We present the results of a measurement of the $\frac{{K_{\mu 3}}^0}{{K_{e3\mathrm{}}}^0}$ branching ratio, obtained from a study of ${K_L}^0$ decays using a multiwire-proportional-chamber spectrometer. The ${K_{\mu 3}}^0$ and ${K_{e3\mathrm{}}}^0$ events were separated by muon range counters, and ${K_{\pi 3}}^0$ events were separated from the ${K_{e3\mathrm{}}}^0$ sample kinematically. From a sample of approximately 10000 ${K_{\mu 3}}^0$ and ${K_{e3\mathrm{}}}^0$ events, we obtain a value of the branching ratio $\frac{\Gamma \left({K_{\mu 3}}^0\right)}{\Gamma \left({K_{e3\mathrm{}}}^0\right)}=0.662\mathrm{}\pm 0.037$.

• Received 28 March 1974

DOI:https://doi.org/10.1103/PhysRevLett.33.240