2 00 5 Can dissipation prevent explosive decomposition in high - energy heavy ion collisions ?

We discuss the role of dissipation in the explosive spinodal decomposition scenario of hadron production during the chiral transition after a high-energy heavy ion collision. We use a Langevin description inspired by microscopic nonequilibrium field theory results to perform real-time lattice simulations of the behavior of the chiral fields. We show that the effect of dissipation can be dramatic. Analytic results for the short-time dynamics are also presented. Lattice QCD results [1] suggest that strongly interacting matter at sufficiently high temperature undergoes a phase transition (or a crossover) to a deconfined quark-gluon plasma (QGP). Despite the difficulties in identifying clear signatures of a phase transition in ultrarelativistic heavy ion collisions, recent data from the experiments at BNL-RHIC clearly point to the observation of a new state of matter [2]. Depending on the nature of the QCD phase transition, the process of phase conversion in the expanding QGP generated in a high-energy heavy-ion collision may proceed in a number of different ways. In general, there is a competition between the mechanisms of nucleation and spinodal decomposition [3]. Results from CERN-SPS and BNL-RHIC feature what has been called sudden hadronization [4] or explosive behavior [5] in the hadronization process of the expanding QGP and seem to favor a fast (explosive) spinodal decomposition.