Simple observables sensitive to the transition from sequential decay to simultaneous break-up of nuclear systems

The relative velocities and relative angles between massive fragments emitted in heavy-ion nuclear reactions have been studied as a tool to discriminate between two extreme break-up mechanisms in the intermediate energy regime. Considering a chain of sequential decays and a simultaneous break-up of an excited nuclear system, we show that the behaviour of the event distribution in the space of relative velocities and angles depends on the fragmentation mechanism, indicating the possibility of observing the transition from the binary-decay mechanism to the simultaneous cracking of nuclear systems.