Experimental results on fluctuations of conserved charges confronted with predictions from canonical thermodynamics

TL;DR

This paper compares experimental measurements of particle charge fluctuations in nuclear collisions with theoretical predictions from canonical thermodynamics, highlighting non-dynamical effects and providing a framework for probing phase transitions.

Contribution

It offers quantitative estimates of non-dynamical fluctuation contributions using the Canonical Ensemble and compares these with experimental data from STAR.

Findings

Quantitative estimates of non-dynamical fluctuation effects.

Agreement between Monte Carlo simulations and experimental data.

Framework for analyzing fluctuations to probe phase transitions.

Abstract

The study of multiplicity distributions of identified particles in terms of their higher moments is at the focus of contemporary experimental and theoretical studies. In a thermalized system, combinations of these moments are directly related to the Equation of State (EoS). The ultimate goal of the experimental measurements in relativistic nuclear collisions is, by systematic comparison to QCD and QCD inspired calculations, to probe the dynamics of genuine phase transitions between a hadron gas and the quark-gluon plasma. However, the comparison between experiment and theory is far from trivial, because several non-dynamical effects on fluctuations need to be controlled prior to a meaningful comparison to theoretical predictions. In this report we present quantitative estimates for these non-dynamical contributions using the Canonical Ensemble (CE) formulation of statistical mechanics. Together with analytical formulas we provide also results from Monte Carlo (MC) simulations within the CE and compare our predictions with the corresponding measurements from the STAR experiment.