The decay $K_L^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ has been studied in an experiment using the Argonne 12-ft hydrogen bubble chamber exposed to a $K_L^0$ beam of momentum 550 ± 35 MeV/c. After radiative corrections to the data, a fit using a matrix element of the form ${\mathrm{}\left|M\right|\mathrm{}}^2\propto 1+\frac{g(s_3-s_0)}{{m_{{\pi }^{+}}}^2}+h{\left[\frac{(s_3 - s_0)}{{m_{{\pi }^{+}}}^2}\right]}^2 + k{\left[\frac{(s_1 - s_2)}{{m_{{\pi }^{+}}}^2}\right]}^2$ gives $g = 0.681\pm 0.24$, $h = 0.095\pm 0.032$, and $k = 0.024\pm 0.010$. The branching ratio $\frac{\Gamma (K_L^0\to {\pi }^{+}{\pi }^{-}{\pi }^0)}{\Gamma (K_L^0\to \mathrm{charged})}$ was measured to be 0.163 ± 0.003. These results, when compared to those obtained in other $K_L^0$ and $K^{\pm }$ decay experiments, indicate a substantial $\Delta >\frac{1}{2}$ contribution to the $K_L^0$ decay amplitude.

• Received 15 September 1976

DOI:https://doi.org/10.1103/PhysRevD.15.587