Multiplicity fluctuations in the Glauber Monte Carlo approach

TL;DR

This paper investigates multiplicity fluctuations in nuclear collisions using Glauber Monte Carlo models, comparing wounded nucleon and wounded quark approaches, and introduces shadowing to better match experimental data.

Contribution

It demonstrates that wounded nucleon models fail to describe multiplicity fluctuations, while wounded quark models with shadowing successfully reproduce centrality dependence in Pb+Pb collisions.

Findings

Wounded Nucleon Model cannot reproduce scaled variance dependence.

Wounded Quark Model with shadowing matches experimental fluctuation data.

Shadowed quark sources are essential for accurate multiplicity predictions.

Abstract

We discuss multiplicity fluctuations of charged particles produced in nuclear collisions measured event-by-event by the NA49 experiment at CERN SPS within the Glauber Monte Carlo approach. We use the concepts of wounded nucleons and wounded quarks in the mechanism of multiparticle production to characterize multiplicity fluctuations expressed by the scaled variance of multiplicity distribution. Although Wounded Nucleon Model correctly reproduce the centrality dependence of the average multiplicity in Pb+Pb collisions, it completely fails in description of corresponding centrality dependence of scaled variance of multiplicity distribution. Using subnucleonic degrees of freedom, i.e. wounded quarks within Wounded Quark Model, it is possible to describe quite well the multiplicity distribution of charged particles produced in proton+proton interactions. However, the Wounded Quark Model with parameters describing multiplicity distribution of particles produced in proton+proton interactions substantially exceeds the average multiplicity of charged particles produced in Pb+Pb collisions. To obtain values of average multiplicities close to those experimentally measured in Pb+Pb collisions, the concept of shadowed quark sources is implemented. Wounded Quark Model with implemented shadowing source scenario reproduces the centrality dependence of scaled variance of multiplicity distribution of charged particles produced in Pb+Pb collisions in the range from the most central to mid-peripheral interactions.