New results on mesonic weak decay of p-shell Lambda-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 7ΛLi, 9ΛBe, 11ΛB and 15ΛN. The shape of the pi− 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 Γpi−/Γtot were derived from the measured spectra and converted to pi− decay rates Γpi− 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 7ΛLi and 5/2+ for 11ΛB ground-state are confirmed and a spin-parity 3/2+ for 15ΛN ground-state is assigned for the first time.