On the structure in the ΛN cross section at the ΣN threshold * *Supported in part by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) and the NSFC through the funds provided to the Sino-German Collaborative Research Center CRC 110 “Symmetries and the Emergence of Structure in QCD” (DFG Project-ID 196253076 - TRR 110, Grant No. 12070131001) and by the EU

Abstract

The complexity of threshold phenomena is exemplified on a prominent and long-known case - the structure in the cross section (invariant mass spectrum) at the opening of the channel. The mass splitting between the baryons together with the angular momentum coupling in the - partial wave imply that, in principle, up to six channels are involved. Utilizing hyperon-nucleon potentials that provide an excellent description of the available low-energy and scattering data, the shape of the resulting cross section is discussed and the poles near the threshold are determined. Evidence for a strangeness dibaryon is provided, in the form of a (unstable) bound state in the vicinity of the threshold. Predictions for level shifts and widths of atomic states are given.