Probing freeze-out conditions in heavy ion collisions with moments of charge fluctuations

TL;DR

This paper uses the hadron resonance gas model to analyze moments of charge fluctuations in heavy ion collisions, comparing predictions with experimental data to probe freeze-out conditions and critical behavior.

Contribution

It provides a detailed calculation of fluctuation moments within the HRG model and compares them with experimental data, highlighting the potential of higher moments to detect critical phenomena.

Findings

Good agreement between model predictions and STAR data on net proton fluctuations.

Higher order moments are more sensitive to critical behavior.

Differences between HRG model and lattice QCD results are identified.

Abstract

We calculate the first four moments of baryon number, electric charge and strangeness fluctuations within the hadron resonance gas model. Different moments and their ratios as well as skewness and kurtosis are evaluated on the phenomenologically determined freeze-out curve in the temperature, baryon chemical potential plane. The model results and its predictions as well as relations between different moments are compared with the first data on net proton fluctuations in Au-Au collisions obtained at RHIC by the STAR Collaboration. We find good agreement between the model calculations and experimental results. We also point out that higher order moments should be more sensitive to critical behavior and will also distinguish hadron resonance gas model calculations from results obtained from lattice QCD.