First determination of the one-proton induced Non-Mesonic Weak Decay width of p-shell Λ-Hypernuclei

Abstract Previous studies of proton and neutron spectra from Non-Mesonic Weak Decay of eight Λ -Hypernuclei ( A = 5 – 16 ) have been revisited. New values of the ratio of the two-nucleon and the one-proton induced decay widths, Γ 2 N / Γ p , are obtained from single proton spectra, Γ 2 N / Γ p = 0.50 ± 0.24 , and from neutron and proton coincidence spectra, Γ 2 N / Γ p = 0.36 ± 0.14 stat − 0.04 sys + 0.05 sys , in full agreement with previously published ones. With these values, a method is developed to extract the one-proton induced decay width in units of the free Λ decay width, Γ p / Γ Λ , without resorting to Intra Nuclear Cascade models but by exploiting only experimental data, under the assumption of a linear dependence on A of the Final State Interaction contribution. This is the first systematic determination ever done and it agrees within the errors with recent theoretical calculations.