Nuclear Theory·nucl-th

Tuesday·February 9, 2016

9 papers—5 primary·4 cross-listed

01
[Submitted on 6 Feb 2016]
Electromagnetic fields with electric and chiral magnetic conductivities in heavy ion collisions
Hui Li🇨🇳 · Xin-li Sheng🇨🇳 · Qun Wang🇨🇳
We derive analytic formula for electric and magnetic fields produced by a moving charged particle in a conducting medium with the electric conductivity $σ$ and the chiral magnetic conductivity $σ_{χ}$ . We use the Green function method and assume that $σ_{χ}$ is much smaller than $σ$ . The compact algebraic expressions for electric and magnetic fields without any integrals are obtained. They recover the Lienard-Wiechert formula at vanishing conductivities. Exact numerical solutions are also found for any values of $σ$ and $σ_{χ}$ and are compared to analytic results. Both numerical and analytic results agree very well for the scale of high energy heavy ion collisions. The space-time profiles of electromagnetic fields in non-central Au+Au collisions have been calculated based on these analytic formula as well as exact numerical solutions.
Comments:
RevTex 4, 7 figures, 13 pages; section III-B has been re-written using dimensionful variables to improve readability; added references and one figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.02223 [pdf]
PRC(2016)·110 citations
02
[Submitted on 8 Feb 2016]
Light-quark baryon spectroscopy within ANL-Osaka dynamical coupled-channels approach
Hiroyuki Kamano🇯🇵
Recent results on the study of light-quark baryons with the ANL-Osaka dynamical coupled-channels (DCC) approach are presented, which contain the N* and Delta* spectroscopy via the analysis of pi N and gamma N reactions and the Lambda* and Sigma* spectroscopy via the analysis of K- p reactions. A recent application of our DCC approach to neutrino-nucleon reactions in the resonance region is also presented.
Comments:
8 pages, 7 figures. Contribution to the proceedings of ECT* Workshop on Nucleon Resonances: From Photoproduction to High Photon Virtualities, Trento, Italy, October 12-16, 2015
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1602.02511 [pdf]
Few Body Syst.(2016)·4 citations
03
[Submitted on 8 Feb 2016]
Polarization observables in the $e^{+} e^{-} \to Λ ˉ Λ$ reaction
Göran Fäldt
Cross-section, vector-polarization, and tensor-polarization distributions are calculated for the reactions $e^{+} e^{-} \to p ˉ p$ and $e^{+} e^{-} \to Λ ˉ Λ$ . Each reaction requires six characteristic functions that are bilinear in the, possibly complex, electromagnetic form factors, denoted $G_{E} (P^{2})$ and $G_{M} (P^{2})$ , of $p$ and $Λ$ . For the hyperon reaction also the joint-decay distributions of $Λ$ and $Λ ˉ$ are calculated. Their knowledge allow a complete determination of the hyperon electromagnetic form factors, without measuring hyperon spins. We explain how this is done in practice. For some tensor-polarization components our results are in conflict with previously repeatedly published distributions.
Comments:
17 pages
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.02532 [pdf]
EPJA(2016)·54 citations
04
[Submitted on 8 Feb 2016]
Elastic pion-nucleon scattering in chiral perturbation theory: A fresh look
D. Siemens🇩🇪 · V. Bernard🇫🇷 · E. Epelbaum🇩🇪 · A. Gasparyan🇩🇪 · H. Krebs🇩🇪 · Ulf-G. Meißner🇩🇪
Elastic pion-nucleon scattering is analyzed in the framework of chiral perturbation theory up to fourth order within the heavy-baryon expansion and a covariant approach based on an extended on-mass-shell renormalization scheme. We discuss in detail the renormalization of the various low-energy constants and provide explicit expressions for the relevant $β$ -functions and the finite subtractions of the power-counting breaking terms within the covariant formulation. To estimate the theoretical uncertainty from the truncation of the chiral expansion, we employ an approach which has been successfully applied in the most recent analysis of the nuclear forces. This allows us to reliably extract the relevant low-energy constants from the available scattering data at low energy. The obtained results provide a clear evidence that the breakdown scale of the chiral expansion for this reaction is related to the $Δ$ -resonance. The explicit inclusion of the leading contributions of the $Δ$ -isobar is demonstrated to substantially increase the range of applicability of the effective field theory. The resulting predictions for the phase shifts are in an excellent agreement with the ones from the recent Roy-Steiner-equation analysis of pion-nucleon scattering.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.02640 [pdf]
PRC(2016)·60 citations
05
[Submitted on 8 Feb 2016]
A finite-temperature Hartree-Fock code for shell-model Hamiltonians
G.F. Bertsch · J.M Mehlhaff
The codes HFgradZ.py and HFgradT.py find axially symmetric minima of a Hartree-Fock energy functional for a Hamiltonian supplied in a shell-model basis. The functional to be minimized is the Hartree-Fock energy for zero-temperature properties or the Hartree-Fock grand potential for finite-temperature properties. Various constraints may be imposed on the minima.
Comments:
17 pages, 1 figure, Submitted to Computer Physics Communications
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1602.02727 [pdf]
Comput.Phys.Commun.(2016)·3 citations
06
[Submitted on 6 Feb 2016] (cross-list from hep-lat)
The topological structures in strongly coupled QGP with chiral fermions on the lattice
Sayantan Sharma🇺🇸 · Viktor Dick🇩🇪 · Frithjof Karsch🇺🇸 · Edwin Laermann🇩🇪 · Swagato Mukherjee🇺🇸
The nature of chiral phase transition for two flavor QCD is an interesting but unresolved problem. One of the most intriguing issues is whether or not the anomalous U(1) symmetry in the flavor sector is effectively restored along with the chiral symmetry. This may determine the universality class of the chiral phase transition. Since the physics near the chiral phase transition is essentially non-perturbative, we employ first principles lattice techniques to address this issue. We use overlap fermions, which have exact chiral symmetry on the lattice, to probe the anomalous U(1) symmetry violation of 2+1 flavor dynamical QCD configurations with domain wall fermions. The latter also optimally preserves chiral and flavor symmetries on the lattice, since it is known that the remnant chiral symmetry of the light quarks influences the scaling of the chiral condensate in the crossover transition region. We observe that the anomalous U(1) is not effectively restored in the chiral crossover region. We perform a systematic study of the finite size and cut-off effects since the signals of U(1) violation are sensitive to it. We also provide a glimpse of the microscopic topological structures of the QCD medium that are responsible for the strongly interacting nature of the quark gluon plasma phase. We study the effect of these microscopic constituents through our first calculations for the topological susceptibility of QCD at finite temperature, which could be a crucial input for the equation of state for anomalous hydrodynamics.
Comments:
4 Pages, 3 Figures, Proceedings of Quark Matter 2015, Kobe, Japan, version accepted for publication in Nucl. Phys. A
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.02197 [pdf]
NPA(2016)·21 citations
07
[Submitted on 6 Feb 2016] (cross-list from hep-th)
Three-body force for baryons from the D0-D4/D8 matrix model
Si-wen Li🇨🇳 · Tuo Jia🇨🇳
This is an extensive work to our previous paper \cite{key-08} studied on the D0-D4/D8 holographic system. We compute the three-body force for baryons with the D0-D4/D8 matrix model derived in \cite{key-08} with considering the non-zero QCD vacuum. We obtain the three-body force at short distances but modified by the appearance of the smeared D0-branes i.e. considering the effects from the non-trivial QCD vacuum. We firstly test our matrix model in the case of 't Hooft instanton and then in two more realistic case: (1) three-neutrons with averaged spins and (2) proton-proton-neutron (or proton-neutron-proton). The three-body potential vanishes in the former case while in two latter cases it is positive i.e. repulsive and makes sense only if the constraint for stable baryonic state is satisfied. We require all the baryons in our computation aligned on a line. These may indicate that the cases in dense states of neutrons such as in neutron stars, Helium-3 or Tritium nucleus all with the non-trivial QCD vacuum.
Comments:
24 pages
Subjects:
High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1602.02259 [pdf]
PRD(2016)·12 citations
08
[Submitted on 7 Feb 2016] (cross-list from hep-ph)
Analytic Bethe-Salpeter Description of the Lightest Pseudoscalar Mesons
Wolfgang Lucha🇦🇹 · Franz F. Schöberl🇦🇹
Within the Bethe-Salpeter formalism for instantaneous interactions, we describe, along a totally analytic route, the lightest pseudoscalar mesons by quark-antiquark bound states which show at least three indispensable general features, namely, the (almost) masslessness required for pions and kaons to be interpretable as (pseudo) Goldstone bosons, the suitable asymptotic behaviour in the limit of large spacelike relative momenta as determined by the relationship between quark mass function and Bethe-Salpeter amplitudes, and a pointwise behaviour for finite spacelike relative momenta suited for guaranteeing colour confinement.
Comments:
15 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1602.02356 [pdf]
PRD(2016)·21 citations
09
[Submitted on 8 Feb 2016] (cross-list from hep-ph)
Nuclear effects in deep inelastic scattering and transition region
S. Kumano (KEK/J-PARC)🇯🇵
We discuss nuclear effects on neutrino-nuclear interactions in a wide kinematical range from shallow to deep inelastic scattering (DIS) region. There is necessity from neutrino communities to have precise neutrino-nucleus cross sections for future measurements on neutrino oscillations and leptonic CP violation. We try to create a model to calculate neutrino cross sections in the wide kinematical range, from quasi-elastic scattering and resonance productions to the DIS. In this article, nuclear modifications of structure functions are mainly discussed, and a possible extension to the $Q^{2} \to 0$ region is explained. We also comment on the transition region between baryon resonances and the DIS. There are ongoing experimental efforts on nuclear modifications of structure functions or parton distribution functions such as by pA reactions at RHIC and LHC, Drell-Yan measurements at Fermilab, Miner $ν$ a neutrino DIS, and charged-lepton DIS at JLab.
Comments:
8 pages, LaTeX, 2 style files, 6 eps files, JPS Conference Proceedings in press, International workshop on Neutrino-Nucleus Interactions in the Few-GeV Region (NuInt15), Osaka, Japan, November 16-21, 2015
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1602.02459 [pdf]
JPS Conf.Proc.(2016)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE