On the nature of isovector exchange in the reaction NN - NN π by comparison with elastic π N scattering

The results of a cross channel isospin amplitude analysis of the reactionNN-NNπ concerning isovector exchange cross-sections for production ofNπ systems of isospin 1/2 and 3/2, σ 1/2 1 and σ 3/2 1 , respectively, have been compared with πN elastic-scattering data. No off-mass-shell corrections are made. We normalize the elastic data to the σ 3/2 1 crosssection in the Δ(1236) mass region and find that in the energy range (7÷20) GeV pion exchange gives an important contribution to σ 1/2 1 . The relative contribution seems to decrease with increasing energy.