The Interaction of 970 MeV Protons with Helium

The interaction of 970 MeV protons with helium has been studied with a high-pressure diffusion cloud chamber. From 642 events the total and absorption cross-sections were found to be 116 ± 17 mb and 93 ± 13 mb, respectively. These agree with values obtained by extrapolation of known cross-sections for more complex nuclei, and the results are interpreted in terms of the optical model of the nucleus. The angular distribution for elastic-scattering yields an α-particle radius of 1⋅8 x 10-13cm. Quasi-elastic proton-proton and proton-neutron scattering, and more particularly charged meson production, show that the α-particle has some individual particle characteristics. Meson reabsorption appears unimportant.