This letter is concerned with the study of the $K^-_{stop}Arightarrow pi^pmSigma^mp A$ reaction in p-shell nuclei, i.e., $^{6,7}Li$, $^9Be$, $^{13}C$ and $^{16}O$. The $pi^pmSigma^mp / K^-_{stop}$ emission rates are reported as a function of $A$. The
se rates are discussed in comparison with previous findings. The ratio $pi^-Sigma^+/pi^+Sigma^-$ in p-shell nuclei is found to depart largely from that on hydrogen, which provides support for large in-medium effects possibly generated by the sub-threshold $Lambda(1405)$. The continuum momentum spectra of prompt pions and free sigmas are also discussed as well as the $pi^pmSigma^mp$ missing mass behavior and the link with the reaction mechanism. The apparatus used for the investigation is the FINUDA spectrometer operating at the DA$Phi$NE $phi$-factory (LNF-INFN, Italy).
The FINUDA experiment collected data to study the production of hypernuclei on different nuclear targets. The hypernucleus formation occurred through the strangeness-exchange reaction $K^-_{stop} + ; ^AZ rightarrow ; ^A_{Lambda}Z + pi^-$. From the an
alysis of the momentum of the emerging $pi^-$, binding energies and formation probabilities of $^7_{Lambda}$Li, $^9_{Lambda}$Be, $^{13}_{Lambda}$C and $^{16}_{Lambda}$O have been measured and are here presented. The behavior of the formation probability as a function of the atomic mass number A is also discussed.
The Non-Mesonic (NM) decay of $^4_Lambda{mathrm{He}}$ and $^5_Lambda{mathrm{He}}$ in two-body channels has been studied by the FINUDA Collaboration. Two-body NM decays of hypernuclei are rare and the existing observations and theoretical calculations
are scarce. The $^4_Lambda{mathrm{He}}rightarrow d+d,; p+t$ decay channels simultaneously observed by FINUDA on several nuclei are compared: the $pt$ channel is the dominant one. The decay yields for the two decay channels are assessed for the first time: they are $(1.37pm 0.37)times 10^{-5}/K^-_{stop}$ and $(8.3pm 1.0)times 10^{-5}/K^-_{stop}$, respectively. Due to the capability of FINUDA of identifying $^5_Lambda{mathrm{He}}$ hypernuclei, a few $^5_Lambda{mathrm{He}}rightarrow d+t$ decay events have also been observed. The branching ratio for this decay channel has been measured for the first time: $(3.0pm 2.3)times 10^{-3}$.
The FINUDA experiment performed a systematic study of the charged mesonic weak decay channel of $p$-shell $Lambda$-hypernuclei. Negatively charged pion spectra from mesonic decay were measured with magnetic analysis for the first time for ${^{7}_{Lam
bda}Li}$, ${^{9}_{Lambda}Be}$, ${^{11}_{Lambda}B}$ and ${^{15}_{Lambda}N}$. 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 $Gamma_{pi^{-}}/Gamma_{tot}$ were derived from the measured spectra and converted to $pi^{-}$ decay rates $Gamma_{pi^{-}}$ by means of known or extrapolated total decay widths $Gamma_{tot}$ of $p$-shell $Lambda$-hypernuclei. Based on these measurements, the spin-parity assignment $1/2^+$ for ${^{7}_{Lambda}Li}$ and $5/2^+$ for ${^{11}_{Lambda}B}$ ground-state are confirmed and a spin-parity $3/2^+$ for ${^{15}_{Lambda}N}$ ground-state is assigned for the first time.
Novel data from the $K^{-}_{stop}A$ absorption reaction in light nuclei $^{6,7}$Li and $^{9}$Be are presented. The study aimed at finding $Lambda t$ correlations. Regardless of $A$, the $Lambda t$ pairs are preferentially emitted in opposite directio
ns. Reaction modeling predominantly assigns to the $K^-_{stop}AtoLambda t(N)A$ direct reactions the emission of the $Lambda t$ pairs whose yield is found to range from $10^{-3}$ to $10^{-4}$$/K^-_{stop}$. The experiment was performed with the FINUDA spectrometer at DA$Phi$NE (LNF).
The results of a measurement of the proton spectra following the Non--Mesonic Weak Decay of $mathrm{^5_{Lambda}He}$, $mathrm{^7_{Lambda}Li}$ and $mathrm{^{12}_{Lambda}C}$ are presented and discussed. The experiment was performed at the ($e^+$ $e^-$)
collider DA$Phi$NE at Laboratori Nazionale di Frascati of INFN. It is the first measurement for $mathrm{^7_{Lambda}Li}$, and for all the spectra the lower limit on the energy of the protons is 15 MeV, never reached before. All the spectra show a similar shape, namely a peak at around 80 MeV as expected for the free $Lambda p to np$ weak reaction, with a low energy rise that should be due to Final State Interactions and/or two--nucleon induced weak processes. The decay spectrum of $mathrm{^5_{Lambda}He}$ is somehow similar to the ones reported by previous measurements and theoretical calculations, but the same doesnt happen for the $mathrm{^{12}_{Lambda}C}$ one.
Correlated $Lambda d$ pairs emitted after the absorption of negative kaons at rest $K^{-}_{stop}Ato Lambda d A$ in light nuclei $^6Li$ and $^{12}C$ are studied. $Lambda$-hyperons and deuterons are found to be preferentially emitted in opposite direct
ions. The $Lambda d$ invariant mass spectrum of $^6Li$ shows a bump whose mass is 3251$pm$6 MeV/c$^2$. The bump mass (binding energy), width and yield are reported. The appearance of a bump is discussed in the realm of the [$bar{K}3N$] clustering process in nuclei. The experiment was performed with the FINUDA spectrometer at DA$Phi$NE (LNF).
