A search for the decay B+ -> K+ nu nubar

We present a search for the rare flavor-changing neutral-current decay $B^+ \to K^+ \nu \bar{\nu}$ based on data sample of 82 fb$^{-1}$ collected with the 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, a combined limit of ${\mathcal B}(B^+ \to K^+ \nu\bar{\nu})<5.2 \times 10^{-5}$ is obtained at the 90% confidence level. In addition, by modifying the particle identification criteria, a limit of ${\mathcal B} (B^+\to\pi^+\nu\bar{\nu})<1.0 \times 10^{-4}$ is obtained using hadronic $B$ reconstruction. All results are preliminary.