Strongly Intensive Measures for Multiplicity Fluctuations

TL;DR

This paper investigates strongly intensive measures of multiplicity fluctuations in nucleus-nucleus collisions using the HSD model, comparing results with experimental data and analyzing their energy and centrality dependence.

Contribution

It introduces and studies the behavior of $ riangle^{K ext{pi}}$ and $oldsymbol{ extSigma^{K extpi}}$ measures within the HSD model, highlighting their ability to suppress participant fluctuations and analyzing their energy dependence.

Findings

HSD reasonably reproduces $oldsymbol{ extSigma^{K extpi}}$ data.

$oldsymbol{ extDelta^{K extpi}}$ shows a structure not captured by HSD.

Participant fluctuations are effectively canceled by these measures.

Abstract

The recently proposed two families of strongly intensive measures of fluctuations and correlations are studied within Hadron-String-Dynamics (HSD) transport approach to nucleus-nucleus collisions. We consider the measures $\Delta^{K\pi}$ and $\Sigma^{K\pi}$ for kaon and pion multiplicities in Au+Au collisions in a wide range of collision energies and centralities. These strongly intensive measures appear to cancel the participant number fluctuations. This allows to enlarge the centrality window in the analysis of event-by-event fluctuations up to at least of 10% most central collisions. We also present a comparison of the HSD results with the data of NA49 and STAR collaborations. The HSD describes $\Sigma^{K\pi}$ reasonably well. However, the HSD results depend monotonously on collision energy and do not reproduce the bump-deep structure of $\Delta^{K\pi}$ observed from the NA49 data in the region of the center of mass energy of nucleon pair $\sqrt{s_{NN}}= 8\div 12$ GeV. This fact deserves further studies. The origin of this `structure' is not connected with simple geometrical or limited acceptance effects, as these effects are taken into account in the HSD simulations.