High-resolution γ-ray spectroscopy of hyperfragments produced by stopped reactions

We performed an experiment to measure γ rays of hyperfragments produced by stopped K − reactions on light ( A ⩽ 12 ) targets (KEK-PS E509). We clearly observed an E2 transition ( 5 / 2 + → 1 / 2 + ) in 7ΛLi with 10B, 11B and 12C targets and obtained the γ-ray intensity to be ( 7.5 ± 1.6 ) × 10 −4 per stopped K − for 10B target. In addition, a candidate for a new hypernuclear γ ray was observed. These results show that this method is quite suitable for the systematic study of hypernuclei.