Equilibration Compression And Flow At The Bevalac

This paper presents data acquired in the past two years by the Streamer Chamber group and the Plastic Ball group. The paper presents evidence that at Bevalac energies, head-on nuclear collisions result in stopping; it presents evidence for collective flow of the interacting nuclei; it presents evidence that a substantial part of the energy is tied up in compressional energy at the high density phase of the collision; finally, it presents recent data concerning aspects of the collisions such as interaction volume, particle ratios and temperatures. At the meeting at Bielefeld two years ago, it was not possible to make definitive statements about most of these subjects: the progress in the intervening period has been remarkable. 17 references, 14 figures, 1 table.

Recent experimental results from 4.pi. detectors at the Bevalac are presented, with emphasis on the Plastic Ball. Heavy nuclei, in central collisions at Bevalac energies, stop in their center of mass producing a region of equilibrated, hot matter. Some of the energy is stored as potential energy of compression. At the same time the pressure builds up, producing a sidewise collective flow of nuclear matter. The system then expands until the density is reduced so that the chemical equilibria producing the light composite nuclei freeze-out, and then even further until the thermal two body interactions freeze-out. Each of these points are discussed. 9 references.