Search for the Direct DecayK+→π++γ+γ

Abstract

The measurement of the branching ratio for the direct decay $K^{+}\to {\pi }^{+}+\gamma +\gamma$, where the invariant mass of the two gamma rays is not equal to the ${\pi }^0$ mass, has considerable theoretical importance. We have experimentally established an upper limit of 1.1×${10}^{-4\mathrm{}}$ for this branching ratio. We have used our results to set a limit on the off-the-mass-shell variation of the $K^{+}\to {\pi }^{+}+{\pi }^0$ amplitude.