Nuclear Theory·nucl-th

Tuesday·December 29, 2015

19 papers—12 primary·7 cross-listed

01
[Submitted on 25 Dec 2015]
Microscopic nuclear structure models and methods : Chiral symmetry, Wobbling motion and $γ -$ bands
J. A. Sheikh · G. H. Bhat · W. A. Dar · S. Jehangir · P. A. Ganai
A systematic investigation of the nuclear observables related to the triaxial degree of freedom is presented using the multi-quasiparticle triaxial projected shell model (TPSM) approach. These properties correspond to the observation of $γ$ -bands, chiral doublet bands and the wobbling mode. In the TPSM approach, $γ$ -bands are built on each quasiparticle configuration and it is demonstrated that some observations in high-spin spectroscopy that have remained unresolved for quite some time could be explained by considering $γ$ -bands based on two-quasiparticle configurations. It is shown in some Ce-, Nd- and Ge-isotopes that the two observed aligned or s-bands originate from the same intrinsic configuration with one of them as the $γ$ -band based on a two-quasiparticle configuration. In the present work, we have also performed a detailed study of $γ$ -bands observed up to the highest spin in Dysposium, Hafnium, Mercury and Uranium isotopes. Furthermore, several measurements related to chiral symmetry breaking and wobbling motion have been reported recently. These phenomena, which are possible only for triaxial nuclei, have been investigated using the TPSM approach. It is shown that doublet bands observed in lighter odd-odd Cs-isotopes can be considered as candidates for chiral symmetry breaking. Transverse wobbling motion recently observed in $^{135}$ Pr has also been investigated and it is shown that TPSM approach provides a reasonable description of the measured properties.
Comments:
Submitted to special Physica Scripta edition "Focus Issue on Nuclear Structure: Celebrating the 75 Nobel Prize" in Physics
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1512.07967 [pdf]
Phys.Scripta(2016)·47 citations
02
[Submitted on 25 Dec 2015]
Remembrance of things past: non-equilibrium effects and the evolution of critical fluctuations near the QCD critical point
Swagato Mukherjee🇺🇸 · Raju Venugopalan🇺🇸 · Yi Yin🇺🇸
We report on recent progress in the study of the evolution of non-Gaussian cumulants of critical fluctuations. We explore the implications of non-equilibrium effects on the search for the QCD critical point.
Comments:
Proceedings of Quark Matter 2015, (Sep. 27-Oct. 3, Kobe, Japan)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1512.08022 [pdf]
NPA(2016)·0 citations
03
[Submitted on 25 Dec 2015]
Hadron multiplicities and chemical freeze-out conditions in proton-proton and nucleus-nucleus collisions
V. Vovchenko🇩🇪 · V. V. Begun🇵🇱 · M. I. Gorenstein🇺🇦
New results of the NA61/SHINE Collaboration at the CERN SPS on mean hadron multiplicities in proton-proton (p+p) interactions are analyzed within the transport models and the hadron resonance gas (HRG) statistical model. The chemical freeze-out parameters in p+p interactions and central Pb+Pb (or Au+Au) collisions are found and compared with each other in the range of the center of mass energy of the nucleon pair $s_{N N} = 3.2 - 17.3$ GeV. The canonical ensemble formulation of the HRG model is used to describe mean hadron multiplicities in p+p interactions and the grand canonical ensemble in central Pb+Pb and Au+Au collisions. The chemical freeze-out temperatures in p+p interactions are found to be larger than the corresponding temperatures in central nucleus-nucleus collisions.
Comments:
Some misprints are corrected in the text, as well as in Fig.1(f)
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1512.08025 [pdf]
PRC(2016)·126 citations
04
[Submitted on 26 Dec 2015]
Effective QCD and transport description of dilepton and photon production in heavy-ion collisions and elementary processes
O. Linnyk🇩🇪 · E. L. Bratkovskaya🇩🇪 · W. Cassing🇩🇪
In this review we address the dynamics of relativistic heavy-ion reactions and in particular the information obtained from electromagnetic probes that stem from the partonic and hadronic phases. The out-of-equilibrium description of strongly interacting relativistic fields is based on the theory of Kadanoff and Baym. For the modeling of the partonic phase we introduce a dynamical quasiparticle model (DQPM) for QCD in equilibrium. The widths and masses of the quasiparticles are controlled by transport coefficients in comparison to lattice QCD results. The resulting off-shell transport approach - denoted by Parton-Hadron-String Dynamics (PHSD) - also includes covariant dynamical hadronization and keeps track of the hadronic interactions in the final phase. We show that PHSD captures the bulk dynamics of heavy-ion collisions from SPS to LHC energies and provides a basis for the evaluation of the electromagnetic emissivity, using the same dynamical parton propagators as for the system evolution. Direct photon production in elementary processes and heavy-ion reactions at RHIC and LHC energies is investigated and the status of the photon v2 puzzle - a large elliptic flow of the direct photons observed in A+A collisions - is addressed. We discuss the roles of hadronic and partonic sources for the photon spectra and the flow coefficients v2 and v3 and also the possibility to subtract the QGP signal from observables. Furthermore, the production of dilepton pairs is addressed from SIS to LHC energies. The low-mass dilepton yield is enhanced due to the in-medium modification of the rho-meson and at the lowest energy also due to a multiple regeneration of Delta-resonances. In addition, a signal of the partonic degrees-of-freedom is found in the intermediate dilepton mass regime (1.2GeV<M<3GeV), which can shed light on the nature of the very early degrees-of-freedom in nucleus-nucleus collisions.
Comments:
review article to appear in the Progress in Particle and Nuclear Physics
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1512.08126 [pdf]
PPNP(2016)·174 citations
05
[Submitted on 27 Dec 2015]
Isoscalar dipole transition as a probe for asymmetric clustering
Y. Chiba · M. Kimura · Y. Taniguchi
Background: The sharp $1^{-}$ resonances with enhanced isoscalar dipole transition strengths are observed in many light nuclei at relatively small excitation energies, but their nature was unclear. Purpose: We show those resonances can be attributed to the cluster states with asymmetric configurations such as $α$ + $^{16} O$ . We explain why asymmetric cluster states are strongly excited by the isoscalar dipole transition. We also provide a theoretical prediction of the isoscalar dipole transitions in $^{20} Ne$ and $^{44} Ti$ . Method: The transition matrix is analytically derived to clarify the excitation mechanism. The nuclear model calculations by Brink-Bloch wave function and antisymmetrized molecular dynamics are also performed to provide a theoretical prediction for $^{20} Ne$ and $^{44} Ti$ . Results: It is shown that the transition matrix is as large as the Weisskopf estimate even though the ground state is an ideal shell model state. Furthermore, it is considerably amplified if the ground state has cluster correlation. The nuclear model calculations predict large transition matrix to the $α$ + $^{16} O$ and $α$ + $^{40} Ca$ cluster states comparable with or larger than the Weisskopf estimate. Conclusion: We conclude that the asymmetric cluster states are strongly excited by the isoscalar dipole transition. Combined with the isoscalar monopole transition that populates the $0^{+}$ cluster states, the isoscalar transitions are promising probe for asymmetric clusters.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1512.08214 [pdf]
PRC(2016)·57 citations
06
[Submitted on 27 Dec 2015]
New insights from 3D simulations of heavy ion collisions
Gabriel Denicol🇺🇸 · Akihiko Monnai🇺🇸 · Sangwook Ryu🇨🇦 · Bjoern Schenke🇺🇸
Viscous relativistic hydrodynamics in 3+1 dimensions is applied to describe heavy ion collisions at RHIC and LHC. We present calculations of observables that are sensitive to the longitudinal structure of the created system. In particular we present pseudo-rapidity correlations and demonstrate their dependence on both the initial state and short range correlations introduced via a microscopic transport description. We further demonstrate the effect of a varying temperature dependence of the shear viscosity to entropy density ratio on rapidity dependent flow harmonics.
Comments:
4 pages, 2 figures, Proceedings of the Quark Matter 2015 conference, September 27 - October 3, 2015, Kobe, Japan
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1512.08231 [pdf]
NPA(2016)·11 citations
07
[Submitted on 27 Dec 2015]
Pre-equilibrium dynamics and heavy-ion observables
Ulrich W. Heinz🇺🇸 · Jia Liu (Ohio State University)🇺🇸
To bracket the importance of the pre-equilibrium stage on relativistic heavy-ion collision observables, we compare simulations where it is modeled by either free-streaming partons or fluid dynamics. These cases implement the assumptions of extremely weak vs. extremely strong coupling in the initial collision stage. Accounting for flow generated in the pre-equilibrium stage, we study the sensitivity of radial, elliptic and triangular flow on the switching time when the hydrodynamic description becomes valid. Using the hybrid code iEBE-VISHNU we perform a multi-parameter search, constrained by particle ratios, integrated elliptic and triangular charged hadron flow, the mean transverse momenta of pions, kaons and protons, and the second moment $⟨ p_{T}^{2} ⟩$ of the proton transverse momentum spectrum, to identify optimized values for the switching time $τ_{s}$ from pre-equilibrium to hydrodynamics, the specific shear viscosity $η / s$ , the normalization factor of the temperature-dependent specific bulk viscosity $(ζ / s) (T)$ , and the switching temperature $T_{sw}$ from viscous hydrodynamics to the hadron cascade UrQMD. With the optimized parameters, we predict and compare with experiment the $p_{T}$ -distributions of $π$ , $K$ , $p$ , $Λ$ , $Ξ$ and $Ω$ yields and their elliptic flow coefficients, focusing specifically on the mass-ordering of the elliptic flow for protons and Lambda hyperons which is incorrectly described by VISHNU without pre-equilibrium flow.
Comments:
4 pages, 1 figure. Talk presented at Quark Matter 2015, Kobe, Sep. 27 - Oct. 3, 2015, to appear in the proceedings published by Nuclear Physics A. v2 corrects originally mislabeled curves in Figs. 2a,b
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1512.08276 [pdf]
NPA(2016)·27 citations
08
[Submitted on 28 Dec 2015]
Fission life-time calculation using a complex absorbing potential
Guillaume Scamps · Kouichi Hagino
A comparison between the semi-classical approximation and the full quantum calculation with a complex absorbing potential is made with a model of the fission of 258Fm. The potential barrier is obtained with the constrained Skyrme HF+BCS theory. The life-time obtained by the two calculations agree with each other the difference being only by 25%.
Comments:
5 pages, 2 figures, Conference proceedings of CNR*15 workshop, Tokyo, October 2015 to be published in EPJ Web of Conferences
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1512.08297 [pdf]
EPJ Web Conf.(2016)·0 citations
09
[Submitted on 28 Dec 2015]
Massive Neutron Stars with Hadron-Quark Transition Core : phenomenological approach by "3-window model"
Tatsuyuki Takatsuka🇯🇵 · Kota Masuda🇯🇵 · Tetsuo Hatsuda🇯🇵
By a new approach introducing a "3-window model" and constructing phenomenologically an equation of state for the hadron-quark (HQ) transition region, possible maximum mass of neutron stars (NSs) is discussed. It is found that neutron stars (NSs) with HQ transition core are able to have a mass exceeding two-solar mass, consistent with massive NSs recently observed.
Comments:
3 pages, 1 figure
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1512.08350 [pdf]
Proceedings of Quarks and Compact Stars,K…·0 citations
10
[Submitted on 28 Dec 2015]
Lambda-Lambda interaction from two-particle intensity correlation in relativistic heavy-ion collisions
Akira Ohnishi🇯🇵 · Kenji Morita🇯🇵 · Takenori Furumoto🇯🇵
We investigate $ΛΛ$ interaction dependence of the $ΛΛ$ intensity correlation in high-energy heavy-ion collisions. By analyzing the correlation data recently obtained by the STAR collaboration based on theoretically proposed $ΛΛ$ interactions, we give a constraint on the $ΛΛ$ scattering length, $- 1.25 fm < a_{0} < 0$ , suggesting that $ΛΛ$ interaction is weakly attractive and there is no loosely bound state. In addition to the fermionic quantum statistics and the $ΛΛ$ interaction, effects of collective flow, feed-down from $Σ^{0}$ , and the residual source are also found to be important to understand the data. We demonstrate that the correlation data favor negative $ΛΛ$ scattering length with the pair purity parameter $λ = (0.67)^{2}$ evaluated by using experimental data on the $Σ^{0} /Λ$ ratio, while the positive scattering length could be favored when we regard $λ$ as a free fitting parameter.
Comments:
Talk given at the 12th International Conference on Hypernuclear and Strange Particle Physics (HYP2015), Sendai, Japan, 7-12 Sep 2015, 8 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1512.08444 [pdf]
JPS Conf.Proc.(2017)·4 citations
11
[Submitted on 28 Dec 2015]
Approaches to QCD phase diagram; effective models, strong-coupling lattice QCD, and compact stars
Akira Ohnishi🇯🇵
The outline of the two lectures given in "Dense Matter School 2015" is presented. After an overview on the relevance of the phase diagram to heavy-ion collisions and compact star phenomena, I show some basic formulae to discuss the QCD phase diagram in the mean field treatment of the Nambu-Jona-Lasinio model. Next, I introduce the strong-coupling lattice QCD, which is one of the promising methods to access the QCD phase diagram including the first order phase boundary. In the last part, I discuss the QCD phase diagram in asymmetric matter, which should be formed in compact star phenomena.
Comments:
Lecture given at Helmholtz International Summer School "Dense Matter 2015", 29 June-11 July 2015 and the 15th International Conference on Strageness in Quark Matter (SQM 2015), 6-11 July 2015, Dubna, Russia. 12 pages, 10 figures. Some typos are corrected in v2
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat)
arXiv:
1512.08468 [pdf]
J.Phys.Conf.Ser.(2016)·11 citations
12
[Submitted on 28 Dec 2015]
The Middle of the Spectrum
Larry Zamick
There has been a great deal of attention to the low lying energy spectum in a nucleus becuse of the abundance of experimetal data. Likewise ,perhaps to a lesser extent but still significant the high end for a given configuratiion has been examined. Here ,using single j shell calculations as a guide we examine the middle part of the spectum resulting form single j shell calculations.Seniority arguments are used to partially explain the midshell behaviours even though in general seniority is not a good quantum number for mixed systems of neutrons and protons.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1512.08477 [pdf]
Phys. Rev. C93. 034327 (2016)·0 citations
13
[Submitted on 25 Dec 2015] (cross-list from hep-ph)
Surprisingly large uncertainties in temperature extraction from thermal fits to hadron yield data at LHC
Volodymyr Vovchenko🇩🇪 · Horst Stoecker🇩🇪
The conventional hadron-resonance gas (HRG) model with the Particle Data Group (PDG) hadron input, full chemical equilibrium, and the hadron type dependent eigenvolume interactions is employed to fit the hadron mid-rapidity yield data of ALICE Collaboration for the most central Pb+Pb collisions. For the case of point-like hadrons the well-known fit result $T = 154 \pm 2$ MeV is reproduced. However, the situation changes if hadrons have different eigenvolumes. In the case when all mesons are point-like while all baryons have an effective hard-core radius of 0.3 fm the $χ^{2}$ temperature dependence of the $χ^{2}$ has a broad minimum in the temperature range of $155 - 210$ MeV, with fit quality comparable to the $T \sim 155$ MeV minimum in the point-particle case. Very similar result is obtained when only baryon-baryon eigenvolume interactions are considered, with eigenvolume parameter taken from previous fit to ground state of nuclear matter. Finally, when we apply the eigenvolume corrections with mass-proportional eigenvolume $v_{i} \sim m_{i}$ , fixed to particular proton hard-core radius $r_{p}$ , we observe a second minimum in the temperature dependence of the $χ^{2}$ , located at the significantly higher temperatures. For instance, at $r_{p} = 0.5$ fm the fit quality is better than in the point-particle HRG case in a very wide temperature range of $170 - 320$ MeV, which gives an uncertainty in the temperature determination from the fit to the data of 150 MeV. These results show that thermal fits to the heavy-ion hadron yield data are very sensitive to the modeling of the short-range repulsion eigenvolume between hadrons, and that chemical freeze-out temperature can be extracted from the LHC hadron yield data only with sizable uncertainty.
Comments:
8 pages, 3 figures, v3: added calculations for baryon-baryon only eigenvolume interactions fitted to nuclear ground state, added table with fitted data, title and discussion modified in order to ensure more clarity about the presented results
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1512.08046 [pdf]
J.Phys.G(2017)·47 citations
14
[Submitted on 26 Dec 2015] (cross-list from hep-ph)
Origins of the di-jet asymmetry in heavy ion collisions
José Guilherme Milhano🇨🇭 · Korinna Christine Zapp🇨🇭
The di-jet asymmetry --- the measure of the momentum imbalance in a di-jet system --- is a key jet quenching observable. Using the event generator \jewel we show that the di-jet asymmetry is dominated by fluctuations both in proton-proton and in heavy ion collisions. We discuss how in proton-proton collisions the asymmetry is generated through recoil and out-of-cone radiation. In heavy ion collisions two additional sources contribute to the asymmetry, namely energy loss fluctuations and differences in path length. The latter is shown to be a sub-leading effect. We discuss the implications of our results for the interpretation of this observable.
Comments:
10 pages, 14 figures and 1 table. Added references, minor text clarifications
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1512.08107 [pdf]
EPJC(2016)·130 citations
15
[Submitted on 27 Dec 2015] (cross-list from hep-ph)
Spin Physics through QCD Instantons
Yachao Qian🇺🇸 · Ismail Zahed🇺🇸
We review some aspects of spin physics where QCD instantons play an important role. In particular, their large contributions in semi-inclusive deep-inelastic scattering and polarized proton on proton scattering. We also review their possible contribution in the $P$ -odd pion azimuthal charge correlations in peripheral $AA$ scattering at collider energies.
Comments:
19 pages, 14 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1512.08172 [pdf]
Annals Phys.(2016)·13 citations
16
[Submitted on 27 Dec 2015] (cross-list from hep-ph)
Strange matter and strange stars in a thermodynamically self-consistent perturbation model with running coupling and running strange quark mass
J. F. Xu🇨🇳 · G. X. Peng🇨🇳 · F. Liu🇨🇳 · D. F. Hou🇨🇳 · L. W. Chen🇨🇳
A quark model with running coupling and running strange quark mass, which is thermodynamically self-consistent at both high and lower densities, is presented and applied to study properties of strange quark matter and structure of compact stars. An additional term to the thermodynamic potential density is determined by meeting the fundamental differential equation of thermodynamics. It plays an important role in comparatively lower density and ignorable at extremely high density, acting as a chemical-potential dependent bag constant. In this thermodynamically enhanced perturbative QCD model, strange quark matter still has the possibility of being absolutely stable, while the pure quark star has a sharp surface with a maximum mass as large as about 2 times the solar mass and a maximum radius of about 11 kilometers.
Comments:
12 pages, 10 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1512.08229 [pdf]
PRD(2015)·48 citations
17
[Submitted on 27 Dec 2015] (cross-list from hep-ph)
Entropic destruction of a moving heavy quarkonium
Kazem Bitaghsir Fadafan🇮🇷 · Seyed Kamal Tabatabaei🇮🇷
Recently it has been shown that the peak of the quarkonium entropy at the deconfinement transition is related to the emergent entropic force which destructs the quarkonium. Using the AdS/CFT correspondence, we consider dissociation of a moving heavy quarkonium by entropic force. We find that the entropic force destructs the moving quarkonium easier than the static case which is expected from perturbative weakly coupled plasma. By considering the Maxwell charge, we study the effect of medium on the destruction of heavy quarkonium. It is shown that the quarkonium dissociates easier in the medium.
Comments:
10 pages, 8 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1512.08254 [pdf]
PRD(2016)·38 citations
18
[Submitted on 28 Dec 2015] (cross-list from hep-ph)
Heavy ion collisions and cosmology
Stefan Floerchinger🇩🇪
There are interesting parallels between the physics of heavy ion collisions and cosmology. Both systems are out-of-equilibrium and relativistic fluid dynamics plays an important role for their theoretical description. From a comparison one can draw interesting conclusions for both sides. For heavy ion physics it could be rewarding to attempt a theoretical description of fluid perturbations similar to cosmological perturbation theory. In the context of late time cosmology, it could be interesting to study dissipative properties such as shear and bulk viscosity and corresponding relaxation times in more detail. Knowledge and experience from heavy ion physics could help to constrain the microscopic properties of dark matter from observational knowledge of the cosmological fluid properties.
Comments:
8 pages, Plenary contribution to the proceedings of Quark Matter 2015, Kobe, Japan
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1512.08388 [pdf]
NPA(2016)·4 citations
19
[Submitted on 28 Dec 2015] (cross-list from hep-ph)
The Polyakov loop at next-to-next-to leading order
Matthias Berwein🇩🇪 · Nora Brambilla🇩🇪 · Peter Petreczky🇺🇸 · Antonio Vairo🇩🇪
We calculate the next-to-next-to-leading correction to the expectation value of the Polyakov loop or equivalently to the free energy of a static charge. This correction is of order $g^{5}$ . We show that up to this order the free energy of the static charge is proportional to the quadratic Casimir operator of the corresponding representation. We also compare our perturbative result with the most recent lattice results in SU(3) gauge theory.
Comments:
65 pages, 13 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
1512.08443 [pdf]
PRD(2016)·27 citations

Affiliations

first authorsco-authorsvia INSPIRE