The quark susceptibility in a generalized dynamical quasiparticle model

Abstract

The quark susceptibility ${\chi }_q$ at zero and finite quark chemical potential provides a critical benchmark to determine the quark-gluon-plasma (QGP) degrees of freedom in relation to the results from lattice QCD (lQCD) in addition to the equation of state and transport coefficients. Here we extend the familiar dynamical-quasiparticle model (DQPM) to partonic propagators that explicitly depend on the three-momentum with respect to the partonic medium at rest in order to match perturbative QCD (pQCD) at high momenta. Within the extended dynamical-quasi-particle model (DQPM${}^{\ast }$) we reproduce simultaneously the lQCD results for the quark number density and susceptibility and the QGP pressure at zero and finite (but small) chemical potential ${\mu }_q$. The shear viscosity $\eta$ and the electric conductivity ${\sigma }_e$ from the extended quasiparticle model (DQPM${}^{\ast }$) also turn out in close agreement with lattice results for ${\mu }_q$ =0. The DQPM${}^{\ast }$, furthermore, allows to evaluate the momentum $p$, temperature $T$ and chemical potential ${\mu }_q$ dependencies of the partonic degrees of freedom also for larger ${\mu }_q$ which are mandatory for transport studies of heavy-ion collisions in the regime 5 GeV $<\sqrt{s_{NN}}<$ 10 GeV.

Comments: 12 pages, 11 figures