X iv : h ep - p h / 94 11 34 6 v 1 2 1 N ov 1 99 4 Hadronic Matter with Internal Symmetries and its Consequences : An Expanding Hadronic Gas ∗ Ludwik Turko

We consider an ideal gas of massive hadrons in thermal and chemical equilibrium. The gas expands longitudinally in accordance with Bjorken law. Strangeness and baryon number conservation is taken into account. This gas has different features as compared to the pion gas. Let us consider a heavy ion collision which goes through the intermediate state of an hadronic matter being in the thermal and chemical equilibrium. This matter can be considered as a gas which expands longitudinally according to a hydrodynamical evolution. In the simplest case the hadronic matter is supposed to be made of non interacting massless pions [1]. However an assumption of a thermodynamical equilibrium leads to the conclusions that a system under consideration should consist of all species of hadrons allowed by conditions of the equilibrium. We are going to consider an ideal gas consisting of all species of hadrons up to Ω− baryon. These realistic hadrons need that conservation laws due to an internal symmetries should be taken into account. The aim of this talk is to present some of pecularities of this more realistic hadronic gas as compared to the simple pion gas. Some of these comparison were published before to study J/Ψ suppression patterns [2]. For an ideal hadron gas in thermal and chemical equilibrium, which consists of l species of particles, energy density ǫ, baryon number density nB, strangeness density nS and entropy density s read (h̄ = c = 1 always)