## On chemical equilibrium in nuclear collisions

• The data on average hadron multiplicities in central A+A collisions measured at CERN SPS are analysed with the ideal hadron gas model. It is shown that the full chemical equilibrium version of the model fails to describe the experimental results. The agreement of the data with the off-equilibrium version allowing for partial strangeness saturation is significantly better. The freeze-out temperature of about 180 MeV seems to be independent of the system size (from S+S to Pb+Pb) and in agreement with that extracted in e+e-, pp and p{\bar p} collisions. The strangeness suppression is discussed at both hadron and valence quark level. It is found that the hadronic strangeness saturation factor gamma_S increases from about 0.45 for pp interactions to about 0.7 for central A+A collisions with no significant change from S+S to Pb+Pb collisions. The quark strangeness suppression factor lambda_S is found to be about 0.2 for elementary collisions and about 0.4 for heavy ion collisions independently of collision energy and type of colliding system

Author: Francesco BecattiniORCiDGND, Marek GaździckiORCiD, Josef Sollfrank urn:nbn:de:hebis:30-17142 https://doi.org/10.48550/arXiv.hep-ph/9710529 http://arxiv.org/abs/hep-ph/9710529 Report number: DFF 292/10/1997, IKF-HENPG/4-97, BI-TP 97/42 IKF–HENPG (4–97) Frankfurt am Main Working Paper English 2005/09/30 1997 Universitätsbibliothek Johann Christian Senckenberg 2005/09/30 24 später: The European Physical Journal C - Particles and Fields, 5.1998, S. 143- 153 Eur.Phys.J. C5 (1998), http://arxiv.org/abs/hep-ph/9710529 185284175 Physik / Physik 5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik Universitätspublikationen Deutsches Urheberrecht