Angular distributions of antiprotons elastically and inelastically scattered by helium

Abstract

Angular differential cross sections are calculated for antiprotons elastically and inelastically scattered by the helium atom. The elastic cross sections are calculated quantum mechanically using both the adiabatic potential and a phenomenological optical potential. The absorptive effects, taken into account by the optical potential, are found to significantly suppress large-angle elastic scattering. Inelastic scattering (excitation and ionization) is treated by the quasiclassical fermion molecular dynamics method. The inelastic scattering is largely in the backward direction at laboratory collision energies within $\ensuremath{\sim}30\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ of threshold, but moves to smaller angles as the energy increases.