Structure of the Λ(1405) and the K-d→π Σn reaction

The Λ(1405) resonance production reaction is investigated within the framework of the coupled-channels Alt-Grassberger-Sandhas (AGS) equations. We perform full three-body calculations for the K̄NN-πYN amplitudes on the physical real energy axis and investigate how the signature of the Λ(1405) appears in the cross sections of the K-d→πΣn reactions, also in view of the planned E31 experiment at J-PARC. Two types of meson-baryon interaction models are considered: an energy-dependent interaction based on chiral SU(3) effective field theory, and an energy-independent version that has been used repeatedly in phenomenological approaches. These two models have different off-shell properties that imply correspondingly different behavior in the three-body system. We investigate how these features show up in differential cross sections of K-d→πΣn reactions. Characteristic patterns distinguishing between the two models are found in the invariant mass spectrum of the final πΣ state. The K-d→πΣn reaction, with different (π±Σ and π0Σ0) charge combinations in the final state, is thus demonstrated to be a useful tool for investigating the subthreshold behavior of the K̄N interaction.