Speaker
Description
The exploration of the phase diagram of quantum chromodynamics (QCD) is performed in
ultrarelativistic heavy-ion collision experiments, whereby the LHC and SPS facilities at CERN
Geneva and the RHIC at Brookhaven National Laboratory provide high-quality data on the
production of particles (hadrons and nuclei). While for the interpretation of the data a statistical
equilibrium approach (hadron resonance gas) is generally accepted, a quantum statistical description
of these strong nonequilibrium processes is needed, based on the time-dependent statistical operator
ρ(t).
In this talk, we outline Zubarev’s method of the nonequilibrium statistical operator (NSO) [1,2] as a
fundamental approach to describe nonequilibrium processes and present recent applications to
understand chemical freeze-out in the QCD phase diagram. We trace the origin of the freeze-out
lines to their correlation with the Mott lines for the dissociation of bound states in a hot and dense
medium [3-6].
[1] Zubarev, Morozov, Röpke, Statistical Mechanics of Nonequilibrium Processes II, Wiley (1997)
[2] D. Blaschke et al. (Eds.), Nonequilibrium Phenomena in Strongly Correlated Systems, Particles
(2020)
[3] Dönigus et al., PRC 106 (2022) 044908
[4] Blaschke et al., PLB 860 (2025) 139206
[5] Vitiuk et al., arXiv:2409.09019, PRC (2025)
[6] Röpke et al., arXiv:2411.00535
) supported by NCN under grant number 2021/43/P/ST2/03319
*) supported by a honorary stipend from the Foundation for Polish Science within the Alexander
von Humboldt program under grant No. DPN/JJL/402-4773/2022
