NegativeK-Meson Reactions with Protons: Masses of ChargedΣHyperons and the NegativeKMeson

New measurements of the masses of the charged $\Sigma$ hyperons and the negative $K$ meson are reported. The results obtained are $M_{{\Sigma }^{+}}=1189.3\mathrm{}\pm 0.3$ Mev, $M_{{\Sigma }^{-}}=1195.8\mathrm{}\pm 0.5$ Mev, and $M_{K^{-}}=493.87\mathrm{}\pm 0.46$ Mev. No evidence for more than one $K^{-}$-meson mass was found. The terminal behavior of the ${\Sigma }^{-}$ hyperons was also studied.