Breakup reactions of Li-11 within a three-body model

We use a three-body model to investigate breakup reactions of Li-11 (n + n + Li-9) on a light target. The interaction parameters are constrained by kn own properties of the two-body subsystems, the Li-11 binding energy and fra gmentation data. The remaining degrees of freedom are discussed. The projec tile-target interactions are described by phenomenological optical potentia ls. The model predicts dependence on beam energy and target, differences be tween longitudinal and transverse momentum distributions, and provides abso lute values for all computed differential cross sections. We give an almost complete series of observables and compare with corresponding measurements . Remarkably good agreement is obtained. The relative neutron-Li-9 p-wave c ontent is about 40%. A p-resonance, consistent with measurements at about 0 .5 MeV of width about 0.4 MeV, seems to be necessary. The widths of the mom entum distributions are insensitive to target and beam energy with a tenden cy to increase towards lower energies. The transverse momentum distribution s are broader than the longitudinal ones due to the diffraction process. Th e absolute values of the cross sections follow the neutron-target cross sec tions and increase strongly for beam energies decreasing below 100 MeV/nucl eon. [S0556-2813(99)02103-2].