Measurement of the Lifetime of the Short-Lived NeutralKMeson

A measurement of the lifetime of the short-lived neutral $K$ meson ($K_S$) was made based on the analysis of about 20 000 $K_S\to {\pi }^{+}+{\pi }^{-}$ decays observed in the BNL 30-in. bubble chamber filled with deuterium. An extensive study has been made of possible systematic errors. We obtain as our best estimate of the $K_S$ mean lifetime ${\tau }_S=(0.865\mathrm{}\pm 0.009)\times {10}^{-10\mathrm{}}$ sec.