Cross-section measurements and phase shift analysis ofp-He4elastic scattering in the energy range 20-55 MeV

Measurements have been made of the $p$+${}_{}{}^4{}_{}{}^{}\mathrm{He}$ elastic scattering angular distributions at $T=21.85, 23.90, 25.75, 28.10, 30.35, 32.15, 34.25, 36.90, 39.75, 42.45, 44.05, 44.95, \mathrm{and} 47.65$ MeV in the angular range $10°\lesssim {\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\lesssim 170°$. The data obtained have in general relative errors smaller than 2%, while the absolute scale of the measurements has an uncertainty of less than 2.5%. These data together with differential cross sections and analyzing power angular distributions selected from the literature, as well as total reaction cross section information have been subjected to a phase shift analysis. Up to 45 MeV a single, continuous solution could be determined using phase shifts up through $G$-waves. As in an earlier phase shift analysis the phase shifts exhibit a smooth variation with energy except for the well-known resonance region around 23.4 MeV. Above 45 MeV some improvement was obtained with the inclusion of a small $H$-wave contribution. New total reaction cross section data were employed as a constraint on the imaginary parts of the phase shifts. The new analysis corroborates an early finding that the inelasticity is mainly associated with the even partial waves.