Dominance Of The 2-Nucleon Mechanism In O-16(Pi+,Pp) At 115 Mev

Singles O-16(pi+,p) and coincidence O-16(pi+,2p)N-14 measurements have been made at T(pi) = 115 MeV over an extended range of the phase space of the two final-state protons. The coincidence measurements have a missing-mass resolution of 4 MeV. The direct two-nucleon absorption cross section extracted from the data is 58 +/- 8 mb. After corrections for final-state interactions, it was found that the two-nucleon pi+ + np --> pp process accounts for about 76% of the total absorption cross section, and thus is the dominant absorption mechanism. Evidence for absorption on s-p pairs is seen as a broad bump near 32 MeV of excitation. At backward angles the inclusive O-16(pi+,p) spectra show a distinct absorption peak, an important feature not previously observed. Comparisons of distorted wave impulse approximation calculations to both the coincidence data and inclusive data are presented.