High Precision γ-ray Spectroscopy of \(_\Lambda ^4\textHe\) and \(_\Lambda ^19\textF\) at J-PARC

A new γ-ray spectroscopy experiment on 4 He and 19F via the (K−, π−) reaction (J-PARC E13 1st ΛΛ Part) is being prepared at the J-PARC hadron facility. The measurement will provide information on the degree of charge symmetry breaking effect in ΛN interaction and information on the effective ΛN spin-spin interaction in sd-shell hypernuclei. In May 2013, a commissioning beam time was used to check beam conditions and performance of individual detectors as well as the whole system. Production of Σ+ and 12C through the (K−,π−) reaction was performed with a CH2 target. A CF2 Λ target was also tried to test the system in the γ-(K−, π−) reaction coincidence mode.