Measurement of the proton spectra from non-mesonic weak decay of 5ΛHe, 7ΛLi and 12ΛC

Abstract The results of a measurement of the proton spectra following the non-mesonic weak decay of 5 Λ He, 7 Λ Li and 12 Λ C are presented and discussed. The experiment was performed at the ( e + e − ) collider DAΦNE at Laboratori Nazionale di Frascati of INFN. It is the first measurement for 7 Λ Li, and for all the spectra the lower limit on the energy of the protons is 15 MeV, never reached before. All the spectra show a similar shape, namely a peak at around 80 MeV as expected for the free Λ p → n p weak reaction, with a low energy rise that should be due to final state interactions and/or two-nucleon induced weak processes. The decay spectrum of 5 Λ He is somehow similar to the ones reported by previous measurements and theoretical calculations, but the same does not happen for the 12 Λ C one.