Chemical Freeze-out of Strange Particles and Possible Root of Strangeness Suppression

TL;DR

This paper compares two methods for modeling the chemical freeze-out of strange particles in heavy-ion collisions, finding that a fully equilibrated approach better explains experimental data, especially for hyperons.

Contribution

It introduces an alternative fully equilibrated model for strange particle freeze-out based on conservation laws, improving data description over traditional non-equilibrium models.

Findings

The fully equilibrated approach describes hadron multiplicities with /dof = 1.06.

Conventional models show strangeness enhancement at low energies, contrary to suppression.

Fully equilibrated models better fit hyperon and antihyperon data.

Abstract

Two approaches to treat the chemical freeze-out of strange particles in hadron resonance gas model are analyzed. The first one employs their non-equillibration via the usual \gamma_s factor and such a model describes the hadron multiplicities measured in nucleus-nucleus collisions at AGS, SPS and RHIC energies with \chi^2/dof = 1.15. Surprisingly, at low energies we find not the strangeness suppression, but its enhancement. Also we suggest an alternative approach to treat the strange particle freeze-out separately, but with the full chemical equilibration. This approach is based on the conservation laws which allow us to connect the freeze-outs of strange and non-strange hadrons. Within the suggested approach the same set of hadron multiplicities can be described better than within the conventional approach with \chi^2/dof = 1.06. Remarkably, the fully equilibrated approach describes the strange hyperons and antihyperons much better than the conventional one.