Optical Model for Production ofΣParticles in Nuclei by NegativeKMesons

The experimental data of Gilbert, Violet, and White, concerning the charged $\Sigma$ particles emitted when negative $K$ particles are stopped in photographic emulsions, are interpreted by means of an optical model. It is assumed that the primary absorption interaction involves directly only a single nucleon, and that the impulse approximation is valid in this interaction. The observed spectra of ${\Sigma }^{+}$ and ${\Sigma }^{-}$ particles emitted in two-prong stars indicate that the charge-independent part of the $\Sigma$-particle nuclear potential in the model must be attractive. From a comparison of the emulsion data with the results of stopping $K^{-}$ particles in a hydrogen bubble chamber, limits are placed on the possible size of the cross section in nuclei for the absorption of charged $\Sigma$ particles by means of conversion to neutral $\Sigma$ or $\Lambda$ particles.