Mainz 2022 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 25: Heavy-Ion Collisions and QCD Phases VI
HK 25.5: Talk
Tuesday, March 29, 2022, 17:15–17:30, HK-H2
Ambiguities in the hadro-chemical freeze-out of Au+Au collisions at SIS18 energies and how to resolve them — •Anton Motornenko1, Jan Steinheimer1, Volodymyr Vovchenko3, Reinhard Stock4,1, and Horst Stoecker1,2,5 — 1FIAS, Frankfurt — 2ITP, Goethe Universität — 3Nuclear Science Division, LBL — 4IKP, Goethe Universität — 5GSI, Darmstadt
The thermal fit to preliminary HADES data of Au+Au collisions at √sNN=2.4 GeV shows two degenerate solutions at T≈50 MeV and T≈70 MeV. The analysis of the same particle yields in a transport simulation of the UrQMD model yields the same features, i.e. two distinct temperatures for the chemical freeze-out. While both solutions yield the same number of hadrons after resonance decays, the feeddown contribution is very different for both cases. This highlights that two systems with different chemical composition can yield the same multiplicities after resonance decays. The nature of these two minima is further investigated by studying the time-dependent particle yields and extracted thermodynamic properties of the UrQMD model. It is confirmed, that the evolution of the high temperature solution resembles cooling and expansion of a hot and dense fireball. The low temperature solution displays an unphysical evolution: heating and compression of matter with a decrease of entropy. These results imply that the thermal model analysis of systems produced in low energy nuclear collisions is ambiguous but can be interpreted by taking also the time evolution and resonance contributions into account. [1] Phys.Lett.B 822 (2021) 136703, arXiv:2104.06036 [hep-ph]