Evidence for Violation of theΔI=12Rule inK+→3πDecay

Abstract

A significant violation of the $\Delta I=\frac{1}{2}$ rule has been detected in $K^{+}\to 3\pi$ decay. The ratio of the coefficients of the linear terms in the squared matrix elements of ${\tau }^{\prime +} (K^{+}\to {\pi }^{+}+2\mathrm{}{\pi }^0)$ and ${\tau }^{+} (K^{+}\to 2{\pi }^{+}+{\pi }^{-})$ is found to be -2.63 ± 0.18 (as compared with the $\Delta I=\frac{1}{2}$ rule prediction of -2), when the results of the Riverside ${\tau }^{\prime +}$ experiment are used together with the results of the present ${\tau }^{+}$ experiment.