Locally anisotropic momentum distributions of hadrons at freeze-out in relativistic heavy-ion collisions

TL;DR

This paper introduces a spheroidal anisotropic momentum distribution in the statistical model of hadron production, showing it reproduces hadronic ratios and spectra similar to equilibrium models, and can improve agreement with experimental HBT data.

Contribution

It demonstrates that anisotropic momentum distributions can replace equilibrium assumptions without altering key observables, enhancing model flexibility.

Findings

Hadronic abundance ratios are unchanged by anisotropy when temperature is identified with transverse momentum scale.

Transverse-momentum spectra are nearly identical for isotropic and anisotropic systems with proper size adjustments.

Anisotropic models can better match experimental HBT results.

Abstract

A spheroidal anisotropic local momentum distribution is implemented in the statistical model of hadron production. We show that this form leads to exactly the same ratios of hadronic abundances as the equilibrium distributions, if the temperature is identified with a characteristic transverse-momentum scale. Moreover, to a very good approximation the transverse-momentum spectra of hadrons are the same for isotropic and anisotropic systems, provided the size of the system at freeze-out is appropriately adjusted. We further show that this invariance may be used to improve the agreement between the model and experimental HBT results.