PUB - Publikationen an der Universität Bielefeld

The relative multiplicities for hadron production in different high energy collisions are in general well described by an ideal gas of all hadronic resonances, except that under certain conditions, strange particle rates are systematically reduced. We show that the suppression factor gamma_s, accounting for reduced strange particle rates in pp, pA and AA collisions at different collision energies, becomes a universal function when expressed in terms of the initial entropy density s_0 or the initial temperature T of the produced thermal medium. It is found that gamma_s increases from about 0.5 to 1.0 in a narrow temperature range around the quark-hadron transition temperature T_c = 160 MeV. Strangeness suppression thus disappears with the onset of color deconfinement; subsequently, full equilibrium resonance gas behavior is attained.