Evidence of B+->tau nu decays with hadronic B tags

J.P. Lees (1) , V. Poireau (1) , V. Tisserand (1) , N. Arnaud (2) , M. Davier (2) , D. Derkach (2) , G. Grosdidier (2) , F. Le Diberder (2) , A.M. Lutz (2) , B. Malaescu (3) , P. Roudeau (2) , M.H. Schune (2) , A. Stocchi (2) , G. Wormser (2) , D. Bernard (4) , M. Verderi (4) , S. Emery (5) , G. Hamel de Monchenault (5) , G. Vasseur (5) , Ch. Yèche (5) , S. Akar (3) , E. Ben-Haim (3) , M. Bomben (3) , G.R. Bonneaud (3) , H. Briand (3) , G. Calderini (3) , J. Chauvau (3) , O. Hamon (3) , Ph. Leruste (3) , G. Marchiori (3) , J. Ocariz (3) , S. Sitt (3)

1 LAPP - Laboratoire d'Annecy de Physique des Particules
2 LAL - Laboratoire de l'Accélérateur Linéaire
3 LPNHE - Laboratoire de Physique Nucléaire et de Hautes Énergies
4 LLR - Laboratoire Leprince-Ringuet
5 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers

We present a search for the decay B+ -->tau+ nu using 467.8 x 10^6 B B pairs collected at the Y(4S) resonance with the BaBar detector at the SLAC PEP-II B-Factory. We select a sample of events with one completely reconstructed B- in the hadronic decay modes (B- --> D(*)0 X- and B- --> J/\psi X-). We 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+ --> rho+ nu. We find an excess of events with respect to the expected background, which excludes the null signal hypothesis at the level of 3.8 sigma (including systematic uncertainties) and corresponds to a branching fraction central value of B(B+ --> tau+ nu)=(1.83^{+0.53}_{-0.49}(stat.) +/- 0.24 (syst.)) x 10^-4.

Domaines: Physique des Hautes Energies - Expérience [hep-ex]

J.P. Lees, V. Poireau, V. Tisserand, N. Arnaud, M. Davier, et al.. Evidence of B+->tau nu decays with hadronic B tags. Physical Review D, 2013, 88, pp.031102. ⟨10.1103/PhysRevD.88.031102⟩. ⟨in2p3-00861265⟩