Chemical freeze-out in heavy ion collisions at large baryon densities

TL;DR

This paper argues that chemical freeze-out in heavy ion collisions at high baryon densities occurs away from phase transitions, based on a linear nucleon-meson model calibrated with nuclear matter properties.

Contribution

It demonstrates that chemical freeze-out at high baryon densities is not linked to phase transitions, using a model consistent with nuclear matter data.

Findings

Freeze-out occurs at baryon densities below 15% of nuclear density.

The region of freeze-out is far from phase transition or crossover zones.

The linear nucleon-meson model reliably describes thermodynamics at relevant conditions.

Abstract

We argue that the chemical freeze-out in heavy ion collisions at high baryon density is not associated to a phase transition or rapid crossover. We employ the linear nucleon-meson model with parameters fixed by the zero-temperature properties of nuclear matter close to the liquid-gas quantum phase transition. For the parameter region of interest this yields a reliable picture of the thermodynamic and chiral properties at non-zero temperature. The chemical freeze-out observed in low-energy experiments occurs when baryon densities fall below a critical value of about 15 percent of nuclear density. This region in the phase diagram is far away from any phase transition or rapid crossover.