Near-thermal equilibrium with Tsallis distributions in heavy ion collisions

TL;DR

This paper explores the use of Tsallis distributions in thermal models of heavy ion collisions, finding improved fits at SPS energies and suggesting a near-thermal equilibrium state with minimal fluctuations at RHIC energies.

Contribution

It introduces the application of Tsallis distributions to heavy ion collision data, enhancing fit quality and providing new insights into freeze-out conditions.

Findings

Better fit quality at SPS energies with Tsallis distributions.

No significant improvement at RHIC energies, indicating a stable freeze-out temperature.

Evidence of near-thermal equilibrium with minimal fluctuations at RHIC.

Abstract

Hadron yields in high energy heavy ion collisions have been fitted and reproduced by thermal models using standard statistical distributions. These models give insight into the freeze-out conditions at varying beam energies. In this paper we investigate changes to this analysis when the statistical distributions are replaced by Tsallis distributions for hadrons. We investigate the appearance of near-thermal equilibrium state at SPS and RHIC energies. We obtain better fits with smaller chi^2 for the same hadron data, as applied earlier in the thermal fits for SPS energies but not for RHIC energies. This result indicates that at RHIC energies the final state is very well described by a single freeze-out temperature with very little room for fluctuations.