MULTINUCLEON EFFECTS IN MUON-CAPTURE ON HE-3 AT HIGH-ENERGY TRANSFER

Energy spectra of both protons and deuterons emitted following the cap ture of negative muons by He-3 nuclei have been measured for energies above 15 MeV. A limited number of proton-neutron pairs emitted in coin cidence were also observed. A simple plane wave impulse approximation (PWIA) model calculation yields fair agreement with the measured proto n energy spectra, but underpredicts the measured rate of deuteron prod uction above our energy threshold by a large factor. A more sophistica ted PWIA calculation for the two-body breakup channel, based on a real istic three-body wave function for the initial state, is closer to the deuteron data at moderate energies, but still is significantly lower near the kinematic end point. The proton-neutron coincidence data also point to the presence of significant strength involving more than one nucleon in the capture process at high energy transfer. These results indicate that additional terms in the capture matrix element beyond t he impulse approximation contribution may be required to explain the e xperimental data. Specifically, the inclusion of nucleon-nucleon corre lations in the initial or final state and meson exchange current contr ibutions could bring calculations into better agreement with our data. A fully microscopic calculation would thus open the possibility for a quantitative test of multinucleon effects in the weak interaction.