Study of Λ-Hypernuclei with Stopped K− Reaction

Abstract

We summarize studies of Λ hypernuclei with stopped K− reaction carried out at KEK. The π− momentum spectra in the (stopped K−, π−) reaction were measured with light nuclear targets (4He, 7Li, 9Be, 12C and 16O). The ground and excited states of Λ4He, Λ12C and Λ16O were identified and their formation probabilities were measured. The branching ratios of π0-mesonic decay of Λ4He, Λ11B and Λ12C were measured for the first time with π0 coincidence. The lifetime of Λ4H was also determined with an improved accuracy. The π− peak intensity from Λ4H→4He+π− decay gave the Λ4H formation probabilities on these targets, where Λ4H is produced as hyperfragment except for the case of the 4He target. Concerning the formation mechanism of hyperfragments and their application to hypernuclear γ-ray spectroscopy, the running experiments and future prospects are also described.