A Search for the Decay B+ to K+ nu nubar

We search for the rare flavor-changing neutral-current decay B+ → K+ ν(bar ν) in a 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 we obtain a combined limit of Β(B+ → K+ ν(bar ν)) < 5.2 x 10-5 at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of Β(B+ → π+ ν(bar ν)) < 1.0 x 10-4 using only the hadronic B reconstruction method