We have carried out an experiment to search for a neutron-rich hypernucleus, $^6_{Lambda}$H, by the $^6$Li($pi^-,K^+$) reaction at $p_{pi^-}$ =1.2 GeV/$c$. The obtained missing mass spectrum with an estimated energy resolution of 3.2 MeV (FWHM) showe
d no peak structure corresponding to the $^6_{Lambda}$H hypernucleus neither below nor above the $^4_{Lambda}$H$+2n$ particle decay threshold. An upper limit of the production cross section for the bound $^6_{Lambda}$H hypernucleus was estimated to be 1.2 nb/sr at 90% confidence level.
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).
A direct experimental evidence of the occurrence of the weak reaction $Lambda nprightarrow nnp$ in nuclei has been obtained by the FINUDA experiment. Three events have been found that can be attributed to $^{7}_{Lambda}$Li and $^{9}_{Lambda}$Be two n
ucleon-induced non mesonic weak decays. The kinematic analysis of such events is presented here.
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.
