Effects of short range Delta N interaction on observables of the pi NN system.

Abstract

The inadequacy of standard few-body approaches in describing the {pi}{ital NN} system has motivated searches for the responsible missing mechanism. In the case of {pi}{ital d} scattering, it has recently been asserted that an additional short range {Delta}{ital N} interaction can account for essentially all the discrepancies between a few-body calculation and experimental data. This conclusion, however, has been based on calculations where a phenomenological {Delta}{ital N} interaction is added only in Born term to background few-body amplitudes. In the present work we investigate the effect of including such a {Delta}{ital N} interaction to all orders within a unitary few-body calculation of the {pi}{ital NN} system. Besides testing the validity of adding the {Delta}{ital N} interaction in Born term in {pi}{ital d} scattering, our fully coupled approach also enables us to see the influence of the same {Delta}{ital N} interaction on the processes {ital NN}{r arrow}{pi}{ital d} and {ital NN}{r arrow}{ital NN}. For {pi}{ital d} elastic scattering, we find that the higher order {Delta}{ital N} interaction terms can have as much influence on {pi}{ital d} observables as the lowest order contribution alone. Moreover, we find that the higher order contributions tend to cancel the effect obtained by adding the {Delta}{italmore » N} interaction in Born term only. The effect of the same {Delta}{ital N} interaction on {ital NN}{r arrow}{pi}{ital d} and {ital NN}{r arrow}{ital NN} appears to be as significant as in {pi}{ital d}{r arrow}{pi}{ital d}, suggesting that future investigations of the short range {Delta}{ital N} interaction should be done in the context of the fully coupled {pi}{ital NN} system.« less