Garra Ticó, JordiGraugés Pous, EugeniBABAR Collaboration2019-04-042019-04-042007-09-181550-7998https://hdl.handle.net/2445/131444We present a search for the decay B + → τ + ν using 383 × 10 6 B ¯¯¯ B pairs collected at the Υ ( 4 S ) resonance with the BABAR detector at the SLAC PEP-II B -Factory. A sample of events with one reconstructed semileptonic B decay ( B − → D 0 ℓ − ¯ ν ℓ X ) is selected, and in the recoil a search for B + → τ + ν is performed. The τ is identified in the following channels: τ + → e + ν ¯ ν , τ + → μ + ν ¯ ν , τ + → π + ¯ ν , and τ + → π + π 0 ¯ ν . We measure a branching fraction of B ( B + → τ + ν ) = ( 0.9 ± 0.6 ( stat . ) ± 0.1 ( syst . ) ) × 10 − 4 . In the absence of a significant signal, we calculate an upper limit at the 90% confidence level of B ( B + → τ + ν ) < 1.7 × 10 − 4 . We calculate the product of the B meson decay constant f B and | V ub | to be f B ⋅ | V ub | = ( 7.2 + 2.0 − 2.8 ( stat . ) ± 0.2 ( syst . ) ) × 10 − 4     GeV .12 p.application/pdfeng(c) American Physical Society, 2007Física de partículesExperimentsParticle physicsExperimentsinfo:eu-repo/semantics/article5581912019-04-04info:eu-repo/semantics/openAccess