Cumulants of multiplicity distributions in most-central heavy-ion collisions

TL;DR

This paper studies how volume fluctuations affect multiplicity cumulants in heavy-ion collisions, showing that corrections mimic negative binomial distributions and are suppressed at central collisions, with implications for fluctuation analyses.

Contribution

It introduces a detailed analysis of volume correction effects on multiplicity cumulants using an optical Glauber model, highlighting the importance of volume fluctuations at central collisions.

Findings

Corrected cumulants resemble negative binomial distributions at non-central collisions.

Volume corrections tend to Poisson distributions at most-central collisions due to boundary effects.

External volume fluctuations significantly influence net proton and reference multiplicity distributions at central collisions.

Abstract

I investigate the volume corrections on cumulants of total charge distributions and net proton distributions. The required volume information is generated by an optical Glauber model. I find that the corrected statistical expectations of multiplicity distributions mimic the negative binomial distributions at non-central collisions, and they tend to approach the Poisson ones at most-central collisions due to the "boundary effects," which suppress the volume corrections. However, net proton distributions and reference multiplicity distributions are sensitive to the external volume fluctuations at most-central collisions, which imply that one has to consider the details of volume distributions in event-by-event multiplicity fluctuation studies.