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arXiv · 1712.04123

Search for $B^{-}\to\mu^{-}\bar\nu_\mu$ Decays at the Belle Experiment

Belle Collaboration·A. Sibidanov·K. E. Varvell·I. Adachi·H. Aihara·S. Al Said·D. M. Asner·T. Aushev·R. Ayad·V. Babu·I. Badhrees·S. Bahinipati·A. M. Bakich·V. Bansal·E. Barberio·P. Behera·B. Bhuyan·J. Biswal·A. Bozek·M. Bračko·T. E. Browder·D. Červenkov·P. Chang·V. Chekelian·A. Chen·B. G. Cheon·K. Chilikin·K. Cho·S. -K. Choi·Y. Choi·D. Cinabro·T. Czank·N. Dash·S. Di Carlo·Z. Doležal·Z. Drásal·D. Dutta·S. Eidelman·D. Epifanov·J. E. Fast·T. Ferber·B. G. Fulsom·V. Gaur·N. Gabyshev·A. Garmash·P. Goldenzweig·D. Greenwald·Y. Guan·E. Guido·J. Haba·K. Hayasaka·H. Hayashii·M. T. Hedges·S. Hirose·W. -S. Hou·C. -L. Hsu·T. Iijima·K. Inami·G. Inguglia·A. Ishikawa·R. Itoh·M. Iwasaki·Y. Iwasaki·W. W. Jacobs·I. Jaegle·H. B. Jeon·Y. Jin·K. K. Joo·T. Julius·J. Kahn·A. B. Kaliyar·K. H. Kang·G. Karyan·T. Kawasaki·C. Kiesling·D. Y. Kim·J. B. Kim·S. H. Kim·Y. J. Kim·K. Kinoshita·P. Kodyš·S. Korpar·D. Kotchetkov·P. Križan·P. Krokovny·T. Kuhr·R. Kulasiri·R. Kumar·A. Kuzmin·Y. -J. Kwon·J. S. Lange·I. S. Lee·C. H. Li·L. Li·L. Li Gioi·J. Libby·D. Liventsev·M. Lubej·T. Luo·M. Masuda
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Abstract

We report the result of a search for the decay $B^{-}\to\mu^{-}\bar\nu_\mu$. The signal events are selected based on the presence of a high momentum muon and the topology of the rest of the event showing properties of a generic $B$-meson decay, as well as the missing energy and momentum being consistent with the hypothesis of a neutrino from the signal decay. We find a 2.4 standard deviation excess above background including systematic uncertainties, which corresponds to a branching fraction of ${\cal B}(B^{-}\to\mu^{-}\bar\nu_\mu) =(6.46 \pm 2.22 \pm 1.60 )\times10^{-7}$ or a frequentist 90% confidence level interval on the $B^{-}\to\mu^{-}\bar\nu_\mu$ branching fraction of $[2.9, 10.7]\times 10^{-7}$. This result is obtained from a $711\ \text{fb}^{-1}$ data sample that contains $772 \times 10^6$ $B\bar{B}$ pairs, collected near the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider.

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Belle Collaboration, A. Sibidanov, K. E. Varvell, I. Adachi, H. Aihara, S. Al Said, D. M. Asner, T. Aushev, R. Ayad, V. Babu, I. Badhrees, S. Bahinipati, A. M. Bakich, V. Bansal, E. Barberio, P. Behera, B. Bhuyan, J. Biswal, A. Bozek, M. Bračko, T. E. Browder, D. Červenkov, P. Chang, V. Chekelian, A. Chen, B. G. Cheon, K. Chilikin, K. Cho, S. -K. Choi, Y. Choi, D. Cinabro, T. Czank, N. Dash, S. Di Carlo, Z. Doležal, Z. Drásal, D. Dutta, S. Eidelman, D. Epifanov, J. E. Fast, T. Ferber, B. G. Fulsom, V. Gaur, N. Gabyshev, A. Garmash, P. Goldenzweig, D. Greenwald, Y. Guan, E. Guido, J. Haba, K. Hayasaka, H. Hayashii, M. T. Hedges, S. Hirose, W. -S. Hou, C. -L. Hsu, T. Iijima, K. Inami, G. Inguglia, A. Ishikawa, R. Itoh, M. Iwasaki, Y. Iwasaki, W. W. Jacobs, I. Jaegle, H. B. Jeon, Y. Jin, K. K. Joo, T. Julius, J. Kahn, A. B. Kaliyar, K. H. Kang, G. Karyan, T. Kawasaki, C. Kiesling, D. Y. Kim, J. B. Kim, S. H. Kim, Y. J. Kim, K. Kinoshita, P. Kodyš, S. Korpar, D. Kotchetkov, P. Križan, P. Krokovny, T. Kuhr, R. Kulasiri, R. Kumar, A. Kuzmin, Y. -J. Kwon, J. S. Lange, I. S. Lee, C. H. Li, L. Li, L. Li Gioi, J. Libby, D. Liventsev, M. Lubej, T. Luo, M. Masuda. 2017-12-12. Search for $B^{-}\to\mu^{-}\bar\nu_\mu$ Decays at the Belle Experiment. https://doi.org/10.1103/physrevlett.121.031801

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