May 17 – 22, 2021
US/Eastern timezone

Is the chemical freeze-out connected to the phase transition? A transport study of freeze-out criteria

May 19, 2021, 9:30 AM
Room A (Zoom)

Room A


zoom co-host: Niveditha Ramasubramanian
Theory talk Bulk (Transport)


Tom Reichert (Institut für Theoretische Physik, Goethe Universität Frankfurt)


The chemical freeze-out is often related to the phase transition to a deconfined state of matter, the Quark Gluon Plasma. We introduce a novel approach based on elastic and inelastic scattering rates to extract the hyper-surface of the chemical freeze-out from a hadronic transport simulation. We use the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model to extract the chemical freeze-out hyper-surface of pions and kaons in the energy range from E$_\mathrm{lab}$ = 1.23 AGeV to $\sqrt{s_\mathrm{NN}}$ = 62.4 GeV. By employing a coarse-graining procedure, we can extract the local temperature and baryo-chemical potential and investigate the typical freeze-out criteria $\langle$E$\rangle$/$\langle$N$\rangle$ = 1 GeV, s/T$^3$ = 7 and $n_B+n_\bar{B}$ = 0.12 fm$^{-3}$ on the chemical freeze-out surface and compare them to results from statistical model analysis. We find a great agreement leading to the conclusion that the chemical freeze-out can be well described by hadronic transport simulations. We do not observe a relation of the chemical freeze-out line and the phase-transition line. Instead we argue that the freeze-out line is defined by an interplay between elastic, inelastic and pseudo-elastic scattering rates and the expansion rate.

Primary authors

Tom Reichert (Institut für Theoretische Physik, Goethe Universität Frankfurt) Marcus Bleicher (Uni Frankfurt) Dr Gabriele Inghirami (GSI)

Presentation materials