Production of heavy fragments in the fission mass region in 12C+U, Bi, Au and Ag reactions at 26.5Â GeV

Formation of heavy fragments in the fission mass region in the interaction of 26.5 GeV C12 with U, Bi, Au and Ag is studied using a sandwich configuration of the Makrofol polycarbonate track detector. Events in which at least one heavy fragment in the fission mass region is detected are analyzed. Fragments produced in these events are identified and an event-by-event model-free analysis is performed in order to separate different production mechanisms. We have identified the events produced in fission, deep spallation and fragmentation processes. The cross sections and experimental features are determined for these reaction mechanisms, and their variations as a function of the target mass have been investigated. The results show that in the interactions of C12 with U the dominant process is fission, while in the interactions of C12 with lighter target nuclei the dominant processes are deep spallation and fragmentation.