New experimental upper limit for the decayK±→γγ

We have searched for the rare decay mode $K^{\pm }{\pi }^{\pm }\gamma \gamma$ using scintillation counters, optical spark chambers, and a wire-spark-chamber spectrometer. After background subtraction we obtain a branching ratio of (-4.2 ± 5.2) × ${10}^{-5\mathrm{}}$. The result is somewhat model-dependent. The quoted branching ratio, which comes from a fit to the phase-space model, is the highest value obtained from the various models considered.