Hadron Formation and the Phase Diagram of QCD Matter

TL;DR

This paper analyzes hadron production in heavy-ion collisions at low energies to understand the QCD phase diagram, using statistical models and transport simulations to identify freeze-out conditions as phase boundary indicators.

Contribution

It demonstrates that hadronic freeze-out points at low SPS energies universally mark the boundary of the hadronic phase in the QCD phase diagram.

Findings

No deviation from grand canonical equilibrium freeze-out observed.

Freeze-out points likely signal the boundary of the hadronic phase.

Supports the universality of freeze-out conditions across energies.

Abstract

We investigate hadronic species freeze-out systematics in A+A collisions at low SPS energies, corresponding to a baryochemical potential above 300 MeV, analyzing NA49 hadron production data in the framework of the statistical hadronization model, and in the UrQMD hadronic transport model. Observing no deviation from universal grand canonical hadro-chemical equilibrium freeze-out, we argue that the observed hadronic freeze-out points should universally signal the boundary line of the hadronic phase in the QCD matter phase diagram.