
The swave mesonbaryon scattering is analyzed for the strangeness S=1 and isospin I=0 sector in a BetheSalpeter coupled channel formalism incorporating chiral symmetry. Four channels have been considered: piSigma, (K) over barN, etaLambda, and KXi. The required input to solve the BetheSalpeter equation is taken from lowest order chiral perturbation theory in a relativistic formalism. There appear undetermined low energy constants, as a consequence of the renormalization of the amplitudes, which are obtained from fits to the piSigma>piSigma mass spectrum, to the elastic (K) over barN>(K) over barN and (K) over barN>piSigma t matrices and to the K()p>etaLambda cross section data. The position and residues of the complex poles in the second Riemann sheet of the scattering amplitude determine the masses, widths, and branching ratios of the S01 resonances Lambda(1405) and Lambda(1670), in reasonable agreement with experiment. A good overall description of the data, from the piSigma threshold up to 1.75 GeV, is achieved despite the fact that threebody channels have not been explicitly included.
