The energy spacing between the ground-state spin doublet of 4 Λ He(1 + ,0 + ) was determined to be 1406 ± 2 ± 2 keV, by measuring γ rays for the 1 + → 0 + transition with a high efficiency germanium detector array in coincidence with the 4 He(K − , π − ) 4Λ He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus 4 Λ H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in ΛN interaction. It is also found that the CSB effect is large in the 0 + ground state but is by one order of magnitude smaller in the 1 + excited state, demonstrating that the ΛN CSB interaction has spin dependence.

No abstract

No abstract

No abstract

1. Introduction. Whether there exist kaonic nuclei or not is a key issue to make our understandings on theKN interaction in vacuum and in nuclear medium. The information on theKN interaction has been obtained by analyzing low-energyKN scattering data and kaonic-atom X-ray data [1]. The recent measurement of the energy shift and width on kaonic-hydrogen X-ray in high precision by the SIDDHARTA group [2] has contributed a lot [3]. From the theoretical analyses by using these results, it is well known that theKN