Unitary model for meson-nucleon scattering

We extract nucleon resonance parameters from an effective Lagrangian model employing the K-matrix approximation. To this end we analyze simultaneously all available data for reactions involving the final states pi N, pi pi N, eta N, and K Lambda in the energy range m(N) + m(pi) less than or equal to root s less than or equal to 1.9 GeV. The background contributions are generated consistently from the relevant Feynman amplitudes, which significantly reduces the number of free parameters.The sensitivity of the parameters upon the pi N-partial-wave analysis and the details of the Lagrangians and form factors used are discussed.