Multiplicity Fluctuations in Limited Segments of Momentum Space in Statistical Models

TL;DR

This paper investigates multiplicity fluctuations in limited momentum space segments for a classical pion gas using statistical models, comparing different ensembles and predicting fluctuation behaviors relevant to phase transition signals.

Contribution

It provides a detailed analysis of multiplicity fluctuations across ensembles and offers qualitative predictions for experimental observables related to phase transitions in strongly interacting matter.

Findings

Correlations persist in large volume limits due to conservation laws.

Predicted fluctuation effects are comparable to phase transition signals.

Qualitative agreement with preliminary experimental data.

Abstract

Multiplicity fluctuations in limited segments of momentum space are calculated for a classical pion gas within the statistical model. Results for the grand canonical, canonical, and micro-canonical ensemble are obtained, compared and discussed. We demonstrate that even in the large volume limit correlations between macroscopic subsystems due to energy and momentum conservation persist. Based on the micro-canonical formulation we make qualitative predictions for the rapidity and transverse momentum dependence of multiplicity fluctuations. The resulting effects are of similar magnitude as the predicted enhancement due to a phase transition from a quark-gluon plasma to a hadron gas phase, or due to the critical point of strongly interacting matter, and qualitatively agree with recently published preliminary multiplicity fluctuation data of the NA49 SPS experiment.