Hadron multiplicities and chemical freeze-out conditions in proton-proton and nucleus-nucleus collisions

TL;DR

This study compares hadron multiplicities and chemical freeze-out conditions in proton-proton and nucleus-nucleus collisions across a range of energies, revealing differences in freeze-out temperatures using statistical models.

Contribution

It provides new analysis of mean hadron multiplicities in p+p interactions and compares chemical freeze-out parameters with those in heavy-ion collisions using HRG models.

Findings

Freeze-out temperatures are higher in p+p interactions than in nucleus-nucleus collisions.

The HRG model describes multiplicities using canonical ensemble for p+p and grand canonical for heavy-ion collisions.

Chemical freeze-out parameters vary with collision energy and system type.

Abstract

New results of the NA61/SHINE Collaboration at the CERN SPS on mean hadron multiplicities in proton-proton (p+p) interactions are analyzed within the transport models and the hadron resonance gas (HRG) statistical model. The chemical freeze-out parameters in p+p interactions and central Pb+Pb (or Au+Au) collisions are found and compared with each other in the range of the center of mass energy of the nucleon pair $\sqrt{s_{NN}}=3.2-17.3$ GeV. The canonical ensemble formulation of the HRG model is used to describe mean hadron multiplicities in p+p interactions and the grand canonical ensemble in central Pb+Pb and Au+Au collisions. The chemical freeze-out temperatures in p+p interactions are found to be larger than the corresponding temperatures in central nucleus-nucleus collisions.