On the pole content of coupled channels chiral approaches used for the K¯N system

Several theoretical groups describe the antikaon–nucleon interaction at low energies within approaches based on the chiral SU(3) dynamics and including next-to-leading order contributions. We present a comparative analysis of the pertinent models and discuss in detail their pole contents. It is demonstrated that the approaches lead to very different predictions for the K−pK−p amplitude extrapolated to subthreshold energies as well as for the K−nK−n amplitude. The origin of the poles generated by the models is traced to the so-called zero coupling limit, in which the inter-channel couplings are switched off. This provides new insights into the pole contents of the various approaches. In particular, different concepts of forming the Λ(1405)Λ(1405) resonance are revealed and constraints related to the appearance of such poles in a given approach are discussed.