Comment on "Investigation of Hadron Multiplicity and Hadron Yield Ratios in Heavy-Ion Collisions"

TL;DR

This paper critiques a proposed chemical freeze-out criterion in heavy-ion collision models, emphasizing the importance of recent literature and analyzing the validity of constant entropy per hadron against experimental data.

Contribution

It clarifies the relationship between different freeze-out criteria and demonstrates that constant entropy per hadron does not hold at high chemical potentials.

Findings

Constant entropy per hadron cannot remain constant at large chemical potentials.

The paper compares multiple freeze-out criteria against experimental results.

It highlights overlooked literature and clarifies theoretical assumptions.

Abstract

Oliinychenko, Bugaev and Sorin [arXiv:1204.0103 [hep-ph]] considered the role of conservation laws in discussing possible weaknesses of thermal models which are utilized in describing the hadron multiplicities measured in central nucleus-nucleus collisions. They argued to analyse the criteria for chemical freeze-out and to conclude that none of them were robust. Based on this, they suggested a new chemical freeze-out criterion. They assigned to the entropy per hadron the ad hoc value 7.18 and supposed to remain unchanged over the whole range of the baryo-chemical potentials. Due to unawareness of recent literature, the constant entropy per hadron has been discussed in Ref. [Fizika B18 (2009) 141-150, Europhys.Lett. 75 (2006) 420]. Furthermore, it has been shown that the constant entropy per hadron is equivalent to constant entropy normalized to cubic temperature, an earlier criterion for the chemical freeze-out introduced in Ref. [Europhys.Lett. 75 (2006) 420, Nucl.Phys.A764 (2006) 387-392]. In this comment, we list out the ignored literature, compare between the entropy-number density ratio and two criteria of averaged energy per averaged particle number and constant entropy per cubic temperature. All these criteria are confronted to the experimental results. The physics of constant entropy per number density is elaborated. It is concluded that this ratio can't remain constant, especially at large chemical potential related to AGS and SIS energies.