Binding Energies and Lifetimes of Lighter Hyperfragments

In an emulsion stack exposed to a stopping $K^{-}$ beam at the Bevatron, we have observed hyperfragments in order to make lifetime and binding-energy measurements on the lighter hyperfragments formed. We have measured the binding energies of 28 hyperfragments with mass number $7\le A\le 13$. Restricting ourselves to lifetime measurements using the ${\pi }^{-}\mathrm{pr}$ decay modes, we observed three decays in flight, one each of ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{H}_{}^3{}_{}{}^{}$, ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{He}_{}^4{}_{}{}^{}$, and ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{Li}_{}^7{}_{}{}^{}$. Combining our ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{He}$ data with previous measurements, we obtained the lifetime $\left({}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{He}\right)=\left({{1.9}_{-0.4\mathrm{}}}^{+0.6\mathrm{}}\right)\times {10}^{-10\mathrm{}}$ sec for the ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{He}$ group. This value is slightly more than one standard deviation less than the predicted values for ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{He}_{}^4{}_{}{}^{}$ and ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{He}_{}^5{}_{}{}^{}$.