Event-by-event multiplicity fluctuations in Pb-Pb collisions in ALICE

TL;DR

This paper analyzes event-by-event multiplicity fluctuations in Pb-Pb collisions at LHC energies, focusing on the scaled variance of charged-particle multiplicity distributions across different collision centralities.

Contribution

It provides the first detailed measurement of scaled variance of multiplicity fluctuations as a function of centrality in Pb-Pb collisions at LHC energies.

Findings

Scaled variance varies with collision centrality.

Volume fluctuations significantly influence multiplicity fluctuations.

Results serve as vital input for theoretical models.

Abstract

Fluctuations of various observables in heavy-ion collisions at ultra-relativistic energies have been extensively studied as they provide important signals regarding the formation of a Quark-Gluon Plasma (QGP). Because of the large number of produced particles in each event, a detailed study of event-by-event multiplicity fluctuations has been proposed as one of the signatures of the phase transition. In addition, the understanding of multiplicity fluctuations is essential for other event-by-event measurements. In the present work, we have calculated the scaled variance ($\omega_{\rm ch}=\sigma^{\rm 2} / \mu$) of the charged-particle multiplicity distributions as a function of centrality in Pb-Pb collisions at LHC energies. Here, $\mu$ and $\sigma$ denote the mean and the width of the multiplicity distributions, respectively. The trend of scaled variances as a function of centrality is presented and discussed. Volume fluctuations play an important role while measuring the multiplicity fluctuations, which are also discussed. The results are expected to provide vital input to theoretical model calculations.