Abstract
The present calculation, devoted to proton-4He elastic scattering at 800 MeV, is the first to achieve good agreement with experimental data for polarization P and spin rotation parameters Q, S, starting from an accurate knowledge of the basic nucleon-nucleon amplitudes. The authors have studied the influence of Delta propagation in the intermediate steps of multiple scattering and the phase variation of the nucleon-nucleon amplitudes with momentum transfer. Both effects play an important role. Their phase value confirms the positive one of Franco and Yin (1986). The Delta production is treated in the full generality of their 16 spin-independent amplitudes. General formulae are derived to test the N Delta elastic scattering within the nucleus.