Entropy production and collision number in dynamics process of heavy ion collisions and properties of hot nuclei

To study the properties of hot nucleus, entropy production should be chosen, which is sensitive to the early process of the reaction and unchanged by later expansion and coiling. The BUU equation with momentum dependence potential and two-body collision number for the reaction 40Ca + 40Ca with beam energy regions from 200 to 800 MeV/u and impact parameters b = 1,3,5 fm under four conditions which include free nucleon-nucleon collision and separately with momentum dependence potential (FP), hard potential (FH), soft potential (FS); momentum dependence potential and nucleon-nucleon collisions in the medium (MP)