and hadronic
part of the QCD phase diagram underline the importance of a proper understanding of
the properties of various hadron resonances in the medium.
1 Introduction
The transverse-momentum and invariant-mass spectra of the so-called electromagnetic probes, i.e.,
dileptons (e+ e− or µ+ µ− pairs) and photons have been identified as interesting observables early on
[1]. Since they do not participate in the strong interaction, they leave the hot and dense fireball created
in ultrarelativistic heavy-ion collisions nearly undisturbed by final-state interactions and thus provide
a direct insight into the spectral properties of the electromagnetic current-current correlation function
in the medium during the entire evolution of the collision. For theory this is also some challenge since
an accurate description of the invariant-mass spectra of dileptons and transverse-momentum spectra
of both dileptons and photons is needed, including as comprehensive a set of sources as possible,
reaching from the radiation from the very early stage of the collision (Drell-Yan processes) over
the emission from a hot and dense partonic medium (Quark-Gluon Plasma, QGP) undergoing the
transition to a hot and dense hadron-resonance gas (which is close to the chemical freeze-out of the
medium), to the finally decoupled hadronic state at thermal freeze-out.
In this paper we summarize the current status of our understanding of both the spectral properties
of the electromagnetic current-correlation function, implying some insights about the nature of chiralsymmetry restoration, and the description of the evolution of the hot and dense partonic and hadronic
fireball.
a e-mail:
b e-mail:
c e-mail:
d e-mail:
[email protected]
[email protected]
[email protected]
[email protected]
arXiv:1502.03734v1 [hep-ph] 12 Feb 2015
APCTP-PRE2015-003
IPMU15-0015
Accessing the core of naturalness, nearly degenerate
higgsinos, at the LHC
Chengcheng Hana , Doyoun Kima , Shoaib Munira and Myeonghun Parka,b,c
a
Asia Pacific Center for Theoretical Physics, San 31, Hyoja-dong,
Nam-gu, Pohang 790-784, Republic of Korea.
b
c
Department of Physics, Postech, Pohang 790-784, Korea
Kavli IPMU (WPI), The University of Tokyo, Kashiwa, Chiba 277-8583, Japan
[email protected],[email protected],
[email protected],[email protected]
Abstract
The presence of two light higgsinos nearly degenerate in mass is one of the important characteristics of suspersymmetric models meeting the naturalness criteria. Probing such higgsinos
at the LHC is very challenging, in particular when the mass-splitting between them is less than
5 GeV. In this study, we analyze such a degenerate higgsino scenario by exploiting the high
collinearity between the two muons which originate from the decay of the heavier higgsino into
the lighter one and which are accompanied by a high-pT QCD jet. Using our method, we can
achieve a statistical significance ∼ 2.9 σ as well as a S/B ∼ 17% with an integrated luminosity
of 3000 fb−1 at the 14 TeV LHC, for the pair production of higgsinos with masses 124 GeV and
120 GeV. A good sensitivity can be achieved even for a smaller mass-splitting when the higgsinos
are lighter.
1
February 13, 2015
1:25
World Scientific Review Volume - 9.75in x 6.5in
arXiv:1502.03730v1 [hep-ph] 12 Feb 2015
Chapter 1
Parton energy loss and momentum broadening at NLO in high
temperature QCD plasmas
Jacopo Ghiglieri
Institute for Theoretical Physics, Albert Einstein Center,
University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
[email protected]
Derek Teaney
Department of Physics and Astronomy, Stony Brook University,
Stony Brook, New York 11794-3800, United States
[email protected]
We present an overview of a perturbative-kinetic approach to jet propagation, energy loss, and momentum broadening in a high temperature quark-gluon plasma.
The leading-order kinetic equations describe the interactions between energetic
jet-particles and a non-abelian plasma, consisting of on-shell thermal excitations
and soft gluonic fields. These interactions include 2 ↔ 2 scatterings, collinear
bremsstrahlung, and drag and momentum diffusion. We show how the contribution from the soft gluonic fields can be factorized into a set of Wilson line
correlators on the light cone. We review recent field-theoretical developments,
rooted in the causal properties of these correlators, which simplify the calculation
of the appropriate Wilson lines in thermal field theory. With these simplifications
lattice measurements of transverse momentum broadening have become possible,
and the kinetic equations describing parton transport have been extended to
next-to-leading order in the coupling g.
1. Introduction
The suppression of highly energetic jets (or jet quenching) is one of the most striking
findings of the experimental program of heavy-ion collisions.1–5 A comprehensive
review6 can be found in this volume, which also contains another contribution
reviewing a specific approach in greater detail.7
In this review, we concentrate on a weakly-coupled kinetic approach describing the propagation of high momentum jet-like particles through a Quark-Gluon
Pasma (QGP). A detailed perturbative description of the QGP and jet-quenching
is available when the temperature is high T ΛQCD , and the momentum of the
jet-particles is much larger than the temperature, p T .
1
eloss
TU-991, IPMU15-0016
Gravitational waves from unstable domain walls in the
Standard Model Higgs potential
arXiv:1502.03725v1 [hep-ph] 12 Feb 2015
Naoya Kitajima a∗ , Fuminobu Takahashi a,b†
a
b
Department of Physics, Tohoku University, Sendai 980-8578, Japan
Kavli IPMU, TODIAS, University of Tokyo, Kashiwa 277-8583, Japan
Abstract
The effective potential for the Standard Model Higgs field allows two quasi-degenerate vacua;
one is our vacuum at the electroweak scale, while the other is at a much higher scale. The latter
minimum may be at a scale much smaller than the Planck scale, if the potential is lifted by new
physics. This gives rise to a possibility of domain wall formation after inflation. If the highscale minimum is a local minimum, domain walls are unstable and disappear through violent
annihilation processes, producing a significant amount of gravitational waves. We estimate the
amount of gravitational waves produced from unstable domain walls in the Higgs potential and
discuss detectability with future experiments.
∗
†
email:[email protected]
email: [email protected]
1
MITP/15-009
When the expansion of finite-size corrections to hydrogen Lamb shift in moments of charge
distribution breaks down
Franziska Hagelstein and Vladimir Pascalutsa
arXiv:1502.03721v1 [hep-ph] 12 Feb 2015
Institut f¨ur Kernphysik, Cluster of Excellence PRISMA,
Johannes Gutenberg-Universit¨at Mainz, D-55128 Mainz, Germany
(Dated: February 13, 2015)
We point out a limitation of the standard way of accounting the finite-size effects, i.e., when the leading
[(Zα)4 ] and subleading [(Zα)5 ] contributions to the Lamb shift are given by the mean-square radius and the
third Zemach moment of the charge distribution. This limitation may have profound consequences for the
interpretation of the “proton size puzzle”. We find, for instance, that the de R´ujula toy model of the proton
form factor does not resolve the puzzle as claimed, despite the large value of the third Zemach moment. Given
the formula which does not rely on the radii expansion, we show how tiny (less than a hundredth of percent)
changes in the proton electric form factor at a MeV scale would be able to explain the puzzle.
I.
INTRODUCTION
The proton structure is long-known to affect the hydrogen
spectrum, predominantly by an upward shift of the S-levels
expressed in terms of the root-mean-square (rms) radius,
ˆ
p
N
2
(1)
RE = hr iE , hr iE ≡ d~r rNρE (~r),
of the proton charge distribution ρE . At leading order (LO) in
the fine-structure constant α, the nth S-level is shifted by (cf.,
[1]):
∆EnS (LO) =
2(Zα)4 m3r 2
RE ,
3n3
(2)
where Z = 1 for the proton, mr is the reduced mass. The
proton charge radius has thus been extracted from the hydrogen (eH) and muonic-hydrogen (µH) Lamb shifts, with rather
contradictory results:
REp (eH) = 0.8775(51) fm [2],
REp (µH) = 0.84087(39) fm [3, 4].
(3)
(4)
The eH value is backed up by the extractions from electronproton (ep) scattering [5, 6], albeit with a notable exception [7].
The next-to-leading order (NLO) effect of the nuclear
charge distribution is given by [8]:
∆EnS (NLO) = −
with RE(2) =
(Zα)5 m4r 3
RE(2) ,
3n3
(5)
p
3
hr3 iE(2)
hr3 iE(2) the Friar radius and
ˆ
ˆ
= d~r ρE (~r ) d~r 0 |~r − ~r 0 |3 ρE (~r 0 )
(6)
the third Zemach moment. Other α5 effects of proton structure, such as polarizabilities, play a lesser role in both normal
and muonic hydrogen, and are not of relevance to our discussion of finite-size effects here.
A Lorentz-invariant definition of the above moments is
given in terms of the electric form factor (FF), GE (Q2 ), as:
d
hr2 iE = −6 lim
GE (Q2 ),
(7a)
2
Q →0 dQ2
ˆ ∞
48
dQ hr3 iE =
GE (Q2 ) − 1 + 16 hr2 iE Q2 , (7b)
4
π 0 Q
ˆ ∞
48
dQ 2 2
3
hr iE(2) =
GE (Q ) − 1 + 13 hr2 iE Q2 . (7c)
π 0 Q4
At the current level of precision, the eH Lamb shift sees
only the LO term, while in µH the NLO term becomes appreciable. An immediate resolution of the eH vs. µH discrepancy
(aka, the proton size puzzle) was suggested by de R´ujula [9],
whose toy model for proton charge distribution yielded a large
Friar radius, capable of providing the observed µH Lamb shift
using the RE value from eH. Later this model was shown to
be incompatible with the empirical FF GE extracted from ep
scattering [10, 11]. In this work we find that the µH Lamb
shift in de R´ujula’s model is not described correctly by the
standard formulae of Eqs. (2) and (5). The correct result involves an infinite series of moments, and it does not provide
any significant reduction of the discrepancy in that model. We
shall consider a different scenario of mending the discrepancy
by a small change in the proton FF, using the corrected formulae.
II.
LAMB SHIFT: TO EXPAND OR NOT
Our main observation is that the standard expansion in the
moments is only valid provided the convergence radius of the
Taylor expansion of GE in Q2 is much larger than the inverse Bohr radius of the given hydrogen-like system. In other
words, for Q2 ∼ (Zαmr )2 , the electric FF must be representable by a quickly convergent power series.
To see this we write the electric FF correction to the Coulomb
potential (−Zα/r) as follows:
ˆ
Zα ∞ dt −r√t
VFF (r) =
e
Im GE (t),
(8)
πr t0 t
where Im GE is the discontinuity in the FF across the branch
cuts in the time-like region. This potential is derived by taking
Axions in gravity with torsion
Oscar Castillo-Felisola, Crist´
obal Corral, Sergey Kovalenko, and Iv´an Schmidt
Departamento de F´ısica, Universidad T´ecnica Federico Santa Mar´ıa,
Casilla 110-V, Valpara´ıso, Chile, and
Centro Cient´ıfico Tecnol´
ogico de Valpara´ıso,
Casilla 110-V, Valpara´ıso, Chile.
arXiv:1502.03694v1 [hep-ph] 12 Feb 2015
Valery E. Lyubovitskij
Institut f¨
ur Theoretische Physik, Universit¨
at T¨
ubingen, Kepler Center for Astro and Particle Physics,
Auf der Morgenstelle 14, D-72076 T¨
ubingen, Germany,
Department of Physics, Tomsk State University, 634050 Tomsk, Russia, and
Mathematical Physics Department, Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk, Russia.
We study a scenario allowing a solution of the strong CP-problem via the Peccei–Quinn mechanism, implemented in gravity with torsion. In this framework there appears a torsion-related
pseudoscalar field known as Kalb–Ramond axion. We compare it with the so called BarberoImmirzi axion recently proposed in the literature also in the context of the gravity with torsion.
We show that they are equivalent from the view point of the effective theory. The phenomenology
of these torsion-descended axions is completely determined by the Planck scale without any additional model parameters. These axions are very light and very weakly interacting with ordinary
matter. We briefly comment on their astrophysical and cosmological implications in view of the
recent BICEP2 and Planck data.
I.
INTRODUCTION
The recent discovery of the Higgs boson at the LHC has
completed the list of the known particles, providing the
last missing element necessary for the Standard Model
(SM) to be the framework for particle physics. However,
it is well-known that the SM suffers from various internal problems indicating that this is not a fundamental
theory, and in fact it should be considered just as an effective low energy theory. The strong CP-problem is one
of these problems. It emerges from adding to the QCD
Lagrangian the so called θ-term
L⊃ θ
αs
Tr (G∧G) ,
2π
(1)
written in terms of the QCD gluon field strength 2-form
G. This is a renormalizable and gauge invariant term,
which violates CP and it is allowed in any generic gauge
theory in four dimensions. In the SM it contributes to
CP-odd observables such as the neutron electric dipole
moment, which is stringently constrained by experiment,
pushing the θ-parameter down to 10−10 . Since the natural value of this parameter should be of order one, this
becomes a fine tuning problem. The question of why it
turns out to be so small is the strong CP-problem.
A solution of the strong CP-problem has been found
by Peccei and Quinn (PQ) in the periodicity of the nonperturbative QCD θ-vacuum [1] by promoting the θ parameter in Eq. (1) to be a field θ(x). Then the interaction
θ(x) Tr (G∧G) generates in the θ-vacuum a non-trivial
potential for θ(x), selecting a zero vacuum expectation
value hθi = 0. The fluctuations around this vacuum
represent a pseudoscalar field a(x), dubbed the “axion”.
Then dynamically the CP-violating term (1) is replaced
by the CP-conserving interaction a(x) Tr (G∧G).
The θ-parameter can be promoted to be a field, by
means of a pseudoscalar field, φ(x), of any origin, coupled to the Pontryagin density Tr (G∧G) of the gluon
field. This could be a Goldstone boson of a U (1)A symmetry, spontaneously broken at some scale much larger
than the electroweak scale of 250 GeV, to be compatible
with the experimental data as well as with astrophysics
and cosmology. There are many symmetry based proposals of this kind in the literature, as possible solutions of
the strong CP-problem (for a recent review see Ref. [2]).
A characteristic feature of this approach is that all the
couplings of the axion are determined by the scale of
symmetry breaking, which is a free parameter.
On the other hand it is well-known that various scenarios for the Planckian physics involve axion-like fields
[3–6]. Those fields can play the same role as the conventional Goldstone type axions in the solution of the strong
CP-problem, but with all their couplings completely determined by the Planck scale.
In particular the axion-like fields may appear rather
naturally in a field theory on the torsionful manifolds
with its metric sector treated as a “rigid” background.
The first scenario of this kind was proposed in Ref. [7],
where an axion-like field appears as a consequence of the
constraint imposed on the quantum theory requiring the
conservation of the torsion charge, as suggested by the
classical theory.
Recently, in Ref. [8], the axion has been introduced as
a pseudoscalar field, the so called Barbero–Immirzi (BI)
axion, interacting with gravity via the Nieh–Yan density [9, 10]. One of the motivations for the introduction
of this field was the possibility of eliminating the confusing divergence present in the U (1)A rotated fermion
measure of the Euclidean path integral on the manifolds
with torsion. In addition to the usual Pontryagin density,
CERN-PH-TH-2015-029
The Supersymmetric Standard Models with a Pseudo-Dirac Gluino from Hybrid F −
and D−Term Supersymmetry Breakings
Ran Ding,1 Tianjun Li,2, 3 Florian Staub,4 Chi Tian,3 and Bin Zhu2, 5
1
Center for High-Energy Physics, Peking University, Beijing, 100871, P. R. China
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
3
School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China
4
Theory Division, CERN 1211 Geneva 23, Switzerland
5
Institute of Physics Chinese Academy of sciences, Beijing 100190, P. R. China
arXiv:1502.03614v1 [hep-ph] 12 Feb 2015
2
We propose the Supersymmetric Standard Models (SSMs) with a pseudo-Dirac gluino from hybrid
F − and D−term supersymmetry (SUSY) breakings. Similar to the SSMs before the LHC, all the
supersymmetric particles in the Minimal SSM (MSSM) obtain the SUSY breaking soft terms from
the traditional gravity mediation and have masses within about 1 TeV except gluino. To evade the
LHC SUSY search constraints, the gluino also has a heavy Dirac mass above 3 TeV from D−term
SUSY breaking. Interestingly, such a heavy Dirac gluino mass will not induce the electroweak finetuning problem. We realize such SUSY breakings via an anomalous U (1)X gauge symmetry inspired
from string models. To maintain the gauge coupling unification and increase the Higgs boson mass,
we introduce extra vector-like particles. We study the viable parameter space which satisfies all the
current experimental constraints, and present a concrete benchmark point. This kind of models not
only preserves the merits of pre-LHC SSMs such as naturalness, dark matter, etc, but also solves
the possible problems in the SSMs with Dirac gauginos due to the F -term gravity mediation.
Introduction—It is well-known that the weak scale
supersymmetry (SUSY) is the most promising extension
for physics beyond the Standard Model (SM) [1]. It provides a well-motivated and complete framework to understand the basic questions of TeV-scale physics: the
gauge hierarchy problem is solved naturally, the lightest supersymmetric particle (LSP) such as neutralino can
be a dark matter candidate, and gauge coupling unification can be realized, etc. The gauge coupling unification
strongly suggests the Grand Unified Theories (GUTs),
and only the superstring theory may describe the real
world. Thus, the supersymmetric SM (SSM) is also a
bridge between the low energy phenomenology and highenergy fundamental physics.
However, the discovered SM-like Higgs boson with a
mass around 125 GeV [2, 3] is a little bit too heavy in the
Minimal SSM (MSSM) since it requires the multi-TeV
top squarks with small mixing or TeV-scale top squarks
with large mixing [4]. Also, there exist strong constraints
on the SSMs from the LHC SUSY searches. For example,
the gluino mass mg˜ and first two-generation squark mass
mq˜ should be heavier than about 1.7 TeV if they are
roughly degenerate mq˜ ∼ mg˜ , and the squark mass mq˜ is
heavier than about 850 GeV for mg˜ mq˜ [5]. Therefore,
the naturalness of the SSMs is challenged.
The basic idea to lift Higgs mass without threatening the hierarchy problem is the introduction of additional tree-level contributions [6–12]. To escape the LHC
SUSY search constraints, there are quite a few proposals: natural SUSY [13, 14], compressed SUSY [15–17],
stealth SUSY [18], heavy LSP SUSY [19], R-parity violation [20, 21], supersoft SUSY [22–31], etc. Here, we
would like to point out that all the sparticles in the SSMs
can be within about 1 TeV as long as the gluino is heavier
than 3 TeV, which is obviously an simple modification to
the SSMs before the LHC. Also, such a heavy gluino will
not induce the electroweak fine-tuning problem if it is
(pseudo-)Dirac like the supersoft SUSY. However, there
exists some problems for supersoft SUSY with Dirac
gauginos: µ problem can not be solved via the GiudiceMasiero (GM) mechanism [32], the D-term contribution
to the Higgs quartic coupling vanishes, the right-handed
slepton may be the LSP, and the scalar components of
the adjoint chiral superfields might be tachyonic and then
break the SM gauge symmetry, etc [22]. The first three
problems can be solved in the F −term gravity mediation, while the last problem was solved recently [31].
Therefore, we will propose the SSMs with a pseudo-Dirac
gluino from hybrid F − and D−term SUSY breakings. To
be concrete, all the sparticles in the MSSM obtain SUSY
breaking soft terms from the traditional gravity mediation, and only gluino receives extra Dirac mass from the
D−term SUSY breaking. Especially, all the MSSM sparticles except gluino can be within about 1 TeV as the preLHC SSMs. The merits of this proposal are: keeping the
good properties of pre-LHC SSMs (naturalness, as well
as explanations for the dark matter and muon anomalous
magnetic moment, etc), evading the LHC SUSY search
constraints, and solving the problems in supersoft SUSY
via F -term gravity mediation. We show that such SUSY
breakings can be realized by an anomalous U (1)X gauge
symmetry inspired from string models. To achieve the
gauge coupling unification and increase the Higgs boson
mass, we will introduce vector-like particles. We shall
discuss the low energy phenomenology, and the detailed
studies will be given elsewhere [33].
Mean transverse momenta correlations in hadron-hadron
collisions in MC toy model with repulsing strings
arXiv:1502.03608v1 [hep-ph] 12 Feb 2015
Igor Altsybeev
St. Petersburg State University
Abstract. In the present work, Monte-Carlo toy model with repulsing quark-gluon strings in hadron-hadron collisions is
described. String repulsion creates transverse boosts for the string decay products, giving modifications of observables. As an
example, long-range correlations between mean transverse momenta of particles in two observation windows are studied in
MC toy simulation of the heavy-ion collisions.
Keywords: quark-gluon strings interaction, long-range correlations, Monte Carlo model
PACS: 25.75.Gz, 25.75.Ld
INTRODUCTION
Interactions between quark-gluon strings in hadron-hadron collisions are the topic of interest for many years. The
models of such interactions, however, are mostly phenomenological. For instance, the string fusion model was
proposed in [1, 2, 3]. It was shown that the string fusion phenomenon should lead to modifications of event multiplicity,
transverse momentum spectrum, and to other consequences. The string fusion scenario was implemented in a number
of MC models of hadron-hadron collisions [4, 5].
In [6], an attraction and a repulsion of chromoelectric tubes in hadron-hadron collisions is discussed. It is shown,
that such interactions should lead to azimuthal asymmetry in the distribution of secondary particles. The following
picture is considered:
1. quark-gluon tubes (strings) have a finite radius.
2. depending on the transverse distance between them, strings may overlap and interact.
3. strings attract or repel each other in the transverse direction.
In the first part of this proceeding, the toy MC model based on ideas from [6] is described. The motivation for
development of such a model comes, for instance, from the results of dihadron correlations measured in Au-Au
collisions in STAR [7], where patterns of the collective behavior are observed and a detailed fit of the correlation
structures was developed. It is interesting to see what would be the "collectivity" in the frame of the toy MC model with
repulsion strings. In the second part of the current proceeding, the so-called mean transverse momentum correlations
are extracted from the toy model events. This observable may be useful to disentangle between string interaction
scenarios, for example, between the string repulsion and the string fusion. Dihadron analysis of the MC toy model
data is presented in the same proceedings [9].
MONTE-CARLO TOY MODEL
In this section a Monte-Carlo (MC) toy model with repulsing strings is described. The MC model is applicable to
different types of hadron-hadron collisions (pp, AA, pA, etc.).
Stage 1. Simulation of hadron-hadron collisions, strings formation.
In this MC model, initial positions of the nucleons in nuclei are generated in accordance to Woods-Saxon distribution
(for the Pb208 , the WS radius is 6.62 fm and parameter a = 0.546 fm). Nucleon core effect is not taken into account
to speed-up computations. Inside each nucleon, some number of partons is distributed in transverse (xy) plane with
2D-Gauss law, with σxy = 0.4 fm. The mean number of partons npartons inside nucleons is dependent on a collision
energy and is a model parameter. Interaction between colliding hadrons is implemented at the partonic level: partons
arXiv:1502.03582v1 [hep-ph] 12 Feb 2015
KUNS-2544, EPHOU-15-003,WU-HEP-15-03
D-brane instanton induced µ-terms and
their hierarchical structure
Hiroyuki Abe1, Tatsuo Kobayashi2, Yoshiyuki Tatsuta1,
and Shohei Uemura3
1
2
Department of Physics, Waseda University, Tokyo 169-8555, Japan
Department of Physics, Hokkaido University, Sapporo, 060-0810 Japan
3
Department of Physics, Kyoto University, Kyoto 606-8502, Japan
Abstract
We study the µ-term matrix of Higgs pairs induced by the D-brane instanton effects
in intersecting D6-brane models compactified on T 6 . It is found that the µ-term
matrix has a certain permutation symmetry and its eigenvalues have large hierarchical
structure without fine tuning.
ICRR-Report-698-2014-24
arXiv:1502.03550v1 [hep-ph] 12 Feb 2015
IPMU 15-0017
Affleck-Dine baryogenesis after D-term inflation
and solutions to the baryon-DM coincidence problem
Masahiro Kawasakia,b and Masaki Yamadaa,b
a
Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha,
Kashiwa, Chiba 277-8582, Japan
b
Kavli IPMU (WPI), TODIAS, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa,
277-8583, Japan
Abstract
We investigate the Affleck-Dine baryogenesis after D-term inflation with a positive
Hubble-induced mass term for a B − L flat direction. It stays at a large field value
during D-term inflation, and just after inflation ends it starts to oscillate around the
origin of the potential due to the positive Hubble-induced mass term. The phase
direction is kicked by higher-dimensional K¨
ahler potentials to generate the B − L
asymmetry. The scenario predicts nonzero baryonic isocurvature perturbations, which
would be detected by future observations of CMB fluctuations. We also provide a
D-term inflation model which naturally explain the coincidence of the energy density
of baryon and dark matter.
Unstable Particles near Threshold
Dongjin Chway,1, ∗ Tae Hyun Jung,1, † and Hyung Do Kim1, 2, ‡
1
Department of Physics and Astronomy and Center for Theoretical Physics,
Seoul National University, Seoul 151-747, Korea
2
Institute for Advanced Study, Princeton, NJ08540, USA
arXiv:1502.03541v1 [hep-ph] 12 Feb 2015
We explore physics of unstable particles when mother particle mass is around the sum of its
daughter particle masses. In this case, the conventional wave function renormalization factor is
ill-defined. We propose a simple resolution of the threshold singularity problem which still allows
the use of narrow width approximation by defining branching ratio in terms of spectral density. The
resonance peak and shape is different for different decay channels and no single decay width can be
assigned to the unstable particles. Non-exponential decay happens in all time scales.
Introduction The narrow width approximation (NWA)
has played an important role in studying unstable particles. Unstable particle states can not be asymptotic
states of a scattering amplitude in order to keep unitarity and causality[1]. Nevertheless, NWA allows similar
treatments of unstable particles by factorizing full scattering cross sections of stable states into production and
decay parts. In most practical situations, heavy off-shell
calculations are immensely simplified with NWA.
When NWA is used for Standard Model calculations
with realistic parameters, it is enough to take conventional wave function renormalization factor, Z for unstable particles, whose inverse is defined by a real part
of G−1 differentiated by momentum square at physical
mass square. Conventional choice of the physical mass is
a zero of Re(G−1 ). They work when all the dressed propagators [2] are well approximated by Breit-Wigner(BW)
distribution [3].
However, this Z is ill-defined in some examples beyond the Standard Model. In many cases, a self energy included
in a dressed propagator is proportional
q
2
2
b)
b)
)(1 − (ma −m
) where ma,b are
to β¯ ≡ (1 − (ma +m
2
2
p
p
masses of particles propagating in the loop. This is because the phase space volume of decay is proportional
to β¯ and self energy and decay rate are closely related
by the optical theorem. The classification of interactions
providing the self energy with the same property is done
later in this Letter. For simplicity, we discuss the problem with a scalar theory in the text.
¯ the Z −1 contains
For the self energy proportional to β,
a term proportional to 1/β¯ which diverges as the physical
mass approaches the threshold mass, ma +mb from below.
Taken faithfully, Z → 0 means every production and
decay of the unstable particle vanish and the particle
becomes isolated from the theory no matter how strong
the interaction is, which is nonsense.
Solving the ill-defined Z problem has been attempted
mostly by using complex pole scheme[4, 5] which relates
complex pole(s) on the second Riemann sheet to physical quantities: its real part to physical mass, imaginary
part to decay rate, and residue to Z. After the complex
pole was conjectured to have physical meaning [6], its
gauge independence was shown in Z boson in the Standard Model [7] and scalars [8], and the scheme was employed to Higgs physics[9]. However, using complex pole
can be traced back to residue theorem for contour integral
over lower half plane of the second Riemann sheet where,
below a threshold, the analytically continued propagator
G2 defined in the second Riemann sheet deviates from
the correct propagator G which should have been used
in exact calculation.
To understand the problem, it is important to know
what really happens to the dressed propagator as the
physical mass approaches a threshold mass. If the physical mass is near the threshold, the kinetic term can be
represented by p2 −m2 ∝ β¯2 , while the self energy term is
proportional to β¯ around the peak. Thus the self energy
is dominant near the peak and it changes the shape of the
propagater to be totally different from BW distribution.
We propose generalized narrow width approximation by
defining branching ratio in terms of spectral density.
As the propagator G changes, ρ(p2 ), the spectral
density of K¨all´en-Lehmann representation [10, 11] also
changes. Unlike BW distribution which gives exponential
decay with a rate of imaginary part
pole,
R of a complex
2 the
√
∞
survival probability, P (t) ≡ 0 dSe−i St ρ(S) does
not exponential decay. Deviation from exponential decay for very short or long time in quantum field theory is
well known [12, 13]. We show non-exponential decay pattern in middle range of time when most decay happens
if they are at the threshold.
Factorization Consider a full scattering cross section
constructed with all external states by stable particles.
For simplicity, assume that one Feynmann diagram (Fig.
1) dominantly determines the process which contains
an unstable particle state, φ that ends up being
a fiR
nal Rstate λ. After inserting the identity, dSδ(S −
p2φ ) d4 pφ δ 4 (pφ − pλ )θ(p0φ ) into the full scattering cross
section, we obtain
σ( initial → 1, 2, · · · , n, λ)
Z Smax
√
=
dS σ(initial → m1 , · · · , mn , S) ρλ (S) (1)
Smin
arXiv:1502.03463v1 [hep-ph] 11 Feb 2015
Prepared for submission to JCAP
Decoupled Sectors and Wolf-Rayet
Galaxies
Willy Fischler1 , Jimmy2 and Dustin Lorshbough1
1
Department of Physics and Texas Cosmology Center
The University of Texas at Austin, TX 78712.
2
Department of Physics and Astronomy
Texas A&M University, College Station, TX 77843.
E-mail: [email protected], [email protected],
[email protected]
Abstract. The universe may contain several decoupled matter sectors which primarily
couple through gravity to the Standard Model degrees of freedom. We focus here on
the description of astrophysical environments that allow for comparable densities and
spatial distributions of visible matter and decoupled dark matter. We discuss four
Wolf-Rayet galaxies (NGC 1614, NGC 3367, NGC 4216 and NGC 5430) which should
contain comparable amounts of decoupled dark and visible matter in the star forming
regions. This could lead to the observation of Gamma Ray Burst events with physics
modified by jets of dark matter radiation.
Flavor dependence of baryon melting temperature
in effective models of QCD
Juan M. Torres-Rincon, Benjamin Sintes and Joerg Aichelin
arXiv:1502.03459v1 [hep-ph] 11 Feb 2015
Subatech, UMR 6457, IN2P3/CNRS, Universit´e de Nantes,
´
Ecole
de Mines de Nantes, 4 rue Alfred Kastler 44307, Nantes, France
We apply the three-flavor (Polyakov–)Nambu–Jona-Lasinio model to generate baryons as quarkdiquark bound states using many-body techniques at finite temperature. All the baryonic states
belonging to the octet and decuplet flavor representations are generated in the isospin-symmetric
case. For each state we extract the melting temperature at which the baryon may decay into a
quark-diquark pair. We seek for an evidence of the strangeness dependence of the baryon melting
temperature as suggested by the statistical thermal models and supported by lattice-QCD results.
A clear and robust signal for this claim is found, pointing to a flavor dependence of the hadronic
deconfinement temperature.
I.
INTRODUCTION
Experiments at the relativistic heavy-ion collider and
the large hadron collider (LHC) have shown that a quarkgluon plasma (QGP) is produced during the first stages
of a relativistic heavy-ion collision. The QGP is the
phase of quantum chromodynamics (QCD) at high temperature/density where quarks and gluons are not colorconfined into hadrons. From this QGP phase, the produced fireball undergoes a transition to the hadronic
phase at a given hadronization temperature.
At nearly vanishing baryochemical potential the phase
transition to the hadronic state is known to be a
crossover [1]. Experimentally it is known that at the
so-called chemical freeze-out temperature, which at vanishing chemical potential is close to the hadronization
temperature, the hadrons are in statistical equilibrium.
This is the result of a fit of the hadron abundances in the
framework of a statistical model [2, 3]. This fit determines the chemical freeze out temperature and describes
the multiplicity of almost all nonresonant hadrons with
an astonishing precision. After chemical freeze out the
hadrons still interact but the chemical composition of the
hadron gas remains (almost) unchanged. Results from
high energetic central Pb+Pb collisions at LHC show
that the freeze-out temperatures extracted by thermal
fits [4] are close to the crossover temperature predicted
by lattice-QCD studies [5].
A natural question to ask is whether the freeze-out conditions depend on the hadron species, i.e. if the chemical freeze-out temperature depends on flavor. Thermal
fits presented in Ref. [4] show a tension when fitting the
different baryonic species with a common freeze-out temperature, suggesting that the chemical freeze-out temperature for nonstrange baryons is smaller (around 16 MeV)
than that for strange baryons [3, 4].
If this is the case, one may also suggest that the
hadronization temperature depend on the strangeness
content of the hadron. This idea was brought up quite
recently by the authors of Ref. [6]. In this reference,
the strangeness dependence of the crossover temperature
has been studied with continuum-extrapolated results of
lattice-QCD calculations. The conclusion was that the
crossover temperature (measured by the maximum of a
susceptibility ratio) is about 15 MeV larger for strange
hadrons than for those composed by light quarks. This
difference is in surprisingly good accordance with the results from statistical-thermal fits of ALICE abundances,
even if the two physical processes (hadronization and
chemical freeze-out) are conceptually distinct.
In this paper we study the flavor dependence of the
hadronization temperature by using one of the simplest
effective models for strong interactions. The Nambu–
Jona-Lasinio (NJL) model is an effective model for lowenergy QCD where the gluonic fields are integrated out
and the basic interaction consists of a 4-quark contact
vertex. Although the gluon dynamics is absent in this
model, some of the gluonic features can be reproduced
by the so-called Polyakov–Nambu–Jona-Lasinio (PNJL)
model.
This effective model lacks true confinement. However,
hadrons can be thought as dynamically generated states
from multiquark rescattering, thus providing a nonperturbative mechanism for an effective confinement. The
properties of these hadrons (masses and widths) can
be obtained by solving the Bethe–Salpeter (BS) equation (for mesons) and the Fadeev equation (for baryons)
with some approximations. Many approaches have been
applied in which meson and baryon properties at zero
temperature have been computed within the NJL/PNJL
models [7–11]. These models can be extended to finite
temperatures and densities. Such an extension allows for
calculating the “Mott temperature”, the temperature at
which hadrons are not bound anymore, because they can
melt into a quark and a diquark.
Our aim is to find the Mott temperature for several hadrons within the three-flavor NJL/PNJL models, and extract conclusions about its dependence on the
strangeness content of the hadrons. In Sec. II we introduce the NJL and PNJL Lagrangians and provide a short
remainder on how a meson can be effectively described
as a bound state of a quark-antiquark pair. In Sec. III we
use the Bethe-Salpeter equation for two quarks to generate diquarks and extract their properties as a function of
Ab-initio calculation of the photonuclear cross section of
10
B
M.K.G. Kruse,1, ∗ W.E. Ormand,1 and C.W. Johnson2
arXiv:1502.03464v1 [nucl-th] 11 Feb 2015
1
Lawrence Livermore National Laboratory, P.O. Box 808, L-414, Livermore, California 94551, USA
2
San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA
(Dated: February 13, 2015)
We present for the first-time the photonuclear cross section of 10 B calculated within the ab-initio No
Core Shell Model framework. Realistic two-nucleon (NN) chiral forces up to next-to-next-to-nextorder (N3LO), which have been softened by the similarity renormalization group method (SRG) to
λ = 2.02 fm−1 , were utilized. The electric-dipole response function is calculated using the Lanczos
method. The effects of the continuum were accounted for by including neutron escape widths derived
from R-matrix theory. The calculated cross section agrees well with experimental data in terms of
structure as well as in absolute peak height, σmax = 4.85 mb at photon energy ω = 23.61 MeV, and
integrated cross section 85.36 MeV· mb. We test the Brink hypothesis by calculating the electricdipole response for the first five positive-parity states in 10 B and verify that dipole excitations built
upon the ground- and excited states have similar characteristics.
Electric-dipole transitions are an important excitation
mode characterizing many facets of nuclear structure.
Of particular interest is their strongly collective nature,
which is manifested in what is known as the giant-dipole
resonance (GDR). The GDR is ubiquitous in nuclei, and
since its initial observation [1], much experimental and
theoretical effort has been devoted to understanding its
properties. The centroid of the GDR generally scales as
the inverse of the nuclear radius, and experimentally is
found to be ∼ 79A−1/3 MeV, while the width is of the order 5 MeV [2]. Early on, phenomenological models were
proposed by Goldhaber and Teller [3] and Steinwedel and
Jensen [4] based on proton-neutron fluids that were able
to describe the energy of the resonance. The width, on
the other hand, was postulated to be due to the GDR
damping into other nuclear modes of motion [5, 6]. A further, intriguing property is that a collective dipole mode
exists on each state of the nuclear system, as hypothesized by Brink [7]. The resonant part of the photonuclear
cross section has been calculated with semi-realistic interactions for 4 He [8, 9], 6 He and 6 Li [10, 11] and 7 Li
[12]. More recent calculations for 4 He utilizing modern
realistic two- and three-body interactions have also been
performed [13, 14]. These calculations have either used
the framework of the hyperspherical harmonics (HH) expansion [15, 16] or the No Core Shell Model (NCSM) [17–
19]. Recently the Lorentz integral method [20, 21] was
used in conjunction with coupled-cluster calculations to
calculate the 16 O giant dipole resonance [22].
In this letter, we report on a theoretical study of the
properties of the GDR for 10 B within the framework of
the ab initio No Core Shell Model (NCSM) [17–19]. We
study the convergence properties of the GDR as a function of the model space size and present the photo-nuclear
absorption cross section for 10 B. We demonstrate the influence of more complex modes on the damping of the
GDR as well as the influence of the neutron escape width
on the dipole response. Finally, we test the Brink hypothesis by calculating the dipole response on positive parity
excited states in 10 B and find a robust GDR built on each
of these states exhibiting remarkably similar properties.
The NCSM is a bound-state technique appropriate
for light nuclei that uses as input realistic two- and
three-body nuclear interactions. The NCSM determines
the eigenenergies and wave functions of the nucleus by
expressing the translationally invariant Hamiltonian in
terms of antisymmetric combinations of single-particle
harmonic oscillator (HO) states of frequency Ω. The size
of the Slater determinant basis is determined by the total HO quanta, Nmax , available in the system above the
lowest configuration. Realistic interactions that make
the link between structure and quantum chromodynamics explicit are derived using the effective field theory
(EFT) for nuclear forces [23, 24]. In this work, we include
nucleon-nucleon (NN) terms up to next-to-next-to-nextleading order (N3LO) [25]. To enhance convergence, an
effective interaction was employed using the similarity
renormalization group procedure (SRG) [26–29] with a
momentum-decoupling value of λ = 2.02 fm−1 . At this
λ value, the binding energies of p-shell nuclei are reproduced as though the calculation was performed with both
the N3LO NN and N2LO NNN interactions [30–32]. In
order to isolate effects of the strong interaction, we use an
isospin-symmetric (isoscalar) interaction, and ignore the
Coulomb interaction. All calculations were performed
with ~Ω = 20 MeV.
The dipole response function S(ω) on an initial state
with angular momentum J and energy E is given by
S(ω) =
X
1
ˆ z |JM i|2 δ(Ef − E − ω)
|hJf Mf |D
2J + 1
f,M
X B(E1; J → Jf )
=
δ(Ef − E − ω),
3
(1)
f
where we assume the photon polarization is in the zdirection, the sum is taken over all initial orientations M
and final states f , and ω is the photon energy. Dµ is the
Determination of the structure of the X(3872) in pA
¯ collisions
A.B. Larionova,b , M. Strikmanc , M. Bleichera,d
arXiv:1502.03311v1 [nucl-th] 11 Feb 2015
a
Frankfurt Institute for Advanced Studies (FIAS), D-60438 Frankfurt am Main, Germany
b
National Research Centre ”Kurchatov Institute”, 123182 Moscow, Russia
c
Pennsylvania State University, University Park, PA 16802, USA
d
Institut f¨
ur Theoretische Physik, J.W. Goethe-Universit¨
at, D-60438 Frankfurt am Main, Germany
Abstract
Currently, the structure of the X(3872) meson is unknown. Different competing models
of the c¯
c exotic state X(3872) exist, including the possibilities that this state is either
¯ ∗0 + c.c. composition, a c¯
a mesonic molecule with dominating D 0 D
cq q¯ tetraquark, or a
c¯
c-gluon hybrid state. It is expected that the X(3872) state is rather strongly coupled to
the p¯p channel and, therefore, can be produced in p¯p and p¯A collisions at PANDA. We
¯∗
propose to test the hypothetical molecular structure of X(3872) by studying the D or D
stripping reactions on a nuclear residue.
Keywords:
X(3872), p¯A reactions, charmed meson production
PACS: 25.43.+t, 14.40.Rt, 14.40.Lb, 24.10.Ht
1. Introduction
The discovery of exotic c¯
c mesons at B-factories and at the Tevatron stimulated interest
to explore the possible existence of tetraquark and molecular meson states. The famous
X(3872) state has been originally found by BELLE [1] as a peak in π + π − J/ψ invariant
mass spectrum from exclusive B ± → K ± π + π − J/ψ decays. Nowadays the existence of the
X(3872) state and its quantum numbers J P C = 1++ are well established [2]. In particular,
radiative decays X(3872) → J/ψγ, X(3872) → ψ ′ (2S)γ [3] point to the positive C-parity
of the X(3872). Probably the most intriguing feature is that the mass of the X(3872)
is within 1 MeV the sum of the D 0 and D ∗0 meson masses. This prompted the popular
¯ ∗ + DD
¯ ∗ molecule. Other exotic X,Y,Z states, such
conception of the X(3872) being a D D
as the X(3940) [4], Y (4140) [5], X(4160) [6] (c.f. recent reviews [7, 8] for a more complete
¯ ∗ or D ∗ D
¯∗
list), may be interpreted as molecular states of D ∗ D
S S.
To probe the molecular nature of the X(3872) structure has been difficult. So far,
most theoretical calculations have been focused on the description of radiative and isospinviolating decays of the X(3872). For example, the X(3872) → J/ψγ decay can be well
Email addresses: [email protected] (A.B. Larionov), [email protected]
(M. Strikman), [email protected] (M. Bleicher)
Preprint submitted to Elsevier
February 12, 2015
Spectrometer for new gravitational experiment with UCN
G.V. Kulin1, A.I. Frank1, S.V. Goryunov1, D.V. Kustov1,3, P. Geltenbort2,
M. Jentschel2, A.N. Strepetov4, V.A. Bushuev5
1
Joint Institute for Nuclear Research, Dubna, Russia
Institut Lauer-Langevin, Grenoble, France
3
Institute for Nuclear Research, Kiev, Ukraine
4
Institute of General and Nuclear Physics, RCC «Kurchatov Institute», Moscow, Russia
5
Moscow State University, Moscow, Russia
2
Abstract
We describe an experimental installation for a new test of the weak
equivalence principle for neutron. The device is a sensitive gravitational
spectrometer for ultracold neutrons allowing to precisely compare the gain in
kinetic energy of free falling neutrons to quanta of energy  transferred to
the neutron via a non stationary device, i.e. a quantum modulator.
The results of first test experiments indicate a collection rate allowing
measurements of the factor of equivalence  with a statistical uncertainty in
the order of 5×10-3 per day. A number of systematic effects were found, which
partially can be easily corrected. For the elimination of others more detailed
investigations and analysis are needed. Some possibilities to improve the
device are also discussed.
1. Introduction.
Apparently, neutrons are the most suitable objects to investigate the gravity interaction
of elementary particles. Although gravitational experiments with neutrons have a more than
half a century history [1], the existing experimental data are quite scanty, and their accuracy is
many orders of magnitude inferior to the accuracy of gravitational experiments with
macroscopic bodies and atomic interferometers [2-6].
Almost fifteen years after the first observation of the neutron fall in the Earth’s
gravitational field [1], the gravitational acceleration was measured in a classical experiment
with an accuracy of about 0.5% [7]. However, the fact of gravitational acceleration of the
neutron was already earlier considered as obvious and used for precise measurements of the
coherent scattering length of neutrons by nuclei. In the Maier-Leibnitz–Koester gravitational
refractometer [8,9], the initially horizontal neutron beam moved parabolically, fell from height
h on a liquid mirror, reflected from it, and arrived at a detector. Varying the incidence height,
1
arXiv:1502.03174v1 [physics.ins-det] 11 Feb 2015
Low Background Signal Readout Electronics for the
Majorana Demonstrator
I. Guinn1 , N. Abgrall2 , F. T. Avignone III3,4 , A. S. Barabash5 ,
F. E. Bertrand4 , V. Brudanin6 , M. Busch7,8 , M. Buuck1 , D. Byram9 ,
A.S. Caldwell10 , Y-D. Chan2 , C. D. Christofferson10 , C. Cuesta1 ,
J. A. Detwiler1 , Yu. Efremenko11 , H. Ejiri12 , S. R. Elliott13 ,
A. Galindo-Uribarri4 , G. K. Giovanetti14,8 , J. Goett13 , M. P. Green4 ,
J. Gruszko1 , V. E. Guiseppe3 , R. Henning14,8 , E. W. Hoppe15 ,
S. Howard10 , M. A. Howe14,8 , B. R. Jasinski9 , K. J. Keeter16 ,
M. F. Kidd17 , S. I. Konovalov5 , R. T. Kouzes15 , B. D. LaFerriere15 ,
J. Leon1 , J. MacMullin14,8 , R. D. Martin9 , S. J. Meijer14,8 ,
S. Mertens2 , J. L. Orrell15 , C. O’Shaughnessy14,8 , N. R. Overman15 ,
A. W. P. Poon2 , D. C. Radford4 , J. Rager14,8 , K. Rielage13 ,
R. G. H. Robertson1 , E. Romero-Romero11,4 , M. C. Ronquest13 ,
B. Shanks14,8 , M. Shirchenko6 , N. Snyder9 , A. M. Suriano10 ,
D. Tedeschi3 , J. E. Trimble14,8 , R. L. Varner4 , S. Vasilyev6 , K. Vetter2
18 , K. Vorren14,8 , B. R. White4 , J. F. Wilkerson14,8,4 , C. Wiseman3 ,
W. Xu13 , E. Yakushev6 , C-H. Yu4 , and V. Yumatov5
The Majorana Collaboration
1
Center for Experimental Nuclear Physics and Astrophysics and
Department of Physics, University of Washington, Seattle, WA, USA
2
Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
3
Department of Physics and Astronomy, University of South Carolina, Columbia, SC, USA
4
Oak Ridge National Laboratory, Oak Ridge, TN, USA
5
Institute for Theoretical and Experimental Physics, Moscow, Russia
6
Joint Institute for Nuclear Research, Dubna, Russia
7
Department of Physics, Duke University, Durham, NC, USA
8
Triangle Universities Nuclear Laboratory, Durham, NC, USA
9
Department of Physics, University of South Dakota, Vermillion, SD, USA
10
South Dakota School of Mines and Technology, Rapid City, SD, USA
11
Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA
12
Research Center for Nuclear Physics and Department of Physics, Osaka University, Ibaraki,
Osaka, Japan
13
Los Alamos National Laboratory, Los Alamos, NM, USA
14
Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC, USA
15
Pacific Northwest National Laboratory, Richland, WA, USA
16
Department of Physics, Black Hills State University, Spearfish, SD, USA
17
Tennessee Tech University, Cookeville, TN, USA
E-mail: [email protected]
18
Alternate Address: Department of Nuclear Engineering, University of California, Berkeley, CA, USA
Abstract. The Majorana Demonstrator is a planned 40 kg array of Germanium detectors
intended to demonstrate the feasibility of constructing a tonne-scale experiment that will seek
neutrinoless double beta decay (0νββ) in 76 Ge. Such an experiment would require backgrounds
of less than 1 count/tonne-year in the 4 keV region of interest around the 2039 keV Q-value of
the ββ decay. Designing low-noise electronics, which must be placed in close proximity to the
detectors, presents a challenge to reaching this background target. This paper will discuss the
Majorana collaboration’s solutions to some of these challenges.
1. Introduction to the Majorana Demonstrator
The Majorana Demonstrator (MJD)[1][2] is an array of p-type point contact (PPC) high
purity Germanium (HPGe) detectors intended to search for neutrinoless double beta decay (0νββ
decay) in 76 Ge. MJD will consist of 40 kg of detectors, 30 kg of which will be isotopically enriched
to 87% 76 Ge. The array will consist of 14 strings of four or five detectors placed in two separate
cryostats. One of the main goals of the experiment is to demonstrate the feasibility of building
a tonne-scale array of detectors to search for 0νββ decay with a much higher sensitivity. This
involves acheiving backgrounds in the 4 keV region of interest (ROI) around the 2039 keV Qvalue of the ββ decay of less than 1 count/ROI-t-y. Because many backgrounds will not directly
scale with detector mass, the specific background goal of MJD is less than 3 counts/ROI-t-y.
MJD uses a wide variety of background reduction techniques. The PPC geometry allows
descrimination between multi-site events, consisting mostly of Compton-scatterred gamma
backgrounds, and single-site events, which includes 0νββ decay. The array is housed in
passive shielding of copper, lead and high density polyethylene, along with an active muon veto
system. Furthermore, the experiment is located 4850 ft underground at the Sanford Underground
Research Facility (SURF), with 4260 mwe overburden to avoid cosmic rays. All materials used
inside of the shielding are made of highly radiopure materials; in particular, the copper parts are
made out of ultra-pure electroformed copper (EFCu) that is grown underground at SURF. An
extensive radio-assay campaign verifies the purity of all materials used in the experiment. This
assay data is used in a detailed model of the expected backgrounds of the Demonstrator[3].
In October 2014, the upper limit on background projected by the model was 3.1 counts in the
ROI, with the largest contributions to MJD’s backgrounds in the ROI being the cables, electrical
connectors and front end electronics inside of the cryostat. These background predictions are
expected to shrink as assay limits improve.
2. Signal Readout Electronics
The signal readout electronics chain is responsible for integrating the current pulses from the
Germanium detectors, amplifying that signal and carrying it out of the shielding and to a
digitizer. The first stage of integration is done directly above each detector by low-noise, lowmass front-end boards (LMFEs). The signal is carried by bundles of coaxial cables along the
strings of detectors and the thermosyphon crossarm to a feedthrough flange, where it is fed into
a preamplifier. Because each end of the cable bundles are not easily accessible, signal connectors
are placed above the cold plate to allow connection and disconnection of cables. Since all of these
components are inside of the cryostat, it is important to design them with radiopure materials
and with very low masses to minimize backgrounds, without compromising noise characteristics.
The components must further be robust under vacuum and thermal cycling to liquid nitrogen
temperature, and must not break when handled inside of a glove box with reduced dexterity.
Rate Analysis or a Possible Interpretation of
Abundances
Miklós Kiss1
Berze High School/Gyöngyösi Berze Nagy János Gimnázium
H-3200 Gyöngyös, Kossuth u. 33., Hungary
E-mail: [email protected]
Heavy elements are formed in nucleosynthesis processes. Abundances of these elements can be
classified as elemental abundance, isotopic abundance, and abundance of nuclei. In this work we
propose to change nucleon identification from the usual (Z,A) to (Z,N), which allows reading
out new information from the measured abundances.
We are interested in the neutron density required to reproduce the measured abundance of nuclei
assuming equilibrium processes. This is only possible when two stable nuclei are separated by
an unstable nucleus. At these places we investigated the neutron density required for equilibrium
nucleosynthesis both isotopically and isotonically at temperatures of AGB interpulse and
thermal pulse phases. We obtained an estimate for equilibrium nucleosynthesis neutron density
in most of the cases. Next we investigated the possibility of partial formation of nuclei. We
analyzed the meaning of the branching factor. We found a mathematical definition for the
unified interpretation of a branching point closed at isotonic case and open at isotopic case. We
introduce a more expressive variant of branching ratio called partial formation rate. With these
we are capable of determining the characteristic neutron density values. We found that all
experienced isotope ratios can be obtained both at 108 K temperature and at 3 ⋅ 108 K temperature
and at intermediate neutron density ( ≤ 2 ⋅ 1012 cm −3 ).
XIII Nuclei in the Cosmos
7-11 July, 2014
Debrecen, Hungary
1
Speaker
Rate Analysis or a Possible Interpretation of Abundances
Miklós Kiss
1. Introduction
Nearly sixty years after BBFH [1], it is possible and necessary to review and rethink our
knowledge about the neutron capture nucleosynthesis. The result of the formation of the nuclei
is shown in the abundances. It is important to mention that the formed unstable nuclei have
decayed into stable nuclei and we are only able to see the resulting stable nuclei.
"The success of any theory of nucleosynthesis has to be measured by comparison with the
abundance patterns observed in nature." say Käppeler, Beer and Wisshak [2], that is, we need to
create such model that gives back the observed abundance.
Because of the formation of nuclei takes place in a variety of conditions, the experienced
abundance is a result of more processes. Therefore more models are necessary for the alternate
conditions. According to the conditions of the models the nuclei are classified into categories as
s-nuclei, r-nuclei etc.
It seems that the reverse approach is also useful: the abundance is the preserver of the
nuclei’s formation conditions. So instead investigating whether the theoretical model fits the
observed abundance, we look for the circumstances when the observed abundance is available.
To do this we need suitable data: the half-life of unstable nuclei and the neutron capture
cross section of nuclei. These data are not constant always. At some nuclei the half-lives depend
on the temperature [2,3,4]. Fortunately, the reaction rate per particle pair < σv > is constant
between 10 and100 keV because of the energy dependence of σ [2,3]. So we can use the σ
values at 30 keV [5]. The possible resonances only improve the capture capabilities.
2. Nucleon identification
Change the nucleon identification from the usual (Z,A) to (Z,N). Look the abundance of
individual nuclei on chart [6] (see Fig. 1). This will allow us to read new information from the
various measured abundances.
Fig. 1. Charts with isotopic and individual abundance notation
For example 96 Zr has 2.80 percents isotopic abundance and 98 Mo has 24.13 percents.
But individual abundances are 0.32 and 0.605. So such way one can see the real ratio between
them [7].
2