Hadronization and Strangeness Production in a Chirally Symmetric   Nonequilibrium Model
  The expansion and hadronization of a quark meson plasma is studied using an effective chiral interaction Lagrangian. The particles we consider are light as well as strange quarks, which can form pions, kaons and eta mesons via collision processes. The transport equations for the system are solved using a QMD type algorithm. We find that in chemical equilibrium at high temperatures the strange quark mass is considerably higher than the strange current quark mass and becomes even higher if we assume an initial state free of strange quarks. This leads to a considerably higher production threshold. In contrast to simpler scenarios, like thermodynamics of free quarks with their bare mass, we observe that strangeness production in a plasma is hindered and not favoured. The different particle species created during the evolution become separated in coordinate as well as in momentum space. We observe, as at CERN experiments, a larger mean momentum of kaons as compared to pions. Thus the radial collective velocity may as well originate from a plasma expansion and not necessarily from a hadronic scenario. 
P. Rehberg and J. Aichelin