A Search for B+ --> tau+ nu Recoiling Against B- --> D0 l- nubar X

الأصل · EN

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: τ+ → e+ νₑ, τ+ → μ+ νμ, τ+ → π+ and τ+ → π+ π⁰. We measure a branching fraction of B(B⁺ → τ⁺ ντ)=(0.88⁺⁰.⁶⁸₋₀.₆₇(stat.) ± 0.11 (syst.)) × 10⁻⁴ 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 || to be fB·|| = (7.0⁺².³₋₃.₆(stat.)⁺⁰.⁴₋₀.₅(syst.))×10⁻⁴ GeV