Gamma-ray Spectroscopy of Single Λ-hypernuclei at J-PARC: Results and Perspective

Experimental results from the J-PARC E13 experiments are summarized. A new experimental set up of E13 has established a platform for the future gamma-ray hypernuclear spectroscopy at J-PARC using kaon beams. New gamma rays are identified in He-4(Lambda) and F-19(Lambda). The energy of 1.406 MeV for the He-4(Lambda)(1(+)-> 0(+)) transition confirmed a sizable effect of Charge Symmetry Breaking (CSB) in Lambda N interaction in the A=4 hypernuclear system. The identification of four gamma rays in F-19(Lambda) is made for the first time in sd shell hypernuclei. Especially, energy spacing of the ground state doublet is found to be 315.5 keV. A good agreement with two theoretical calculations suggests that the theoretical formalism used in p shell hypernuclei is also applicable to heavier hypernuclei. Lastly, an overview of the future J-PARC E63 experiment is given.