Deconfinement of strangeness and freeze-out from charge fluctuations

TL;DR

This paper uses Lattice QCD to study the deconfinement of strangeness and proposes a model-independent method to determine freeze-out parameters in heavy-ion collisions, revealing their proximity to the QCD crossover region.

Contribution

It introduces a novel approach to determine freeze-out parameters directly from lattice calculations and experimental data, highlighting the persistence of strong interactions among strange quarks.

Findings

Strangeness deconfinement occurs in the chiral crossover region.

Strange quarks remain strongly interacting up to twice the crossover temperature.

Freeze-out parameters are close to the QCD crossover region, despite current inconsistencies.

Abstract

We use Lattice QCD calculations of fluctuations and correlations of various conserved charges to show that the deconfinement of strangeness takes place in the chiral crossover region of QCD; however, inside the quark-gluon plasma strange quarks remain strongly interacting at least up to temperatures twice the QCD crossover temperature. Further, we discuss how the freeze-out parameters of heavy-ion collisions can be determined in a model-independent way through direct comparisons between experimentally measured higher order cumulants of conserved charges and corresponding Lattice QCD calculations. Utilizing the preliminary data from the STAR and PHENIX experiments we illustrate this method. Although, the Lattice QCD based determinations of the freeze-out parameters utilizing data sets of different experiments and different observables are currently not consistent with each other, it is tantalizing to see that all the observed freeze-out parameters lie very close to the chiral/deconfinement crossover region of QCD.