4PI data of relativistic nuclear collisions

The Plastic Ball, the first electronic nonmagnetic particle identifying four-pi spectrometer, was used to evaluate complete events of relativistic nuclear collisions. The large multiplicities of events and the electronic data acquisition and processing system gave a very large amount of data. Computer selection and further processing led to reliable evaluated results. In the present paper a part of them, concerning stopping and thermalization in relativistic heavy ion collisions are reported. Some considerations on composite particle and entropy production in connection with a possible phase transition in nuclear matter are described. (D.Gy.)