Heavy ion reactions at the BEVALAC

The progress in understanding reactions with heavy ions at relativistic energies in recent years is reviewed. A strong guideline for the experimental program has been the desire to produce dense nuclear matter in the laboratory. The insensitivity of single particle inclusive measurements to nuclear compression has led to experiments using 4π detectors in order to study global event parameters. A collective emission pattern is observed in accordance with nuclear fluid dynamic predictions. The application of microscopic non-equilibrium models to describe experimental observables like collective flow, rapidity distributions, fragment ratios and particle production has revealed the importance of considering the many-body properties of the nucleon-nucleon interaction, so that the nuclear dynamics can be understood which masks the properties of cold dense nuclear matter. (orig.)