2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/82063We compare the most used approximations to calculate the contribution from pion re-scattering mechanisms to pion production from proton-proton scattering, near threshold. Our calculation employs a pseudo-vector coupling for the pi NN vertex and realistic amplitudes for the pi N re-scattering and the NN transitions.3 pages, 1 figure. To be published in the proceedings of the 17th International IUPAP Conference on Few-body Problems in Physics, June 5-10, 2003, Durham, North Carolina, USANuclear Theorytext