Excitation function for [sup 4]He([pi][sup +],[ital pp])[sup 2]H two-nucleon absorption across the [Delta] resonance

Angular distributions and total cross sections for the [sup 4]He([pi][sup +],[ital pp])[sup 2]H reaction have been measured with small relative uncertainties at incident energies of [ital T][sub [pi]][sup +]=64, 87, 114, 162, 217, 278, and 327 MeV. The results strongly support the quasideuteron absorption model for pion absorption on two nucleons, which is found to contribute only [approx]50% to the total absorption cross section near the [Delta] resonance. All essential reaction channels of pion absorption near the [Delta] resonance on heavier nuclei seem to be present in [sup 4]He, but not in [sup 3]He. Any nuclear-density-related increase of pion absorption in [sup 4]He relative to [sup 2]H is [lt]50% and no binding energy effect is found.