Covariant transport approach for strongly interacting partonic systems

TL;DR

This paper introduces a covariant transport approach (PHSD) for modeling strongly interacting partonic systems in relativistic nucleus-nucleus collisions, incorporating lattice-QCD results and detailed transition dynamics.

Contribution

The novel PHSD transport approach combines a dynamical quasiparticle model with covariant transition rates, providing a comprehensive framework for simulating partonic to hadronic matter in high-energy collisions.

Findings

Partonic phase significantly affects multi-strange antibaryon production.

Enhanced s-sbar pair production from gluon decay influences particle yields.

Sequential decay of high-mass pre-hadronic states increases total entropy.

Abstract

The dynamics of partons, hadrons and strings in relativistic nucleus-nucleus collisions is analyzed within the novel Parton-Hadron-String Dynamics (PHSD) transport approach, which is based on a dynamical quasiparticle model for partons (DQPM) matched to reproduce recent lattice-QCD results - including the partonic equation of state - in thermodynamic equilibrium. Scalar- and vector-interaction densities are extracted from the DQPM as well as effective scalar- and vector-mean fields for the partons. The transition from partonic to hadronic degrees of freedom is described by covariant transition rates for the fusion of quark-antiquark pairs or three quarks (antiquarks), respectively, obeying flavor current-conservation, color neutrality as well as energy-momentum conservation. Since the dynamical quarks and antiquarks become very massive close to the phase transition, the formed resonant 'pre-hadronic' color-dipole states ($q\bar{q}$ or $qqq$) are of high invariant mass, too, and sequentially decay to the groundstate meson and baryon octets increasing the total entropy. When applying the PHSD approach to Pb+Pb colllisions at 158 A$\cdot$GeV we find a significant effect of the partonic phase on the production of multi-strange antibaryons due to a slightly enhanced $s{\bar s}$ pair production from massive time-like gluon decay and a larger formation of antibaryons in the hadronization process.