Department of Physics, State University of New York, Stony Brook, NY 11794, USA
Department of Theoretical Physics, University of Oulu, Linnanmaa, 90570, Oulu 57, Finland
Abstract:
The contribution of A1 exchange to the nucleon-nucleon potential is studied in a broken chiral symmetric model. The A1 is treated as a finite-width resonance in the πρ s-wave. Connections between pseudoscalar and pseudovector pion-nucleon coupling in the underlying model lagrangian are studied in detail. It is found that large terms in the NN interaction arising from πρ exchange with pseudoscalar coupling are suppressed by interference with a1 exchange. With pseudovector coupling there is a suppression of the A1 exchange by the so-called “seagull” terms in πρ exchange which arise from gauge invariance. The suppression becomes an exact cancellation in the limit of infinite ρ and a1 masses and exact chiral symmetry. We found that inclusion of the a1 decay into the πρ state strongly modifies the a1] exchange potential, suppressing the tensor part but leaving the spin-spin part almost unchanged.