Studying Net-Proton Number Cumulants in a Modified van der Waals Hadron Resonance Gas

Abstract

The net-proton number cumulants are studied using an interacting hadron resonance gas (HRG) model that includes both attractive as well as van der Waals-type repulsive interaction among the hadrons. It is argued in this work that the van der Waals (VDW) parameters a and b corresponding to attractive and repulsive interactions are not constant and can have temperature and density dependence. We parametrize these VDW parameters as a function of temperature (T) and baryochemical potential (μ<inf>B</inf>). Therefore, the conventional van der Waals HRG (VDWHRG) model with constant parameters is now improved with modified van der Waals HRG (MVDWHRG) with T and μ<inf>B</inf> dependent VDW parameters. This leads to a substantial change in the thermodynamic properties of hadron gas as well as the higher-order conserved charge fluctuations in the high μ<inf>B</inf> and low T region. We adopt a simple parametrization to make it possible to study the net-proton fluctuation as a function of the centre of mass energy and compare it with the available experimental data. We observe that our results from MVDWHRG are in reasonable agreement with the experimental results. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.