The energy spacing between the spin-doublet bound state of HeΛ4(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 He4(K-,π-)HeΛ4 reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus HΛ4, the present result clearly indicates the existence of charge symmetry breaking (CSB) in ΛN interaction. By combining the energy spacings with the known ground-state binding energies, it is also found that the CSB effect is large in the 0+ ground state but is vanishingly small in the 1+ excited state, demonstrating that the ΛN CSB interaction has spin dependence.

Original languageEnglish
Article number222501
JournalPhysical Review Letters
Issue number22
Publication statusPublished - 2015 Nov 24


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