Multiproton final states in positive pion absorption below the Δ(1232) resonance

Inclusive cross sections for positive pion absorption leading to final States including two or more protons have been measured with a large solid angle detector for incident pion energies from 30 to 135 MeV for targets with A = 2-208. The mass dependences for the inclusive (π⁺,2p), (π⁺,3p), and total absorption cross sections for multiproton final states were found to be proportional to Aⁿ with n ≈ 0.5. These cross sections also were observed to have an energy dependence at energies below 150 MeV reflective of the importance of the Δ(1232) resonance, similar to that observed for πd → >pp. The inclusive cross sections for (π⁺ ,4p) were found to be less than 10 mb for all targets at all energies. Estimates were also obtained for cross sections for pion absorption leading to 2p 1n and 3 p1n final states. Quasideuteron absorption contributions increase slowly with A, and the energy dependence of those contributions mirrors that for -π d→ pp. The data obtained here for multiproton final states indicate that a significant fraction of absorption events, increasing with A, most likely arises from final states containing fewer than two protons.