The Search for B+→τ+ντ at BaBar

We present a search for the decay B+→τ+ντ using 288 fb−1 of data collected at the ϒ(4S) resonance with the BaBar detector at the SLAC PEP-II B-Factory. A sample of events with one reconstructed semileptonic B decay is selected, and in the recoil a search for B+→τ+ντ signal is performed. The τ is identified in the following channels: , , and . We measure a branching fraction of and extract an upper limit on the branching fraction, at the 90% confidence level, of B(B+→τ+ντ)<1.8×10−4. We calculate the product of the B meson decay constant and |Vub| to be .