Validity of the Hadronic Freeze-Out Curve

TL;DR

This study examines the hadronic freeze-out process in heavy-ion collisions using a hybrid model, revealing significant effects on antibaryon yields and implications for the freeze-out curve.

Contribution

It introduces a combined UrQMD and Statistical Hadronization Model approach to analyze the impact of the cascade phase on freeze-out parameters.

Findings

Antibaryon yields are strongly affected by the cascade phase.

The freeze-out temperature and chemical potential shift due to the cascade.

Implications for the shape and interpretation of the freeze-out curve.

Abstract

We analyze hadro-chemical freeze-out in central Pb+Pb collisions at CERN SPS energies, employing the hybrid version of UrQMD which models hadronization by the Cooper-Frye mechanism, and matches to a final hadron-resonance cascade. We fit the results both before and after the cascade stage using the Statistical Hadronization Model, to assess the effect of the cascade phase. We observe a strong effect on antibaryon yields except anti-{\Omega}, resulting in a shift in T and {\mu}_B. We discuss the implications for the freeze-out curve.