Search for the Rare Leptonic Decay B-→τ-ν¯τ

We present a search for the decay B-→τ-ντ̅ in a sample of 88.9×106 BB̅ pairs recorded with the BABAR detector at the Stanford Linear Accelerator Center B factory. One of the two B mesons from the Υ(4S) is reconstructed in a hadronic or a semileptonic final state, and the decay products of the other B in the event are analyzed for consistency with a B-→τ-ν̅ τ decay. We find no evidence of a signal and set an upper limit on the branching fraction of B(B-→τ-ν̅ τ)<4.2×10-4 at the 90% confidence level.