Role of direct mechanisms in large-angle production of. cap alpha. particles in interaction of fast hadrons with 1p-shell nuclei

A consistent theoretical approach is used to evaluate the contributions of the quasielastic-knockout and spectator mechanisms to invariant spectra of ..cap alpha.. particles emitted into large angles in proton, deuteron, and ..cap alpha..-particle interactions with 1p-shell nuclei at energies of several GeV/nucleon. The role of rescattering from the nucleons in the knocked-out fragment, the residual nucleus, and the incident particle is investigated. It is shown that for the quasielastic-knockout mechanism one can obtain a good description of the experimental spectra of fragments emitted into angles of about 90/sup 0/ with 20--60 MeV energies. At larger energies of the particle detected, the contribution of the mechanism is smaller but still appreciable (up to 10%) up to energies of the order 180 MeV.