A search for the decay $B^{+}\to K^{+}\nu \bar{\nu }$

Abstract

We search for the rare flavor-changing neutral-current decay $B^{+}\to K^{+}\nu \bar{\nu }$ in a data sample of 82 fb${}^{-1}$ collected with the {\sl BABAR} detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of $\mathcal{B}(B^{+}\to K^{+}\nu \bar{\nu })<5.2\times 10^{-5}$ at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of $\mathcal{B}(B^{+}\to {\pi }^{+}\nu \bar{\nu })<1.0\times 10^{-4}$ using only the hadronic B reconstruction method.

7 pages, 8 postscript figures, submitted to Phys. Rev. Lett