ENERGY-DEPENDENCE OF THE HE-3(P,PI+)HE-4 AND HE-3(N,PI-)HE-4 REACTIONS

We examine in detail the energy dependence of the various components of a microscopic calculation of the 3He(p, π+)4He reaction from the near-threshold region (Tlabp = 178 MeV, Tc.m.π = 10.5 MeV) to an energy at which the Δ1232 resonance should clearly dominate the reaction mechanism (Tlabp = 325 MeV, Tc.m.π = 110 MeV) and demonstrate the sensitivity of the calculations to pion and proton distortions. The discrepancy in size between the calculated and measured cross sections at the lower energies (Tlabp = 178 and 200 MeV), persisting in two earlier publications, is found to disappear when Coulomb effects are properly taken into account. Our present calculations give a reasonably good description of the measured cross section and analyzing-power data at these lower energies and predict a smooth energy dependence of the cross section at the higher energies reflecting the increasing importance of the Δ-resonance. Calculations for the charge-symmetric 3H(n, π-)4He reaction are compared with existing cross-section data for the time-reversed 4He(π-, n)3H reaction at the higher energies using detailed balance, while differences between the 3He(p, π+)4He and 3H(n, π-)4He reactions due to Coulomb effects are investigated. © 1990.