Competition between fusion-evaporation and multifragmentation in central collisions in 58Ni + 48Ca reaction at 25 AMeV

The experimental data concerning the 58Ni+48Ca reaction at Elab(Ni)=25A MeV, collected by the CHIMERA 4π device, have been analyzed in order to investigate the competition among different reaction mechanisms for central collisions in the Fermi energy domain. The method adopted to select such central collisions, by means of construction of the kinetic energy tensor and, consequently, the evaluation of the “flow angle” event by event is presented. Some global variables, able to characterize the pattern of central collisions, have been constructed, and the main features of the reaction products are analyzed in terms of some observable, like mass and velocity distributions, as well as their correlations. Much emphasis was devoted to the competition between fusion-evaporation processes with consequent identification of a heavy residue and multifragmentation of a well defined (if any) transient nuclear system formed in central collisions.