Non-equilibrium fluid-dynamics in the early stage of ultrarelativistic heavy-ion collisions

To describe ultrarelativistic heavy-ion collisions we construct a three-fluid hydrodynamical model. In contrast to one-fluid hydrodynamics, it accounts for the finite stopping power of nuclear matter, i.e. for non-equilibrium effects in the early stage of the reaction. Within this model, we study baryon dynamics in the BNL-AGS energy range. For the system Au+Au we find that kinetic equilibrium between projectile and target nucleons is established only after a time t(cm)(cq) approximate to 5 fm/c similar or equal to 2R(Au)/(gamma cm). Observables that are sensitive to the early stage of the collision (like e.g. nucleon flow) therefore differ considerably from those calculated in the one-fluid model. (C) 1997 Elsevier Science B.V.