Gamma spectroscopy of hypernuclei: a decade of Hyperball project and future plans at J-PARC

Since 1998 we have conducted the project of precision hypernuclear γ-ray spectroscopy using the Ge detector array, Hyperball, and revealed precise level schemes of various p-shell hypernuclei. In the latest experiment at KEK (E566), the ground-state spacing of and hypernuclei have been obtained using the reaction. The accumulated data on the p-shell hypernuclear level energies allow us to establish all of the four strengths of the ΛN spin-dependent interactions and to discuss the ΛN-ΣN coupling force in a nucleus. Further experiments at J-PARC are being prepared, where we tackle new experimental challenges such as a precise measurement of the Λ-spin-flip B(M1) values and exploration of sd-shell hypernuclei.