Kinetic description of particle emission from expanding source

TL;DR

This paper presents a kinetic model for particle emission during the freeze out process in expanding relativistic heavy ion collision systems, emphasizing finite-time freeze out and analyzing its effects on particle distributions and entropy.

Contribution

It introduces a unified kinetic and expansion model with finite-time freeze out, providing new insights into the freeze out dynamics in heavy ion collisions.

Findings

Freeze out completes in finite time, affecting particle distributions.

Expansion does not smear out key freeze out features.

Entropy evolution is characterized in the model.

Abstract

The freeze out of the expanding systems, created in relativistic heavy ion collisions, is discussed. We combine kinetic freeze out equations with Bjorken type system expansion into a unified model. The important feature of the proposed scenario is that physical freeze out is completely finished in a finite time, which can be varied from 0 (freeze out hypersurface) to infinity. The dependence of the post freeze out distribution function on the freeze out time will be studied. As an example, model is completely solved and analyzed for the gas of pions. We shall see that the basic freeze out features, pointed out in the earlier works, are not smeared out by the expansion of the system. The entropy evolution in such a scenario is also studied.