Transverse energy and multiplicity from heavy ion collisions at 200 A GeV

The successful acceleration of light ions at the CERN SPS and at the Brookhaven AGS opened the exciting field of ultra-relativistic heavy ion collisions for systematic studies. The first experiments were designed mainly to survey the reactions and to establish the essential features of the collisions. In this paper results from the WA80 experiment on transverse energy and charged particle multiplicity are reported. These two quantities are determined by most of the experiments and can be used to characterize the events. Large multiplicities and large transverse energies are correlated with violet collisions or with small impact parameters. In addition, an estimate of the energy density reached in the collision can be derived from those two measurements. One would like to know if the energy density necessary for the transition to the quark gluon plasma has been reached. The results of the first round of experiments with oxygen ions at 60 and 200 GeV per nucleon are collected in the proceedings of the Quark Matter 88 Conference. Some of these results are summarized here together with new results on multiplicity fluctuations