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

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