Fluctuations of Particle Yield Ratios in Heavy-Ion Collisions

TL;DR

This paper investigates the energy-dependent fluctuations of particle yield ratios in heavy-ion collisions, comparing experimental data with the hadron resonance gas model to understand underlying particle production processes.

Contribution

It introduces a detailed comparison of experimental fluctuations with HRG model predictions, highlighting the need for non-equilibrium effects at higher energies.

Findings

HRG with $eta=1$ fits SPS data well

Higher $eta$ needed for RHIC data

Fluctuations show non-monotonic energy dependence

Abstract

We study the dynamical fluctuations of various particle yield ratios at different incident energies. Assuming that the particle production yields in the hydronic final state are due to equilibrium chemical processes ($\gamma=1$), the experimental results available so far are compared with the hadron resonance gas model (HRG) taking into account the limited momentum acceptance in heavy-ion collisions experiments. Degenerated light and conserved strange quarks are presumed at all incident energies. At the SPS energies, the HRG with $\gamma=1$ provides a good description for the measured dynamical fluctuations in $(K^++K^-)/(\pi^++\pi^-)$. To reproduce the RHIC results, $\gamma$ should be larger than one. We also studied the dynamical fluctuations of $(p+\bar{p})/(\pi^++\pi^-)$. It is obvious that the energy-dependence of these dynamical fluctuations is non-monotonic.