Measurements of the Interaction of 95-Mev Protons withHe4

Abstract

Elastic and inelastic scattering and the ($p, d$) "deuteron pickup" process have been studied using a proton beam of energy about 95 Mev incident on a liquid helium target. The elastic scattering shows a nuclear Coulomb interference dip at 9\ifmmode^\circ\else\textdegree\fi{}, a slight diffraction-type minimum at about 57\ifmmode^\circ\else\textdegree\fi{}, and a deep minimum, approximately ${10}^{\ensuremath{-}29}$ ${\mathrm{cm}}^{2}$/sterad at 135\ifmmode^\circ\else\textdegree\fi{}. (All angles and cross sections are in the center-of-mass system.) Inelastic scattering spectra were obtained at laboratory angles of 10\ifmmode^\circ\else\textdegree\fi{}, 15\ifmmode^\circ\else\textdegree\fi{}, and 30\ifmmode^\circ\else\textdegree\fi{}. These spectra are characterized by broad peaks, roughly 10-Mev wide, centered around an energy about 6 Mev below the upper kinematical limit for inelastic scattering. Their interpretation is discussed qualitatively both in terms of quasi-elastic nucleon-nucleon scattering and in terms of strong interaction between parts of the dissociated $\ensuremath{\alpha}$ particle in virtual or continuum states. A minimum was observed in the ${\mathrm{He}}^{4}(p, d){\mathrm{He}}^{3}$ differential cross section at about 29\ifmmode^\circ\else\textdegree\fi{}. Analysis of the ($p, d$) data at 95 Mev and 32 Mev in the "transparent nucleus" Born approximation yielded inconsistent results; presumably this inconsistency is due to the failure of the model at the lower energy due to the tightly bound structure of ${\mathrm{He}}^{4}$.