Low lying S=−1 excited baryons and chiral symmetry

The s-wave meson–baryon interaction in the S=−1 sector is studied by means of coupled-channels, using the lowest-order chiral Lagrangian and the N/D method to implement unitarity. The loops are regularized using dimensional renormalization. In addition to the previously studied Λ(1405), employing this chiral approach leads to the dynamical generation of two more s-wave hyperon resonances, the Λ(1670) and Σ(1620) states. We make comparisons with experimental data and look for poles in the complex plane obtaining the couplings of the resonances to the different final states. This allows us to identify the Λ(1405) and the Λ(1670) resonances with K̄N and KΞ quasibound states, respectively.