Particle Freeze-out in Self-Consistent Relativistic Hydrodynamics

TL;DR

This paper develops a self-consistent relativistic hydrodynamic model for particle freeze-out, introducing a new approach that differs from the Cooper-Frye formula, especially for time-like hypersurface parts, leading to shock-like freeze-out.

Contribution

It presents a novel self-consistent formulation of particle emission in relativistic hydrodynamics that accounts for feedback and differs from traditional methods.

Findings

New freeze-out boundary conditions differ from Cooper-Frye for time-like surfaces.

The model predicts shock-like features in the freeze-out process.

Illustrative solutions demonstrate the impact of the new approach.

Abstract

The particle emission in relativistic hydrodynamic model is formulated assuming a sharp 3-dimensional space-time freeze-out hypersurface. The boundary conditions correspond to the energy-momentum and charge conservation between fluid and the gas of free particles. The emission and possible feedback of particles are included into the self-consistent hydrodynamic scheme. For the time-like parts of the freeze-out hypersurface the obtained results are different from the well known Cooper-Frye formula and lead to the shock-like freeze-out. A simple-wave hydrodynamic solution is considered in detail to illustrate some aspects of new freeze-out procedure.