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

Agnello, M.; Andronenkov, A.; Beer, G.; Benussi, L.; Bertani, M.; Bhang, H. C.; Bonomi, Germano; Botta, E.; Bregant, M.; Bressani, T.; Bufalino, S.; Busso, L.; Calvo, D.; Camerini, P.; Dalena, B.; De Mori, F.; D'Erasmo, G.; Fabbri, F. L.; Feliciello, A.; Filippi, A.; Fiore, E. M.; Fontana, A.; Fujioka, H.; Genova, P.; Gianotti, P.; Grion, N.; Hartmann, O.; Kang, B.; Lenti, V.; Lucherini, V.; Marcello, S.; Maruta, T.; Mirfakhrai, N.; Montagna, P.; Morra, O.; Nagae, T.; Nakajima, D.; Outa, H.; Pace, E.; Palomba, M.; Pantaleo, A.; Panzarasa, A.; Paticchio, V.; Piano, S.; Pompili, F.; Rui, R.; Sanchez Lorente, A.; Sekimoto, M.; Simonetti, G.; Toyoda, A.; Wheadon, R.; Zenoni, Aldo; Gal, A.

doi:10.1016/j.physletb.2009.09.061

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.