Cross channel isospin amplitudes for 3.9 GeV/c π+-p → π(Nπ) compared with the predictions of a double exchange model☆

Abstract A cross-channel isospin analysis has been carried out on a prism plot separated sample of 3.9 GeV/ c π +- p → π (N π ) events. An enhancement is observed in the low (Nπ) invariant mass region for an I = 1 2 state of the Nπ system when the isospin for the cross channel is both I E = 0 and 1. These results and those of similar analyses at 8 and 16 GeV/ c are compared with the predictions of a double-exchange model and good agreement is obtained. Neither interpretation of this phenomenon as a resonance nor as a consequence of diffraction dissociation in the usual definition, non-resonating single pomeron exchange, explains all the features of the results.