K20Decay

Abstract

A sample of $479 {K_2}^0$ decays in the BNL 20-in. hydrogen bubble chamber was obtained. Of these, 153 are identified as ${K_2}^0\to \left({\pi }^{\pm }{e}^{\mp }\nu \right)$ decay. The validity of $\mathrm{CP}$ invariance is suggested by the upper limit of 1.5% we are able to place on the fraction of all ${K_2}^0$ decays which result in two charged pions; and by the ratio $\frac{\left({\pi }^{+}{e}^{-}\nu \right)}{\left({\pi }^{-}{e}^{+}\nu \right)}=0.99\mathrm{}\pm 0.16$. The (${\pi }^{\pm }{e}^{\mp }\nu$) decay is found to proceed by the vector interaction, with an approximately constant form factor. The ratio $\frac{{K_{\mu 3}}^0}{{K_{e3\mathrm{}}}^0}=0.73\mathrm{}\pm 0.15$ implies that the ratio of the two form factors appearing in $K_{\mu 3}$ decay $\frac{f_{-}}{f_{+}}$ is consistent with zero. The fraction of visible ${K_2}^0$ decays which result in (${\pi }^{+}{\pi }^{-}{\pi }^0$) is 0.157±0.03. The prediction obtained by using the $\Delta I=\frac{1}{2}$ currents is 0.152±0.017. Our data may be combined with other experiments to provide additional tests of the $\Delta I=\frac{1}{2}$ rule.