pp ↔ π+d process at low energy: interplay between s- and p-wave mechanisms

The large variety of experimental data around the pion-production threshold are compared with a meson-exchange isobar model which includes the pion-nucleon interaction in s- and p-waves. Theoretical results obtained with two different NN potentials (Bonn and Paris) indicate that the behavior of the excitation function at threshold is sensitive to the details of the NN correlations. The complete model presented, while developed originally to reproduce the reaction around the Δ resonance, is shown to describe well the integral (Coulomb-corrected) cross-section at threshold along with its angular distribution. At low energies the angular dependence of the analyzing power Ayo is well reproduced also. Finally, the energy dependence of the analyzing power for θ = 90 deg from threshold up to the Δ resonance is considered and discussed. (authors)