INVARIANT MASS-SPECTRUM AND ALPHA-N CORRELATION-FUNCTION STUDIED IN THE FRAGMENTATION OF HE-6 ON A CARBON TARGET

Momentum distributions and invariant mass spectra from the breakup of He-6 ions with an energy of 240 MeV/u interacting with a carbon target have been studied. The data were used to extract information about th e reaction mechanism which is influenced by the structure of He-6. It is found that the dominant reaction mechanism is a two-step process: k nock out of one neutron followed by the decay of the He-5 resonance. T he shape of the (alpha+n) two-body invariant mass spectrum is interpre ted as mainly reflecting the 5He ground state which is a J(pi) = 3/2(- ) resonance. However, no evidence for correlations between cu particle s and neutrons is observed in the momentum widths of the distributions . It is demonstrated that a combined analysis of the two-body invarian t mass spectrum and an appropriate correlation function may be used to determine the properties of the intermediate resonance. (C) 1998 Else vier Science B.V.