New results on Mesonic Weak Decay of $p$-shell $\hat{I}›$-Hypernuclei

Abstract

The FINUDA experiment performed a systematic study of the charged mesonic weak decay channel of $p$-shell $\hat{I}›$-hypernuclei. Negatively charged pion spectra from mesonic decay were measured with magnetic analysis for the first time for ${}_{\hat{I}}^7›Li$, ${}_{\hat{I}}^9›Be$, ${}_{\hat{I}}^{11}›B$ and ${}_{\hat{I}}^{15}›N$. The shape of the $\ddot{I}{€}^{-}$ 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 $\hat{I}{“}_{\ddot{I}{€}^{-}}/\hat{I}{“}_{tot}$ were derived from the measured spectra and converted to $\ddot{I}{€}^{-}$ decay rates $\hat{I}{“}_{\ddot{I}{€}^{-}}$ by means of known or extrapolated total decay widths $\hat{I}{“}_{tot}$ of $p$-shell $\hat{I}›$-hypernuclei. Based on these measurements, the spin-parity assignment $1/2^{+}$ for ${}_{\hat{I}}^7›Li$ and $5/2^{+}$ for ${}_{\hat{I}}^{11}›B$ ground-state are confirmed and a spin-parity $3/2^{+}$ for ${}_{\hat{I}}^{15}›N$ ground-state is assigned for the first time.

14 pages, 5 figures