Energy, Rapidity and Transverse Momentum Dependence of Multiplicity Fluctuations in Heavy Ion Collisions at CERN SPS

TL;DR

This study investigates how multiplicity fluctuations in heavy ion collisions depend on energy, rapidity, and transverse momentum, finding no signs of a critical point and comparing experimental results with theoretical models.

Contribution

It provides detailed measurements of multiplicity fluctuations across various energies and compares these with predictions from different theoretical models, highlighting discrepancies.

Findings

Scaled variance increases monotonically with energy from 0.8 to 1.2.

No evidence of the critical point in the fluctuation data.

UrQMD model reproduces the experimental scaled variance results.

Abstract

Multiplicity fluctuations in the forward hemisphere were studied for positively, negatively and all charged hadrons produced in central Pb+Pb collisions at 20A, 30A, 40A, 80A and 158A GeV. The multiplicity distributions and their scaled variances are presented as a function of collision energy, rapidity and transverse momentum. The distributions have a bell-like shape and the scaled variance changes monotonously with energy in the range from 0.8 to 1.2. No indication of the critical point is observed. The string-hadronic model UrQMD reproduces results on the scaled variance. The predictions of the hadron-resonance gas model obtained within the grand-canonical and canonical ensembles for the scaled variance disagree with the data.