The quark susceptibility in a generalized dynamical quasiparticle model

TL;DR

This paper extends the dynamical quasiparticle model to include momentum dependence, successfully matching lattice QCD results for quark susceptibility, density, pressure, and transport coefficients at finite chemical potential, aiding heavy-ion collision studies.

Contribution

The authors develop an extended dynamical quasiparticle model (DQPM$^*$) with explicit momentum dependence, aligning with lattice QCD data and enabling exploration of higher chemical potentials.

Findings

DQPM$^*$ reproduces lattice QCD results for quark density and susceptibility.

DQPM$^*$ matches lattice results for shear viscosity and electric conductivity at zero chemical potential.

The model allows investigation of partonic properties at larger chemical potentials relevant for heavy-ion collisions.

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$^*$) 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$^*$) also turn out in close agreement with lattice results for $\mu_q$ =0. The DQPM$^*$, 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.