Search for the rare decayK+→π+e+e−

A search for the rare decay $K^{+}\to {\pi }^{+}{e}^{+}{e}^{-}$ has been carried out at the Lawrence Berkeley Laboratory using a sparkostrictive wire-chamber spectrometer. Analysis programs identified events with three tracks or with two tracks of which one was an electron and the other a positron. Analysis of the three-track events yields a branching ratio $\frac{\Gamma (K^{+}\to {\pi }^{+}{e}^{+}{e}^{-})}{\Gamma (K^{+}\to \mathrm{all})}<1.7\mathrm{}\times {10}^{-6\mathrm{}}$ (90% confidence). The two-track events, analyzed by searching for sparks on a possible pion track, yield a limit of $\frac{\Gamma (K^{+}\to {\pi }^{+}{e}^{+}{e}^{-})}{\Gamma (K^{+}\to \mathrm{all})}<2.7\mathrm{}\times {10}^{-7\mathrm{}}$ (90% confidence). The latter value implies that the coupling constant for a vector neutral current must be about three orders of magnitude smaller than the coupling constant for the charged vector current.