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arXiv · 1607.07923

Measurement of the branching ratio of $\bar{B}^0 \rightarrow D^{*+} \tau^- \bar{\nu}_{\tau}$ relative to $\bar{B}^0 \rightarrow D^{*+} \ell^- \bar{\nu}_{\ell}$ decays with a semileptonic tagging method

Y. Sato·T. Iijima·K. Adamczyk·H. Aihara·D. M. Asner·H. Atmacan·T. Aushev·R. Ayad·T. Aziz·V. Babu·I. Badhrees·A. M. Bakich·V. Bansal·P. Behera·V. Bhardwaj·B. Bhuyan·J. Biswal·G. Bonvicini·A. Bozek·M. BraD. P. Chang·V. Chekelian·A. Chen·B. G. Cheon·K. Chilikin·R. Chistov·K. Cho·V. Chobanova·Y. Choi·D. Cinabro·M. Danilov·N. Dash·S. Di Carlo·Z. DoleD. Dutta·S. Eidelman·D. Epifanov·H. Farhat·J. E. Fast·T. Ferber·B. G. Fulsom·V. Gaur·N. Gabyshev·A. Garmash·P. Goldenzweig·B. Golob·D. Greenwald·K. Hara·T. Hara·J. Hasenbusch·K. Hayasaka·H. Hayashii·S. Hirose·T. Horiguchi·W. -S. Hou·K. Inami·A. Ishikawa·R. Itoh·Y. Iwasaki·I. Jaegle·H. B. Jeon·D. Joffe·T. Julius·K. H. Kang·Y. Kato·P. Katrenko·T. Kawasaki·D. Y. Kim·J. B. Kim·K. T. Kim·M. J. Kim·S. H. Kim·Y. J. Kim·K. Kinoshita·P. KodyS. Korpar·D. Kotchetkov·P. Krokovny·T. Kuhr·R. Kumar·Y. -J. Kwon·J. S. Lange·C. H. Li·L. Li·Y. Li·L. Li Gioi·J. Libby·D. Liventsev·T. Luo·M. Masuda·T. Matsuda·D. Matvienko·K. Miyabayashi·H. Miyata·R. Mizuk·G. B. Mohanty·A. Moll·H. K. Moon·K. R. Nakamura·E. Nakano·M. Nakao·T. Nanut·K. J. Nath
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Abstract

We report a measurement of the ratio ${\cal R}(D^*) = {\cal B}(\bar{B}^0 \rightarrow D^{*+} \tau^- \bar{\nu}_{\tau})/{\cal B}(\bar{B}^0 \rightarrow D^{*+} \ell^- \bar{\nu}_{\ell})$, where $\ell$ denotes an electron or a muon. The results are based on a data sample containing $772\times10^6$ $B\bar{B}$ pairs recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. We select a sample of $B^0 \bar{B}^0$ pairs by reconstructing both $B$ mesons in semileptonic decays to $D^{*\mp} \ell^{\pm}$. We measure ${\cal R}(D^*)= 0.302 \pm 0.030({\rm stat)} \pm 0.011({\rm syst)}$, which is within $1.6 \sigma$ of the Standard Model theoretical expectation, where the standard deviation $\sigma$ includes systematic uncertainties. We use this measurement to constrain several scenarios of new physics in a model-independent approach.

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Y. Sato, T. Iijima, K. Adamczyk, H. Aihara, D. M. Asner, H. Atmacan, T. Aushev, R. Ayad, T. Aziz, V. Babu, I. Badhrees, A. M. Bakich, V. Bansal, P. Behera, V. Bhardwaj, B. Bhuyan, J. Biswal, G. Bonvicini, A. Bozek, M. BraD. P. Chang, V. Chekelian, A. Chen, B. G. Cheon, K. Chilikin, R. Chistov, K. Cho, V. Chobanova, Y. Choi, D. Cinabro, M. Danilov, N. Dash, S. Di Carlo, Z. DoleD. Dutta, S. Eidelman, D. Epifanov, H. Farhat, J. E. Fast, T. Ferber, B. G. Fulsom, V. Gaur, N. Gabyshev, A. Garmash, P. Goldenzweig, B. Golob, D. Greenwald, K. Hara, T. Hara, J. Hasenbusch, K. Hayasaka, H. Hayashii, S. Hirose, T. Horiguchi, W. -S. Hou, K. Inami, A. Ishikawa, R. Itoh, Y. Iwasaki, I. Jaegle, H. B. Jeon, D. Joffe, T. Julius, K. H. Kang, Y. Kato, P. Katrenko, T. Kawasaki, D. Y. Kim, J. B. Kim, K. T. Kim, M. J. Kim, S. H. Kim, Y. J. Kim, K. Kinoshita, P. KodyS. Korpar, D. Kotchetkov, P. Krokovny, T. Kuhr, R. Kumar, Y. -J. Kwon, J. S. Lange, C. H. Li, L. Li, Y. Li, L. Li Gioi, J. Libby, D. Liventsev, T. Luo, M. Masuda, T. Matsuda, D. Matvienko, K. Miyabayashi, H. Miyata, R. Mizuk, G. B. Mohanty, A. Moll, H. K. Moon, K. R. Nakamura, E. Nakano, M. Nakao, T. Nanut, K. J. Nath. 2016-07-27. Measurement of the branching ratio of $\bar{B}^0 \rightarrow D^{*+} \tau^- \bar{\nu}_{\tau}$ relative to $\bar{B}^0 \rightarrow D^{*+} \ell^- \bar{\nu}_{\ell}$ decays with a semileptonic tagging method. https://doi.org/10.1103/physrevd.94.072007

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