Neutron and proton energy spectra from the non-mesonic weak decays of [formula omitted] and [formula omitted

Abstract

We have simultaneously measured the energy spectra of neutrons and protons emitted in the non-mesonic weak decays of HeΛ5 and CΛ12 hypernuclei produced via the (π+,K+) reaction with much higher statistics than those of previous experiments. The neutron-to-proton yield ratios for both hypernuclei at a high energy threshold (60 MeV) were approximately equal to two, which suggests that the ratio of the neutron- and proton-induced decay channels, Γn(Λn→nn)/Γp(Λp→np), is about 0.5. In the neutron energy spectra, we found that the yield of the low-energy component is unexpectedly large, even for HeΛ5.