Fluctuations of the $K/\pi$ Ratio in Nucleus-Nucleus Collisions: Statistical and Transport Models

TL;DR

This paper compares statistical and transport models to study event-by-event fluctuations of the kaon to pion ratio in nucleus-nucleus collisions, highlighting differences and challenges for future experimental validation.

Contribution

It demonstrates that the Hadron-String-Dynamics model can qualitatively reproduce fluctuation data and compares it with statistical models across different energies.

Findings

HSD model reproduces excitation function of $K/\pi$ fluctuations

Significant differences between HSD and statistical models

Predictions challenge future experimental measurements

Abstract

Event-by-event fluctuations of the kaon to pion number ratio in nucleus-nucleus collisions are studied within the statistical hadron-resonance gas model (SM) for different statistical ensembles and in the Hadron-String-Dynamics (HSD) transport approach. We find that the HSD model can qualitatively reproduce the measured excitation function for the $K/\pi$ ratio fluctuations in central Au+Au (or Pb+Pb) collisions from low SPS up to top RHIC energies. Substantial differences in the HSD and SM results are found for the fluctuations and correlations of the kaon and pion numbers. These predictions impose a challenge for future experiments.