π+-Mesonic Decay of a Hyperfragment

The ${\pi }^{+}$-mesonic decay of a hyperfragment has been observed. The hyperfragment was produced in a negative $K$-meson star in emulsion, and it decayed into two visible particles, a ${\pi }^{+}$-meson and a recoil. It can be interpreted as ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{Li}_{}^7{}_{}{}^{}\to n+\pi +{\mathrm{He}}^6$, or ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{Be}_{}^7{}_{}{}^{}\to n+{\pi }^{+}+{\mathrm{Li}}^6$. Since the $\Lambda$ particle decays only into $p+{\pi }^{-}$ and $n+{\pi }^0$, the appearance of a ${\pi }^{+}$-meson from this hyperfragment is explained as due to the charge exchange of a ${\pi }^0$-meson from the $\Lambda$ decay with the residual nucleus of the hyperfragment.