Reaction 58Ni(π+,pp) at Tπ+=160 MeV

Abstract

The reaction 58Ni(π+,pp) was studied with good energy resolution for an incident pion energy of 160 MeV. The angular correlation of the outgoing protons was measured for θlab=30°, 75°, and 130°. From these angular correlations the contribution from direct two-nucleon absorption was extracted. A Monte Carlo calculation modeling the absorption process in terms of initial-state scattering of the pion before absorption, two-nucleon absorption, and final-state scattering of the outgoing nucleons is compared to the data. We conclude that within this framework the two-nucleon mechanism can account for less than half of the total absorption cross section in 58Ni. We report results for the low-energy coincidence proton spectra (down to 5 MeV) which suggest that most of these protons come from evaporation. Angular correlation data for the reaction 58Ni(π-,pp) are also presented.