Antikaon–nucleon interaction and Λ(1405) in chiral SU(3) dynamics

The properties of the Λ(1405)Λ(1405) resonance are key ingredients for determining the antikaon–nucleon interaction in strangeness nuclear physics, and the novel internal structure of the Λ(1405)Λ(1405) is of great interest in hadron physics, as a prototype case of a baryon that does not fit into the simple three-quark picture. We show that a quantitative description of the antikaon–nucleon interaction with the Λ(1405)Λ(1405) is achieved in the framework of chiral SU(3) dynamics, with the help of recent experimental progress. Further constraints on the K¯N subthreshold interaction are provided by analyzing π  Σ spectra in various processes, such as the K−d→πΣnK−d→πΣn reaction and the Λc→ππΣΛc→ππΣ decay. The structure of the Λ(1405)Λ(1405) is found to be dominated by an antikaon–nucleon molecular configuration, based on its wavefunction derived from a realistic K¯N potential and the compositeness criteria from a model-independent weak-binding relation.