K-matrix fits to πN-->Nπ and πN-->Nππ in the resonance region s=1.3 to 2.0 GeV

Starting with partial-wave amplitudes for πN-->Nπ and πN-->several isobar-model states of Nππ, we are able to apply the constraint of unitarity (using the K matrix). This permits the removal of the overall phase ambiguity of the isobar amplitudes at each energy. The K-matrix fits generate a smooth prescription for the T-matrix amplitudes, enabling us to search the complex energy plane for poles. The uniqueness of these poles is demonstrated by doing Breit-Wigner refits to the fitted T-matrix amplitudes. The success of the refits and the obvious interpretation justifies a simple determination of coupling signs for which there can be checks with theory.