Nuclear Theory·nucl-th

Friday·April 3, 2015

6 papers—4 primary·2 cross-listed

01
[Submitted on 1 Apr 2015]
Effective distributions of quasi-particles for thermal photons
Akihiko Monnai🇺🇸
It has been found in recent heavy-ion experiments that the second and the third flow harmonics of direct photons are larger than most theoretical predictions. In this study, I construct effective parton phase-space distributions with in-medium interaction using quasi-particle models so that they are consistent with a lattice QCD equation of state. Then I investigate their effects on thermal photons using a hydrodynamic model. Numerical results indicate that elliptic flow and transverse momentum spectra are modified by the corrections to Fermi-Dirac and Bose-Einstein distributions.
Comments:
6 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1504.00406 [pdf]
PRC(2015)·7 citations
02
[Submitted on 2 Apr 2015]
Mass dependence of symmetry energy coefficients in Skyrme force
N. Wang · M. Liu · H. Jiang · J. L. Tian · Y. M. Zhao
Based on the semi-classical extended Thomas-Fermi approach, we study the mass dependence of the symmetry energy coefficients of finite nuclei for 36 different Skyrme forces. The reference densities of both light and heavy nuclei are obtained. Eight models based on nuclear liquid drop concept and the Skyrme force SkM* suggest the symmetry energy coefficient $a_{sym} = 22.90 \pm 0.15$ MeV at $A = 260$ , and the corresponding reference density is $ρ_{A} ≃ 0.1$ fm $^{- 3}$ at this mass region. The standard Skyrme energy density functionals give negative values for the coefficient of the $I^{4}$ term in the binding energy formula, whereas the latest Weizsäcker-Skyrme formula and the experimental data suggest positive values for the coefficient.
Comments:
6 figures, accepted for publication in Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.00455 [pdf]
PRC(2015)·25 citations
03
[Submitted on 2 Apr 2015]
Quantum design using a multiple internal reflections method in a study of fusion processes in the capture of alpha-particles by nuclei
Sergei P. Maydanyuk · Peng-Ming Zhang · Sergei V. Belchikov
A high precision method to determine fusion in the capture of $α$ -particles by nuclei is presented. For $α$ -capture by $^{40} Ca$ and $^{44} Ca$ , such an approach gives (1) the parameters of the $α$ --nucleus potential and (2) fusion probabilities. This method found new parametrization and fusion probabilities and decreased the error by $41.72$ times for $α +^{40} Ca$ and $34.06$ times for $α +^{44} Ca$ in a description of experimental data in comparison with existing results. We show that the sharp angular momentum cutoff proposed by Glas and Mosel is a rough approximation, Wong's formula and the Hill-Wheeler approach determine the penetrability of the barrier without a correct consideration of the barrier shape, and the WKB approach gives reduced fusion probabilities. Based on our fusion probability formula, we explain the difference between experimental cross-sections for $α +^{40} Ca$ and $α +^{44} Ca$ , which is connected with the theory of coexistence of the spherical and deformed shapes in the ground state for nuclei near the neutron magic shell $N = 20$ . To provide deeper insight into the physics of nuclei with the new magic number $N = 26$ , the cross-section for $α +^{46} Ca$ is predicted for future experimental tests. The role of nuclear deformations in calculations of the fusion probabilities is analyzed.
Comments:
46 pages, 23 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.00567 [pdf]
NPA(2015)·25 citations
04
[Submitted on 2 Apr 2015]
Quartic isospin asymmetry energy of nuclear matter from chiral pion-nucleon dynamics
N. Kaiser🇩🇪
Based on a chiral approach to nuclear matter, we calculate the quartic term in the expansion of the equation of state of isospin-asymmetric nuclear matter. The contributions to the quartic isospin asymmetry energy $A_{4} (k_{f})$ arising from $1 π$ -exchange and chiral $2 π$ -exchange in nuclear matter are calculated analytically together with three-body terms involving virtual $Δ (1232)$ -isobars. From these interaction terms one obtains at saturation density $ρ_{0} = 0.16$ fm $^{- 3}$ the value $A_{4} (k_{f 0}) = 1.5$ MeV, more than three times as large as the kinetic energy part. Moreover, iterated $1 π$ -exchange exhibits components for which the fourth derivative with the respect to the isospin asymmetry parameter $δ$ becomes singular at $δ = 0$ . The genuine presence of a non-analytical term $δ^{4} ln ∣ δ ∣$ in the expansion of the energy per particle of isospin-asymmetric nuclear matter is demonstrated by evaluating a s-wave contact interaction at second order.
Comments:
6 pages, 2 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1504.00604 [pdf]
PRC(2015)·46 citations
05
[Submitted on 2 Apr 2015] (cross-list from astro-ph.SR)
Exotic Phases in Magnetars
S. Schramm🇩🇪 · A. Bhattacharyya🇮🇳 · V. Dexheimer🇺🇸 · R. Mallick🇩🇪
Neutron stars feature extremely high magnetic fields with deduced field strengths of $1 0^{15}$ G in the case of magnetars and potentially much higher values inside of the star. In this context we consider the appearance of $ρ^{-}$ meson condensation taking into account the effect of the magnetic field. The results show that, depending on parameters, such a condensation in magnetized neutron stars might (just) occur.
Comments:
Contribution to the Proceedings of CSQCD IV, Prerow (2014)
Subjects:
Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1504.00451 [pdf]
1 citation
06
[Submitted on 2 Apr 2015] (cross-list from hep-ph)
Sequential Regeneration of Charmonia in Heavy-Ion Collisions
Xiaojian Du🇺🇸 · Ralf Rapp🇺🇸
We investigate the production of psi(2S) in nuclear collisions at RHIC and LHC energies. We first address charmonium production in 200 GeV d-Au collisions at RHIC; the strong suppression of psi' mesons observed in these reactions indicates mechanisms beyond initial cold nuclear matter effects. We find that a more complete treatment of hadronic dissociation reactions leads to appreciable psi' suppression in the hadronic medium of an expanding fireball background for d-Au collisions. When implementing the updated hadronic reaction rates into a fireball for 2.76 TeV Pb-Pb collisions at LHC, the regeneration of psi' mesons occurs significantly later than for J/psi's. Despite a smaller total number of regenerated psi', the stronger radial flow at their time of production induces a marked enhancement of their R_{AA} relative to J/psi's in a momentum range p_t \simeq 3-6 GeV. We explore the consequences and uncertainties of this "sequential regeneration" mechanism on the R_{AA} double ratio and find that it can reproduce the trends observed in recent CMS data.
Comments:
7 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1504.00670 [pdf]
NPA(2015)·227 citations

Affiliations

first authorsco-authorsvia INSPIRE

Effective distributions of quasi-particles for thermal photons

Mass dependence of symmetry energy coefficients in Skyrme force

Quantum design using a multiple internal reflections method in a study of fusion processes in the capture of alpha-particles by nuclei

Quartic isospin asymmetry energy of nuclear matter from chiral pion-nucleon dynamics

Exotic Phases in Magnetars

Sequential Regeneration of Charmonia in Heavy-Ion Collisions

Affiliations