Search forB+→τ+νdecays with hadronicBtags

B. Aubert, M. Bona, D. Boutigny, Y. Karyotakis, J. P. Lees, V. Poireau, X. Prudent, V. Tisserand, A. Zghiche, J. Garra Tico, E. Grauges, L. Lopez (+556 others)
2008 Physical Review D  
We present a search for the decay B^+ --> tau^+ nu using 383 × 10^6 BBbar pairs collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II B Factory. We select a sample of events with one completely reconstructed tag B in a hadronic decay mode (B^- → D^(*)0 X^-), and examine the rest of the event to search for a B^+ --> tau^+ nu decay. We identify the tau lepton in the following modes: tau^+ --> e^+ nu nu,tau^+ --> mu^+ nu nu, tau^+ --> pi^+ nu and tau^+ --> pi^+ pi^0 nu.
more » ... We find a 2.2 sigma excess in data and measure a branching fraction of B(B+ --> tau^+ nu) = (1.8^+0.9_-0.8(stat.) ± 0.4(bkg. syst.) ± 0.2 (other syst.)) × 10^4. We calculate the product of the B meson decay constant f_B and |V_ub| to be f_B |V_ub| = (10.1^+2.3_-2.5(stat.)^+1.2_-1.5(syst.))×10^-4 GeV
doi:10.1103/physrevd.77.011107 fatcat:vl3itt32vfelxfrkgjm7kik5iq