The reaction p+3He→π++4He

We study the observables of the reaction p+3He→π++4He at 800 MeV incident energy. The model consists of a two-step process, in which a Δ is produced in a first collision and then decays in the nuclear medium, the decay nucleon being captured by the target. The full spin-isospin structure of the production and decay amplitudes is taken into account. The complete amplitude contains rescattering contributions calculated approximately. We assume a similar form for NN, ΔN and πN elastic scattering amplitudes, retaining only a central and a spin-orbit component. The calculated differential cross section and the asymmetry are compared with experimental data. The results show that the proposed mechanism is in fact the dominant contribution. The asymmetry is fairly sensitive to the Δ-production amplitudes, in particular to the interference between the multiple π exchange and the ρ contributions. (author)