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Nuclear Theory·nucl-th

Wednesday·July 11, 2018

4 papers—3 primary·1 cross-listed

All4Primary3Cross-lists1
  1. 01

    Extraction of the Specific Shear Viscosity of Hot Hadron Gas

    Zhidong Yang🇺🇸 · Rainer J. Fries🇺🇸

    We extract the specific shear viscosity of nuclear matter for various temperatures and chemical potentials in the hadronic phase using data taken in high energy nuclear collisions. We use a blastwave parameterization of the final state of nuclear collisions, including non-equilibrium deformations of particle distributions due to shear stress in the Navier-Stokes approximation. We fit spectra and elliptic flow of identified hadrons for a variety of collision energies and impact parameters at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). The systems analyzed cover a temperature range from about 110 to 140 MeV and vary in their chemical potentials for stable hadrons. We attempt to assign meaningful systematic uncertainties to our results. This work is complementary to efforts using viscous fluid dynamics to extract the specific shear viscosity of quark gluon plasma at higher temperatures. We put our work in context with existing theoretical calculations of the specific shear viscosity.

    nucl-thhep-phnucl-ex4 citations
  2. 02

    Theoretical study of the capture of stable K and neutron-rich radioactive K by Ta

    Bing Wang🇨🇳 · Wei-Juan Zhao🇨🇳 · En-Guang Zhao🇨🇳 · Shan-Gui Zhou🇨🇳

    The empirical coupled-channel (ECC) model and the universal fusion function (UFF) prescription are used to analyse the data of capture cross sections for reactions KTa and KTa reported recently by A. Wakhle {\it et al.} [Phys. Rev. C 97, 021602(R) (2018)]. The results of the ECC model are in good agreement with the data of KTa while, for KTa, the predictions of the ECC model overestimate the above-barrier capture cross sections. Comparing the reduced data of these two reactions, it is found that the above-barrier cross sections of KTa are consistent with the UFF and are larger than those of KTa. This implies that the capture cross sections of KTa are suppressed at energies above the Coulomb barrier. Furthermore, at sub-barrier energies, the reduced calculated capture cross sections of KTa are a little larger than those of KTa, which is owing to the coupling to the positive -value two-neutron transfer channel.

    nucl-thnucl-exPRC(2018)·9 citations
  3. 03

    Thermal noise in non-boost-invariant dissipative hydrodynamics

    Chandrodoy Chattopadhyay🇮🇳 · Subrata Pal🇮🇳

    We study the effects of hydrodynamic fluctuations in non-boost-invariant longitudinal expansion of matter formed in relativistic heavy ion collisions. We formulate the theory of thermal noise within second-order viscous hydrodynamics treating noise as a perturbation on top of the non-boost-invariant flow. We develop a numerical simulation model to treat the (1+1)-dimension hydrodynamic evolution. The code is tested to reproduce the analytic results for the Riemann solver for expansion of matter in vacuum. For viscous hydrodynamic expansion, the initial energy density distribution are obtained by reproducing the measured charged hadron rapidity distribution at the RHIC energies. We show that the longitudinal rapidity correlations arising from space-time dependent thermal noise and from an induced thermal perturbation have distinct structures. In general, the rapidity correlations are found to be dominated by temperature fluctuations at small rapidity separation and velocity fluctuations at large rapidities. We demonstrate that thermal noise produce ridge-like two-particle rapidity correlations which persist at moderately large rapidities. The magnitude and pattern of the correlations are quite sensitive to various second-order dissipative formalisms and to the underlying equations of state, especially at large rapidities. The short-range part of the rapidity correlation is found to be somewhat enhanced as compared to that in boost-invariant flow of matter.

    nucl-thPRC(2018)·5 citations
  4. 04

    Signatures of quark-hadron phase transitions in general-relativistic neutron-star mergers

    Elias R. Most🇩🇪 · L. Jens Papenfort🇩🇪 · Veronica Dexheimer🇺🇸 · Matthias Hanauske🇩🇪 · Stefan Schramm🇺🇸 · Horst Stöcker🇩🇪 · Luciano Rezzolla🇩🇪

    Merging binaries of neutron stars are not only strong sources of gravitational waves, but also have the potential of revealing states of matter at densities and temperatures not accessible in laboratories. A crucial and long-standing question in this context is whether quarks are deconfined as a result of the dramatic increase in density and temperature following the merger. We present the first fully general-relativistic simulations of merging neutron stars including quarks at finite temperatures that can be switched off consistently in the equation of state. Within our approach, we can determine clearly what signatures a quark-hadron phase transition would leave in the gravitational-wave signal. In particular, we show that if the conditions are met for a phase transition to take place at several times nuclear saturation density, they would lead to a post-merger signal considerably different from the one expected from the inspiral, that can only probe the hadronic part of the equations of state, and to an anticipated collapse of the merged object. We also show that the phase transition leads to a very hot and dense quark core that, when it collapses to a black hole, produces a ringdown signal different from the hadronic one. Finally, in analogy with what is done in heavy-ion collisions, we use the evolution of the temperature and density in the merger remnant to illustrate the properties of the phase transition in a QCD phase diagram.

    ↳ astro-ph.HEgr-qcnucl-thPRL(2019)·459 citations

Affiliations

first authorsco-authorsvia INSPIRE