Signatures of the strongly interacting QGP in relativistic heavy-ion collisions

TL;DR

This paper investigates signatures of the quark-gluon plasma (QGP) in relativistic heavy-ion collisions using transport models, highlighting the influence of the partonic phase on particle production and jet correlations, and comparing to experimental data.

Contribution

It introduces the use of the PHSD transport approach to identify QGP signatures in heavy-ion collisions and compares results with the HSD model lacking a phase transition.

Findings

Partonic phase affects kaon transverse mass distributions.

Enhanced production of multi-strange antibaryons due to QGP.

HSD model fails to reproduce jet suppression and correlation structures observed experimentally.

Abstract

The transition from hadronic to partonic degrees of freedom in the course of a relativistic heavy-ion collision is described by the microscopic covariant Parton-Hadron-String Dynamics (PHSD) transport approach. Studying Pb+Pb reactions from 40 to 158 AGeV and comparing the PHSD results to those of the Hadron-String Dynamics (HSD) approach without a phase transition to the QGP, we observe that the existence of the partonic phase has a sizable influence on the transverse mass distribution of final kaons due to the repulsive partonic mean fields. Furthermore, we find a significant effect of the QGP on the production of multi-strange antibaryons due to a slightly enhanced ssbar pair production in the partonic phase from massive time-like gluon decay and to a more abundant formation of strange antibaryons in the hadronization process. Another evidence for pre-hadronization dynamics is gained from a study of di-jet correlations in Au+Au collisions at the top RHIC energy of sqrt(S)=200 GeV. Within the HSD transport approach, the reaction of the hadronic medium to the jet energy loss is calculated. In comparison with the data of the STAR, PHOBOS and PHENIX Collaborations differentially in azimuthal angle and pseudorapidity, the HSD results do not show enough suppression for the `away-side' jet. In addition, the HSD results exhibit neither a `Mach-cone' structure for the angular distribution in the away-side jet nor the `ridge' long-range rapidity correlations for the near-side jet as observed by the STAR and PHOBOS Collaborations, thus suggesting a partonic origin of these structures.