Statistical model analysis of hadron yields in proton-nucleus and heavy-ion collisions at SIS 18 energies

Abstract

The HADES data from p+Nb collisions at center of mass energy of $\sqrt{s_{NN}}$= 3.2 GeV are analyzed by employing a statistical model. Accounting for the identified hadrons $\ddot{I}{€}^0$, $\hat{I}\cdot$, $\hat{I}›$, $K_s^0$, $\ddot{I}‰$ allows a surprisingly good description of their abundances with parameters $T_{chem}=(99\pm 11)$ MeV and $\hat{I}{¼}_b=(619\pm 34)$ MeV, which fits well in the chemical freeze-out systematics found in heavy-ion collisions. In supplement we reanalyze our previous HADES data from Ar+KCl collisions at $\sqrt{s_{NN}}$= 2.6 GeV with an updated version of the statistical model. We address equilibration in heavy-ion collisions by testing two aspects: the description of yields and the regularity of freeze-out parameters from a statistical model fit. Special emphasis is put on feed-down contributions from higher-lying resonance states which have been proposed to explain the experimentally observed $\hat{I}{ž}^{-}$ excess present in both data samples.