Amplitudes and model for πn backward scattering at 6 GeVc

Using reasonable assumptions concerning the s-channel helicity-nonflip amplitude M++32 of isospin 32 in the u channel and the helicity-flip amplitude M+-12, we extract from the data at 6 GeVc on πN backward scattering the remaining amplitudes. We find that the isospin-32 amplitudes can be described in a Regge-pole model with absorption. A description of M12 amplitudes is given, using degenerate Nα and Nγ trajectories. The Nγ couplings are found to be fairly important, especially in the M++12 amplitude which then has to be strongly absorbed.