Possible interrelations among chemical freezeout conditions

TL;DR

This paper systematically compares various proposed chemical freezeout conditions in high-energy collisions, analyzing their physical meanings, sensitivities, and thermodynamic equivalences, suggesting they may reflect a single universal condition.

Contribution

It provides a comprehensive comparison of existing freezeout conditions, discusses their physical interpretations, and proposes they could be different facets of a universal freezeout criterion.

Findings

Most conditions are thermodynamically equivalent at low baryon chemical potential.

Some conditions align with recent lattice QCD calculations.

Further tests are needed at low energies to confirm universality.

Abstract

At thermal equilibrium, different chemical freezeout conditions have been proposed so far. They have an ultimate aim of proposing a universal description for the chemical freezeout parameters ($T_{ch}$ and $\mu_b$), which are to be extracted from the statistical fitting of different particle ratios measured at various collision energies with calculations from thermal models. A systematic comparison between these conditions is presented. The physical meaning of each of them and their sensitivity to the hadron mass cuts are discussed. Based on availability, some of them are compared with recent lattice calculations. We found that most of these conditions are thermodynamically equivalent, especially at small baryon chemical potential. We propose that further crucial consistency tests should be performed at low energies. The fireball thermodynamics is another way of guessing conditions describing the chemical freezeout parameters extracted from high-energy experiments. We endorse the possibility that the various chemical freezeout conditions should be interpreted as different aspects of one universal condition.