Fermi motion and off-shell effects in the reaction 3He(γ,π+)3H

The reaction 3He(γ,π+)3H is studied in the impulse approximation using realistic wave functions obtained as solutions of the Faddeev equations with the Reid soft core potential. The influence of Fermi motion on the resonance structure is treated exactly. The previously used assumption (k1) = Q/3, defining an average nucleon momentum proportional to the overall momentum transfer Q, is shown to be a good approximation over a large range of photon energies and momentum transfers. The dependence of the results on different off-shell prescriptions is investigated for two models of the elementary pion photoproduction amplitude. (orig.)