Beyond the thermal model in relativistic heavy-ion collisions

TL;DR

This paper investigates deviations from thermal distributions in relativistic heavy-ion collisions, focusing on rapidity distributions to understand nonequilibrium processes and the contributions of different sources over time.

Contribution

It introduces a method to analyze rapidity distributions to distinguish between equilibrium and nonequilibrium particle sources in heavy-ion collisions.

Findings

Deviations indicate presence of nonequilibrium processes.

Rapidity distributions reveal the fraction of particles from different sources.

Thermal equilibrium is only achieved at very large times.

Abstract

Deviations from thermal distribution functions of produced particles in relativistic heavy-ion collisions are discussed as indicators for nonequilibrium processes. The focus is on rapidity distributions of produced charged hadrons as functions of collision energy and centrality which are used to infer the fraction of produced particles from a central fireball as compared to the one from the fragmentation sources that are out of equilibrium with the rest of the system. Overall thermal equilibrium would only be reached for large times t -> infinity.