Quantum molecular dynamics — A model for nucleus-nucleus collisions from medium to high energies

Abstract

The thermalisation process in heavy ion collisions is investigated employing the Quantum Molecular Dynamics approach. The validity of thermodynamical quantities, e.g. density, temperature and pressure are discussed. The investigation of the local degree of equilibrium leads to a three component picture, where in addition to the projectile and target a “fireball” component is defined, which includes all those nucleons which have suffered at least one hard collision. Local equilibration is observed in all of those components at all times. The dynamical evolution of the reaction is dominated by the interaction of both the projectile and the target with this fireball component and not, as was assumed in the two fluid model, by the interaction of projectile and target with each other. The structure of the stress tensor can be cast in a Newtonian form only for low energies. Then the values of the shear viscosity are in agreement with those values used in present viscous hydrodynamical calculations.