4He(p,2p)3H reaction at intermediate energies

The 4He(p,2p)3He reaction has been studied at 250, 350, and 500 MeV using coplanar symmetric and asymmetric geometries. The data are presented as energy-sharing spectra, coplanar symmetric angular distributions, and quasifree angular distributions. A comparison with distorted-wave impulse approximation calculations indicates reasonable agreement for small recoil momenta (q< or approx. =150 MeV/c). For larger recoil momenta, the distorted-wave impulse approximation calculations increasingly underestimate the data. The discrepancies are substantially reduced by inclusion of a spin-orbit term in the optical potential used to generate the distorted waves. Improvements of the single particle wave function for the struck nucleon influence the calculations to a lesser degree. The remaining discrepancies at large recoil momenta may, in part be ascribed to multiple scattering effects and exchange processes not included in the standard distorted-wave impulse approximation