Double-ionization fraction of the Glauber cross sections for proton and helium collisions

Differential cross sections for single and double ionization for p+He collisions at 0.3, 0.7, and 1 MeV are calculated using the Glauber approximation. The angular dependence of the fraction of double ionization shows a sharp peak at a scattering angle of 0.8 mrad, which is slightly smaller than the experimental finding. The peak values decrease slowly with increasing collision energies, in accordance with the experiment, but the absolute values are about twice as large. The analysis of the present result shows that the peak of the fraction is caused mainly by the structure of the single-ionization cross section rather than the double-ionization cross section