Nucleon-nucleon coincidence measurement in the non-mesonic weak decay of (5)(Lambda) He and C-12(Lambda) hypernuclei

摘要

We have measured both yields of neutron-proton and neutron-neutron pairs emitted from the non-mesoriic weak decay process of He-5(Lambda) and C-12(Lambda) hypernuclei produced via the A A (pi(+),K+) reaction for the first time. We observed clean back-to-back correlation of the np- and nn-pairs in the coincidence spectra for both hypernuclei. The ratio of those back-to-back pair yields, N-nn/N-np, must be close to the ratio of neutron- and proton-induced decay widths of the decay, Gamma(n)(Lambda n -> nn)/Gamma(p)(Lambda p -> np). The obtained ratios for each hypernuclei support recent calculations based on short-range interactions.