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  • Measurement of the ratio of branching fractions $\mathcal{B}(\overline{B}^0 \to D^{+}\tau^{-}\overline{\nu}_{\tau})/\mathcal{B}(\overline{B}^0 \to D^{+}\mu^{-}\overline{\nu}_{\mu})
    Andreotti, M; Baldini, W; Barlow, R. J; Barsuk, S; Batozskaya, V; Beddow, J; Bedeschi, F; Bellee, V; Ben-Haim, E; Bencivenni, G; Bernet, R; Bonivento, W; Bowcock, T. J. V; Braun, S; Britton, T; Carniti, P; Akiba, K. Carvalho; Cheung, S. -F; Clemencic, M; Coombes, M; Couturier, B; Dalseno, J; Derkach, D; Di Ruscio, F; Falabella, A; Fay, R; Galli, D; Gallorini, S; Gambetta, S; Gandini, P; Gao, Y; Tico, J. Garra; Gianelle, A; Göbel, C; Gándara, M. Grabalosa; Grecu, A; Griffith, P; Grillo, L; Gui, B; Haines, S. C; Harnew, S. T; Harrison, J; Heijne, V; Henry, L; Idzik, M; Jans, E; John, M; Karacson, M; Karodia, S; Klaver, S; Klimaszewski, K; Kochebina, O; Kozeiha, M; Krokovny, P; Lai, A; Latham, T; Lesiak, T; Liu, B; Longstaff, I; Machefert, F; Marks, J; Martinelli, M; Matev, R; Mazurov, A; Meissner, M; Mitzel, D. S; Mountain, R; Müller, V; Mussini, M; Neuner, M; Nguyen, T. D; O'Hanlon, D. P; Oblakowska-Mucha, A; Panman, J; Parkes, C; Passaleva, G; Patel, G. D; Pilař, T; Polci, F; Prisciandaro, J; Redi, F; Mayordomo, C. Sanchez; Santovetti, E; Savrina, D; Schopper, A; Sciascia, B; Sestini, L; Smith, E; Souza, D; De Paula, B. Souza; Tellarini, G; Thomas, C; Tobin, M; Vallier, A; Vieira, D; Weiden, A; Whitehead, M; Williams, M. P; Wyllie, K; Zhokhov, A

    06/2015
    Journal Article

    Phys. Rev. Lett. 115, 111803 (2015) The branching fraction ratio $\mathcal{R}(D^{*}) \equiv \mathcal{B}(\overline{B}^0 \to D^{*+}\tau^{-}\overline{\nu}_{\tau})/\mathcal{B}(\overline{B}^0 \to D^{*+}\mu^{-}\overline{\nu}_{\mu})$ is measured using a sample of proton-proton collision data corresponding to 3.0\invfb of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $\tau^{-} \to \mu^{-}\overline{\nu}_{\mu}\nu_{\tau}$. The semitauonic decay is sensitive to contributions from non-Standard-Model particles that preferentially couple to the third generation of fermions, in particular Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate $\overline{B}^0$ decays gives $\mathcal{R}(D^{*}) = 0.336 \pm 0.027(stat) \pm 0.030 (syst)$. This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the Standard Model.

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