Parton transport and hadronization from the dynamical quasiparticle point of view

TL;DR

This paper studies the hadronization process of an expanding partonic fireball using the PHSD approach based on a dynamical quasiparticle model, reproducing lattice QCD results and addressing the entropy problem.

Contribution

It introduces a dynamical quasiparticle model within the PHSD framework to describe parton hadronization, ensuring entropy increase and realistic particle ratios.

Findings

Elliptic flow $v_2$ correlates linearly with spatial eccentricity $$.

Hadronization via quark recombination increases entropy naturally.

Particle ratios align with a grandcanonical model at T  170 MeV.

Abstract

The hadronization of an expanding partonic fireball is studied within the Parton-Hadron-Strings Dynamics (PHSD) approach which is based on a dynamical quasiparticle model (DQPM) matched to reproduce lattice QCD results in thermodynamic equilibrium. Apart from strong parton interactions the expansion and development of collective flow is driven by strong gradients in the parton mean-fields. An analysis of the elliptic flow $v_2$ demonstrates a linear correlation with the spatial eccentricity $\epsilon$ as in case of ideal hydrodynamics. The hadronization occurs by quark-antiquark fusion or 3 quark/3 antiquark recombination which is described by covariant transition rates. Since the dynamical quarks become very massive, 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. This solves the entropy problem in hadronization in a natural way. The resulting particle ratios turn out to be in line with those from a grandcanonical partition function at temperature $T \approx 170$ MeV rather independent from the initial temperature and indicate an approximate strangeness equilibration.