Measurement of the Ratio of Branching Fractions ℬ(Bc+→j/ψτ+ντ)/ℬ(Bc+→j/ψμ+νμ)

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  • R. Aaij
  • B. Adeva
  • M. Adinolfi
  • Z. Ajaltouni
  • S. Akar
  • J. Albrecht
  • F. Alessio
  • M. Alexander
  • A. Alfonso Albero
  • S. Ali
  • G. Alkhazov
  • P. Alvarez Cartelle
  • A. A. Alves
  • S. Amato
  • S. Amerio
  • Y. Amhis
  • L. An
  • L. Anderlini
  • G. Andreassi
  • M. Andreotti
  • J. E. Andrews
  • R. B. Appleby
  • F. Archilli
  • P. D'Argent
  • J. Arnau Romeu
  • A. Artamonov
  • M. Artuso
  • E. Aslanides
  • M. Atzeni
  • G. Auriemma
  • M. Baalouch
  • I. Babuschkin
  • S. Bachmann
  • J. J. Back
  • A. Badalov
  • C. Baesso
  • S. Baker
  • V. Balagura
  • W. Baldini
  • Simone Bifani
  • R. Calladine
  • G. Chatzikonstantinidis
  • N. Farley
  • Cristina Lazzeroni
  • A. Mazurov
  • Antonino Sergi
  • Nigel Watson
  • Matt Williams
  • K. A. Zarebski
  • LHCb Collaboration
  • Timothy Williams

Colleges, School and Institutes

External organisations

  • Laboratory of Photonics and Interfaces, Department de Chimie, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland.
  • European Organization for Nuclear Research (CERN)
  • Universidad de Santiago de Compostela
  • LPC
  • University of Cincinnati
  • Technische Universität Dortmund
  • University of Glasgow
  • Universitat Autònoma de Barcelona
  • Nikhef National Institute for Subatomic Physics
  • Petersburg Nuclear Physics Institute (PNPI)
  • Imperial College London
  • Universidade Federal Do Rio de Janeiro (UFRJ)
  • Department of Physics and Astronomy and INFN
  • IN2P3
  • Tsinghua University
  • Department of Biology and Evolution; University of Ferrara; Ferrara; Italy
  • University of Maryland, College Park, Maryland 20742 USA
  • University of Manchester
  • Ruprecht-Karls-Universität Heidelberg
  • CNRS/IN2P3
  • Institute for High Energy Physics (IHEP)
  • Syracuse University, Syracuse, New York 13244, USA
  • Universität Zürich
  • Universitat Ramon Llull
  • Pontifícia Universidade Católica Do Rio de Janeiro (PUC-Rio)
  • Laboratoire Leprince-Ringuet


A measurement is reported of the ratio of branching fractions ℛ(J/ψ)=ℬ(Bc+→J/ψτ+ντ)/ℬ(Bc+→J/ψμ+νμ), where the τ+ lepton is identified in the decay mode τ+→μ+νμτ. This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb-1 of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay Bc+→J/ψτ+ντ at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be ℛ(J/ψ)=0.71±0.17(stat)±0.18(syst). This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.


Original languageEnglish
Article number121801
Number of pages10
JournalPhysical Review Letters
Issue number12
Publication statusPublished - 23 Mar 2018

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