Optical-model partial-wave analyses ofp−He4elastic scattering

We have performed optical-model calculations using the Klein-Gordon and the Dirac equations for the 600 MeV $p-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ scattering experiments of Boschitz et al., and the 1050 MeV $p-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ scattering experiments of Baker et al. We have compared these analyses with our previous analysis of the 1000 MeV $p-{}_{}{}^4{}_{}{}^{}\mathrm{He}$ experiment of Palevsky et al. In comparing the results at the three energies we find that the experiments require a slightly energy-dependent optical potential rms radius. The average value is in good agreement with the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ matter radius obtained from electron scattering, and substantially smaller than the low energy ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ optical potential rms radius. On the other hand, the experiments require quite different values for the optical potential strength parameters.