Higher moments of net-proton multiplicity distributions in heavy ion collisions at chemical freeze-out

Abstract

The first four cumulants and ratios of cumulants of net-proton multiplicity distributions are calculated within the hadron resonance gas model. Quantum statistics, resonance decay contributions and the van der Waals excluded volume corrections are taken into account in the model calculations. The corrections due to quantum statistics are small even at the lower RHIC energies. The van der Waals excluded volume procedure leads to a larger suppression of the particle number fluctuations, especially for higher order cumulants. The STAR most central data on the various order cumulants and moment products at the higher RHIC energies are generally below the Poisson expectations and better described by the van der Waals gas with a hadron radius around r=0.3fm.