pi N --> eta N and eta N --> eta N partial wave T-matrices in a coupled, three channel model
The pi N --> eta N and eta N --> eta N partial wave T-matrices for the eight lowest partial waves have been obtained in a three coupled channel model with unitarity manifestly imposed. The two physical channels are pi_N and eta_N, and the third channel, pi_pi_N is an effective, but unphysical two body channel which represents all remaining processes. The pi_N elastic phase shifts and the weighted data base of the pi- p --> eta n total and differential cross sections are chosen as the input for the fitting procedure. A model containing a single resonance in each of the three partial waves that dominates the eta production at lower energies is compared with previous analyses, based on similar assumptions. A multiresonance coupled channel model is introduced which significantly improves the agreement with all input data. Our results are compared with a complementary multiresonance coupled channel analysis that is constrained with elastic and continuum production channels. The inclusion of the fourth P11 resonance in the 1440 - 2200 MeV region further improves the agreement between the analysis and the data.