“Quantum” molecular dynamics-a dynamical microscopic n-body approach to investigate fragment formation and the nuclear equation of state in heavy ion collisions
The quantum molecular dynamics approach, an n-body theory to describe heavy ion reactions between 100 MeV/n and 2 GeV/n is reviewed. We start out with a survey of the present status of nuclear matter calculations and of kinetic theories as far as they are of importance for our approach. We then present a detailed derivation of the quantum molecular dynamics equation, discuss the various approximations necessary to derive this equation and to make actual calculations feasible. The calculations presented aim at the solution of two of the most interesting questions of contemporary heavy ion physics: What causes a nucleus to fragment into many heavy pieces, and can we determine the nuclear equation of state from heavy ion reactions? We first make detailed comparisons with a multitude of experimental data, which yield unexpectedly good agreement. We then proceed to detailed investigations of these questions. We find that fragmentation at these energies is triggered by the density wave caused by the projectile while travelling through the target. We reproduce the “squeeze out” and the “bounce off” predicted by hydrodynamical calculations and recently seen in experiment. Thus there is hope that the nuclear equation of state can be extracted from heavy ion experiments. However, very careful multiparameter experiments are necessary before one can achieve this goal.