Hadron Formation in Relativistic Nuclear Collisions and the QCD Phase Diagram

TL;DR

This paper investigates hadron formation in high-energy nuclear collisions, using the UrQMD model to derive survival factors that improve understanding of the QCD phase boundary by analyzing freeze-out conditions.

Contribution

It introduces a method to account for baryon and antibaryon annihilation effects during the final collision stage, refining the extraction of freeze-out parameters in heavy-ion collisions.

Findings

Survival factors resemble data deviations from statistical models.

Refined freeze-out points align closely with lattice QCD predictions.

Enhanced understanding of the QCD phase boundary in the $T-$ plane.

Abstract

We analyze hadrochemical freeze-out in central Pb+Pb collisions at CERN SPS and LHC energies. We determine the effects of baryon and antibaryon annihilation and/or regeneration occurring during the final cascade expansion stage of the collisions by deriving "survival factors" for each hadronic species and all energies considered by employing the UrQMD hybrid model. These survival factors are shown to resemble the pattern of data deviation from the statistical equilibrium calculations with the statistical model. We apply them in the SM data analysis, obtaining new points in the $T-\mu_B$ plane which follow closely the parton-hadron phase boundary predicted by lattice QCD.