High-resolution γ-ray spectroscopy of hyperfragments produced by stopped K− 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.