Non-critical fluctuations of (net) charges and (net) protons from iEBE-VISHNU hybrid model

TL;DR

This study uses the iEBE-VISHNU hybrid model to analyze non-critical fluctuations of net charges and protons in Au+Au collisions at various energies, highlighting the dominant role of volume fluctuations.

Contribution

It demonstrates that the iEBE-VISHNU model can effectively reproduce experimental moments and cumulants, and identifies volume fluctuations as the main influence on multiplicity fluctuations.

Findings

Volume fluctuations dominate multiplicity fluctuations.

Hadronic evolution and resonance decays have minimal impact.

Model reproduces experimental data with proper tuning.

Abstract

In this paper, we investigate the non-critical fluctuations of (net) charges and (net) protons in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 39 and 200 GeV, using iEBE-VISHNU hybrid model with Poisson fluctuations added in the particle event generator between hydrodynamics and UrQMD. Various effects, such as volume fluctuations hadronic evolution and scatterings, resonance decays, as well as realistic centrality cuts and acceptance cuts have been embedded in our model calculations. With properly tuned parameters, iEBE-VISHNU roughly describe the centrality dependent moments and cumulants of (net) charges and (net) protons measured in experiment. Further comparison simulations show that the volume fluctuation is the dominant factor to influence the multiplicity fluctuations, which makes the higher moments of (net) charges largely deviate from the Poison baselines. We also find that the effects from hadronic evolutions and resonance decays are pretty small or even negligible for the multiplicity fluctuations of both (net) charges and (net) protons.