Gamma-ray spectroscopy of hypernuclei: Recent results and future plans

A series of hypernuclear γ-ray spectroscopy experiments using a germanium detector array, Hyperball, have accumulated precise data on various p-shell Λ hypernuclei. Recently, ¹²_ΛC and ¹¹_ΛB were studied at KEK using the (π⁺, K⁺ γ) reaction, and a transition from a directly-populated spin-flip state, ¹⁶_ΛO(2^-), was observed in BNL E930 data. It is discussed whether the spin-dependent ΛN interaction parameters determined from previous experiments can consistently explain other γ spectroscopy data. At the J-PARC facility, further hypernuclear γ-ray spectroscopy experiments are planned, particularly to measure the g factor of a Λ in a nucleus from a spin-flip B (M 1) value and to investigate the ΛN interaction more in detail.