Observation and Analysis ofK−Interactions

In nuclear emulsions, 289 $K^{-}$ mesons were observed. The mass and lifetime of $K^{-}$ mesons is the same as that of $K^{+}$ mesons. The $K^{-}$ mean free path in nuclear emulsion is geometric. Charge-exchange scattering and inelastic $K^{-}$-nucleus scattering are rare. Positive hyperons are emitted in 8% of $K^{-}$ capture stars, negative hyperons in about 9%, hyperfragments in 5%. It is estimated that a ${\Lambda }^0$ is trapped without production of a visible hyperfragment in an additional 8%. A $K^{-}$ is captured by one nucleon with formation of a $\Sigma$ hyperon and a pion in about 0.77 of the cases, with creation of a ${\Lambda }^0$ and a pion in approximately 0.18 of the events. Capture by two nucleons occurs in roughly 0.05 of the cases. From a comparison of production and emission frequencies of $\Sigma$ hyperons it is concluded that an attractive nuclear potential for $\Sigma$ hyperons must be less than 20 Mev. Limits for the mean free paths for ordinary scattering, for charge-exchange scattering, and for absorption of $\Sigma$ hyperons in nuclear matter are given. The trapping of ${\Lambda }^0$ hyperons in nuclei is discussed.