Three- and four-body study of light hypernuclei and YN interaction

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[1] Theoretical prediction of B(E2) in hypemuclei.We calculated B(E2: 5/2^+_1 → 1/^+_1) in ^7_λLi and B(E2: 3^+_1→1^+_1) of the core nucleus ^6_λLi. From their comparison, we predicted that size of ^7_λLi is shrunk by 21% from the core nucleus. KEK-E419 experiment verified this prediction.[2] YN spin-orbit force and the level structure of ^9_λBe and ^13_λ3C.With the use of the two kinds of YN interactions we calculated energy splitting in the spin orbit doublet in ^9_λBe and ^13_λ3C. The quark-model-based interaction gave very small splitting, where as the meson-theory- based interaction gave substantially large splitting. Experiments at BNL reported a small splitting which agrees with the former case of our prediction.[3] Four-body study of ^4_λH and ^4_λHe.We performed, for the first time, four-body calculation of ^4_λH and ^4_λHe with the explicit use of the (3Ν+Λ) and (3Ν+Σ) channel. The ΛΝ-Σ coupling is treated accurately. We were able to explain the level structure of the hypemuclei and estimated the probability of the (3Ν+Σ) channel. It is 2% in the 0^+ state and 1% in the 1^+ state, but plays important role in making the states bound.[4] Spectroscopy of the double-Λ hypemuclei.We predicted the energy levels of the A=7-10 double-Λ hypemuclei with the use of the α+χ+Λ+Λ four-body model with χ= n,p,t,^3He,α. Our prediction for 2^+ state of ^<10>_<ΛΛ>Be was recently verified by the DEMACHI-YANAGI event in the KEK-E373 experiment.