Multiplicity fluctuations in heavy-ion collisions using canonical and grand-canonical ensemble

TL;DR

This paper investigates how multiplicity fluctuations in heavy-ion collisions differ between canonical and grand-canonical ensembles, especially at small conserved charge numbers, using an ideal thermal model with resonances.

Contribution

It provides a detailed comparison of higher order cumulants and their ratios for baryon, charge, and strangeness multiplicities in both ensembles, highlighting the importance of canonical treatment at small conserved charges.

Findings

Cumulant ratios vary significantly between ensembles at small conserved charges.

Canonical ensemble predictions differ from grand-canonical results for total and net-charge multiplicities.

Fluctuation patterns depend on collision energy and ensemble choice.

Abstract

We report the higher order cumulants and their ratios for baryon, charge and strangeness multiplicity in canonical and grand-canonical ensembles in ideal thermal model including all the resonances. When the number of conserved quanta is small, an explicit treatment of these conserved charges is required, which leads to a canonical description of the system and the fluctuations are significantly different from the grand canonical ensemble. Cumulant ratios of total charge and net-charge multiplicity as a function of collision energies are also compared in grand canonical ensemble.