MULTIFRAGMENTATION OF TOROIDAL AND BUBBLE NUCLEI WITHIN THE BUU APPROACH

Multifragmentation, following the formation of toroidal and bubble nuclei, is observed with an improved Boltzmann-Uehling-Uhlenbeck (BUU) model for central Mo-92 + Mo-92 collisions. With a stiff equation of state, simultaneous explosion into several nearly-equal fragments (NEFs) in a ring-like manner occurs due to the formation of metastable toroidal nuclei. In contrast, with a soft equation of state, simultaneous explosion into several NEFs in a volume-like manner occurs due to the formation of metastable bubble nuclei. Guided by our BUU model, we propose two signatures: (1) because of the geometries of bubbles and toroids and because of the cold breakup at low temperatures, we predict enhanced cross sections for NEFs at small center-of-mass energies. (2) the coplanarity of these NEFs could carry important information concerning the geometry of the sources. This, in turn, could provide information about the stiffness of the equation of state. Finally, the dependence of these two predictions on the number of test particles, impact parameters, and the initial random seeds are assessed.