A Search for $B\to \tau \nu$

Abstract

We report results of a search for $B\to \tau \nu$ in a sample of 9.7 million charged $B$ meson decays. The search uses both $\pi \nu$ and $\ell \nu \bar{\nu }$ decay modes of the $\tau$, and demands exclusive reconstruction of the companion $\bar{B}$ decay to suppress background. We set an upper limit on the branching fraction $\mathcal{B}(B\to \tau \nu )<8.4\times 10^{-4}$ at 90% confidence level. With slight modification to the analysis we also establish $\mathcal{B}(B^{\pm }\to K^{\pm }\nu \bar{\nu })<2.4\times 10^{-4}$ at 90% confidence level.

10 ages postscript, also available through http://w4.lns.cornell.edu/public/CLNS