Matter with strangeness Original Research Article

A recent experimental progress of strangeness nuclear physics is reviewed from viewpoint of hyperon-nucleon (YN) and hyperon-hyperon (YY) interactions. Detailed level structure of Λ hypernuclei has been studied by γ-ray spectroscopy technique using a germanium detector array as well as an NaI counter array, which determined the strengths of the ΛN spin-spin and spin-orbit interactions. In the emulsion-counter hybrid experiment, a double Λ hypernucleus ΛΛ6 He was observed and the strength of the ΛΛ interaction was unambiguously derived. As for the ΣN interaction, a recent 28Si(π−, K+) spectrum suggests a strongly repulsive Σ-nucleus potential, while the spin-orbit force of Σ is being studied by a Σp scattering experiment.