Limits on theK+→π++ν+ν¯andK+→π++nγDecay Rates

The branching ratio for the process $K^{+}\to {\pi }^{+}+\nu +\overline{\nu }$ is shown by a counter—spark-chamber experiment to be less than 1.4×${10}^{-6\mathrm{}}$ of all decay modes, assuming a pion energy spectrum like that of $K^{+}\to {\pi }^0+e^{+}+\nu$. The apparatus was sensitive to pions in the kinetic-energy range 117-127 MeV. For the same energy interval a limit of 5×${10}^{-5\mathrm{}}$ is established for the process $K^{+}\to {\pi }^{+}+\gamma +\gamma$, assuming a phase-space model for the decay. A limit of 4×${10}^{-6\mathrm{}}$ is established for the process $K^{+}\to {\pi }^{+}+\gamma$.