Particle Freeze-out within the Self-Consistent Hydrodynamics

TL;DR

This paper critically examines hydrodynamic models of particle freeze-out, proposing a self-consistent formulation that avoids negative contributions in particle distributions and discusses common modeling pitfalls.

Contribution

It introduces a correct conservation law framework for particle emission from arbitrary freeze-out hypersurfaces, improving upon the Cooper-Frye formula.

Findings

Derived a positive-definite particle distribution function.

Identified limitations of current hydro models in freeze-out treatment.

Estimated the accuracy of modern hydrodynamic models at 10-15%.

Abstract

Here I discuss some implicit assumptions of modern hydrodynamic models and argue that their accuracy cannot be better than 10-15 %. Then I formulate the correct conservation laws for the fluid emitting particles from an arbitrary freeze-out (FO) hypersurface (HS) and show that the derived momentum distribution function of emitted particles does not contain negative contributions which appear in the famous Cooper-Frye formula. Further I analyze the typical pitfalls of some hydro models trying to alternatively resolve the FO problem.