Chemical equilibration of QGP in hadronic collisions

TL;DR

This paper uses advanced QCD kinetic theory simulations to study how quark-gluon plasma chemically equilibrates in hadronic collisions, finding that equilibrium occurs after hydrodynamization but before thermalization, and that high-multiplicity collisions reach equilibrium across systems.

Contribution

It provides the first detailed simulation-based analysis of chemical equilibration timing in QGP during hadronic collisions, linking transport properties to system size and multiplicity.

Findings

Chemical equilibration occurs after hydrodynamization but before thermalization.

High-multiplicity collisions in various systems can reach chemical equilibrium.

Strangeness enhancement saturation occurs at similar multiplicities across collision types.

Abstract

We performed state-of-the-art QCD effective kinetic theory simulations of chemically equilibrating QGP in longitudinally expanding systems. We find that chemical equilibration takes place after hydrodynamization, but well before local thermalization. By relating the transport properties of QGP and the system size we estimate that hadronic collisions with final state multiplicities $dN_\text{ch}/d\eta > 10^2$ live long enough to reach approximate chemical equilibrium for all collision systems. Therefore we expect the saturation of strangeness enhancement to occur at the same multiplicity in proton-proton, proton-nucleus and nucleus-nucleus collisions.