Parton/hadron dynamics in heavy-ion collisions at FAIR energies

TL;DR

This paper analyzes heavy-ion collision data from STAR using transport models to explore partonic and hadronic phases, supporting a crossover transition and highlighting the sensitivity of kaon flow to hadronic potentials at FAIR energies.

Contribution

It demonstrates the effectiveness of PHSD/HSD models in describing collision data and provides evidence for a crossover quark-hadron transition at FAIR energies.

Findings

PHSD results roughly match STAR data.

Supports crossover quark-hadron transition.

Kaon flow sensitive to hadronic potentials at low energies.

Abstract

Recent STAR data for the directed flow of protons, antiprotons and charged pions obtained within the beam energy scan program are analyzed within the Parton-Hadron-String-Dynamics (PHSD/HSD) transport models. Both versions of the kinetic approach are used to clarify the role of partonic degrees of freedom. The PHSD results, simulating a partonic phase and its coexistence with a hadronic one, are roughly consistent with the STAR data. Generally, the semi-qualitative agreement between the measured data and model results supports the idea of a crossover type of quark-hadron transition which softens the nuclear EoS but shows no indication of a first-order phase transition. Furthermore, the directed flow of kaons and antikaons is evaluated in the PHSD/HSD approachesfrom $\sqrt{s_{NN}} \approx$ 3 - 200 GeV which shows a high sensitivity to hadronic potentials in the FAIR/NICA energy regime $\sqrt{s_{NN}} \le$ 8 GeV.