Parton-Hadron-String Dynamics: an off-shell transport approach for relativistic energies

TL;DR

The paper introduces the PHSD off-shell transport approach to simulate relativistic nucleus-nucleus collisions, revealing the limited impact of the partonic phase on rapidity distributions but notable effects on transverse mass spectra and strange antibaryon production.

Contribution

It presents a novel off-shell transport model that incorporates partonic, hadronic, and string dynamics for relativistic collisions, providing new insights into the space-time evolution of such systems.

Findings

Large hadronic corona persists at top SPS energies.

Partonic phase influences transverse mass distributions of kaons.

Enhanced production of multi-strange antibaryons observed.

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 applied to Pb+Pb collisions from 20 to 160 A GeV in order to explore the space-time regions of 'partonic matter'. We find that even central collisions at the top-SPS energy of 158 A GeV show a large fraction of non-partonic, i.e. hadronic or string-like matter, which can be viewed as a hadronic corona. Furthermore, we observe that the partonic phase has a very low impact on rapidity distributions of hadrons but a sizeable influence on the transverse mass distribution of final kaons due to the repulsive partonic mean fields. We also find a significant effect on the production of multi-strange antibaryons due to a slightly enhanced $s{\bar s}$ pair production in the partonic phase from massive time-like gluon decay and a larger formation of antibaryons in the hadronization process. All differential hadron spectra are analyzed in comparison to the data of experimental collaborations.