New results on mesonic weak decay of p-shell Lambda-hypernuclei

Abstract The FINUDA experiment performed a systematic study of the charged mesonic weak decay channel of p -shell Λ -hypernuclei. Negatively charged pion spectra from mesonic decay were measured with magnetic analysis for the first time for 7 Λ Li, 9 Λ Be, 11 Λ B and 15 Λ N. The shape of the π − spectra was interpreted through a comparison with pion distorted wave calculations that take into account the structure of both hypernucleus and daughter nucleus. Branching ratios Γ π − / Γ tot were derived from the measured spectra and converted to π − decay rates Γ π − by means of known or extrapolated total decay widths Γ tot of p -shell Λ -hypernuclei. Based on these measurements, the spin-parity assignment 1 / 2 + for 7 Λ Li and 5 / 2 + for 11 Λ B ground-state are confirmed and a spin-parity 3 / 2 + for 15 Λ N ground-state is assigned for the first time.