Nuclear Theory·nucl-th

Thursday·October 15, 2015

8 papers—2 primary·6 cross-listed

01
Shedding Light on the EOS-Gravity Degeneracy and Constraining the Nuclear Symmetry Energy from the Gravitational Binding Energy of Neutron Stars
Xiao-Tao He · F. J. Fattoyev · Bao-An Li · W. G. Newton
A thorough understanding of properties of neutron stars requires both a reliable knowledge of the equation of state (EOS) of super-dense nuclear matter and the strong-field gravity theories simultaneously. To provide information that may help break this EOS-gravity degeneracy, we investigate effects of nuclear symmetry energy on the gravitational binding energy of neutron stars within GR and the scalar-tensor subset of alternative gravity models. We focus on effects of the slope $L$ of nuclear symmetry energy at saturation density and the high-density behavior of nuclear symmetry energy. We find that the variation of either the density slope $L$ or the high-density behavior of nuclear symmetry energy leads to large changes in the binding energy of neutron stars. The difference in predictions using the GR and the scalar-tensor theory appears only for massive neutron stars, and even then is significantly smaller than the difference resulting from variations in the symmetry energy.
nucl-thastro-ph.SRgr-qcnucl-exEPJ Web Conf.(2016)·0 citations
02
Chiral symmetry restoration versus deconfinement in heavy-ion collisions at high baryon density
W. Cassing🇩🇪 · A. Palmese🇩🇪 · P. Moreau🇩🇪 · E. L. Bratkovskaya🇩🇪
We study the production of strange hadrons in nucleus-nucleus collisions from 4 to 160 A GeV within the Parton-Hadron-String Dynamics (PHSD) transport approach that is extended to incorporate essentials aspects of chiral symmetry restoration (CSR) in the hadronic sector (via the Schwinger mechanism) on top of the deconfinement phase transition as implemented in PHSD. Especially the $K^{+} / π^{+}$ and the $(Λ + Σ^{0}) / π^{-}$ ratios in central Au+Au collisions are found to provide information on the relative importance of both transitions. The modelling of chiral symmetry restoration is driven by the pion-nucleon $Σ$ -term in the computation of the quark scalar condensate $< q q ˉ >$ that serves as an order parameter for CSR and also scales approximately with the effective quark masses $m_{s}$ and $m_{q}$ . Furthermore, the nucleon scalar density $ρ_{s}$ , which also enters the computation of $< q q ˉ >$ , is evaluated within the nonlinear $σ - ω$ model which is constraint by Dirac-Brueckner calculations and low energy heavy-ion reactions. The Schwinger mechanism (for string decay) fixes the ratio of strange to light quark production in the hadronic medium. We find that above $\sim$ 80 A GeV the reaction dynamics of heavy nuclei is dominantly driven by partonic degrees-of-freedom such that traces of the chiral symmetry restoration are hard to identify. Our studies support the conjecture of 'quarkyonic matter' in heavy-ion collisions from about 5 to 40 A GeV and provide a microscopic explanation for the maximum in the $K^{+} / π^{+}$ ratio at about 30 A GeV which only shows up if a transition to partonic degrees-of-freedom is incorporated in the reaction dynamics and is discarded in the traditional hadron-string models.
nucl-thPRC(2016)·80 citations
03
Gluon shadowing effects on J/psi and Upsilon production in p+Pb collisions at sqrt s_NN = 115 GeV and Pb+p collisions at sqrt s_NN = 72 GeV at AFTER@LHC
R. Vogt🇺🇸
We explore the effects of shadowing on inclusive J/psi and Upsilon(1S) production at AFTER@LHC. We also present the rates as a function of p_T and rapidity for p+Pb and Pb+p collisions in the proposed AFTER@LHC rapidity acceptance.
↳ hep-phnucl-thAdv.High Energy Phys.(2015)·9 citations
04
Crystalline Ground States in Polyakov-loop extended Nambu--Jona-Lasinio Models
Jens Braun🇩🇪 · Felix Karbstein🇩🇪 · Stefan Rechenberger🇩🇪 · Dietrich Roscher🇩🇪
Nambu--Jona-Lasinio-type models have been used extensively to study the dynamics of the theory of the strong interaction at finite temperature and quark chemical potential on a phenomenological level. In addition to these studies, which are often performed under the assumption that the ground state of the theory is homogeneous, searches for the existence of crystalline phases associated with inhomogeneous ground states have attracted a lot of interest in recent years. In this work, we study the Polyakov-loop extended Nambu--Jona-Lasinio model and find that the existence of a crystalline phase is stable against a variation of the parametrization of the underlying Polyakov loop potential. To this end, we adopt two prominent parametrizations. Moreover, we observe that the existence of a quarkyonic phase depends crucially on the parametrization, in particular in the regime of the phase diagram where inhomogeneous chiral condensation is favored.
↳ hep-phnucl-thPRD(2016)·25 citations
05
New formulae for the $(- 2)$ moment of the photo-absorption cross section, $σ_{_{- 2}}$
Nico Orce
Two new formulae for the $(- 2)$ moment of the photo-absorption cross section, $σ_{_{- 2}}$ , have been determined, respectively, from the 1988 compilation of Dietrich and Berman and a mass-dependent symmetry energy coefficient, $a_{sy m} (A)$ . The data for $A ≳ 50$ follow, with a {\small $R M S$ } deviation of 6\%, the power-law $σ_{_{- 2}} = 2.4 A^{5/3}$ $μ$ b/MeV, which is in agreement with Migdal's calculation of $σ_{_{- 2}} = 2.25 A^{5/3}$ $μ$ b/MeV based on the hydrodynamic model and the $σ_{_{- 2}}$ sum rule. The additional inclusion of $a_{sy m} (A)$ provides a deeper insight to the nuclear polarization of $A ≧ 10$ nuclei.
↳ nucl-exnucl-thPRC(2015)·21 citations
06
Nuclear polarization effects in Coulomb excitation studies
Nico Orce
New polarization potentials have been determined based on: 1) the latest photo-neutron cross section evaluation and a missing factor of two in previous work, and 2) the mass dependency of the symmetry energy, $a_{sy m} (A)$ . The magnitude of the first one is 35\% stronger than the currently accepted polarization potential. The second one opens up the possibility for a parameter-free polarization potential. Both polarization potentials are essentially the same for heavy nuclei. The polarization effect on quadrupole collectivity is more substantial than previously assumed for light nuclei. Particular cases are discussed where long-standing discrepancies between high-precision Coulomb-excitation and lifetime measurements still remain. A solution to the long-standing discrepancy between $B (E 2; 0_{1}^{+} \to 2_{1}^{+})$ values determined in $^{18}$ O by several Coulomb-excitation studies and a high-precision lifetime measurement is provided in favor of the latter. Polarization effects in light nuclei also influence the determination of spectroscopic quadrupole moments in Coulomb-excitation measurements. The hindrance of polarizability observed in the photo-neutron cross section for single-closed shell nuclei is calculated to have a negligible effect on quadrupole collectivity, within the existing experimental uncertainties.
↳ nucl-exnucl-th0 citations
07
Theory @ Hard Probes 2015
Bjoern Schenke🇺🇸
Overview of the latest theory developments presented at the Hard Probes 2015 conference, held at McGill University, Montreal, Canada, in July 2015.
↳ hep-phnucl-thNucl.Part.Phys.Proc.(2016)·2 citations
08
Proof of Factorization of Heavy Quarkonium Production in Non-Equilibrium QCD at RHIC and LHC
Gouranga C Nayak
Recently we have proved the NRQCD factorization in heavy quarkonium production at high energy colliders at all orders in coupling constant. In this paper we extend this to non-equilibrium QCD and prove the NRQCD factorization in heavy quarkonium production at all orders in coupling constant in non-equilibrium QCD. This proof is necessary to study heavy quarkonium production from quark gluon plasma at RHIC and LHC.
↳ hep-phnucl-thEur.Phys.J.Plus(2018)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE