Status of the $${\mathbf {\Lambda (1405)}}$$ Λ ( 1405 )

Abstract

I give an overview of the current status of the lowest s-wave baryon resonance in the strangeness ( $$S=-1$$ ) channel, the $$\varLambda (1405)$$ . Recent results from Lattice QCD calculations and new high-precision data from photoproduction experiments are highlighted in this talk. On the theoretical side various directions have been explored over the last two decades on the basis of coupled-channel chiral unitary models. New photoproduction data can be used to reduce statistical uncertainty of the predictions of such models. As for the systematic uncertainties, a recent comparative analysis of modern approaches exhibits many similarities but also large ambiguities in some of the predicted properties of the antikaon-nucleon scattering amplitudes. Some possible ways to reduce such a model dependence are discussed at the end of this manuscript.