Non-equilibrium approaches to the pre-thermal and post-hadronisation stages of A+A collisions

TL;DR

This paper discusses non-equilibrium phenomena in A+A collisions at early and late stages, using the HydroKinetic Model to successfully describe RHIC data and address the HBT puzzle.

Contribution

It introduces the HydroKinetic Model that incorporates non-equilibrium effects to accurately reproduce experimental data from RHIC collisions.

Findings

Good description of hadron momentum spectra

Successful explanation of pion and kaon interferometry data

Resolution of the HBT puzzle

Abstract

The results related to non-equilibrium phenomena at the very early and late stages of the processes of A+A collisions are presented. A good description of the hadron momentum spectra as well as pion and kaon interferometry data at RHIC is reached within the realistic dynamical picture of A+A collisions: HydroKinetic Model (HKM). The model accumulates the following features: not too early thermalization time; $\tau\geq 1$ fm/c; a developing of the pre-thermal transverse flows; the effectively more hard, than in the case of chemical equilibrium, equation of state of expanding chemically non-equilibrated multi-hadronic gas; a continuous non-equilibrated emission of hadrons. All these factors lead to a good description of the mentioned RHIC data, in particular, the observed $R_{out}/R_{side}$ ratios, solving, therefore, the HBT puzzle in detailed realistic model.