Measurement of the ratio of branching fractions $\mathcal{B}(B_c^+\,\to\,J/\psi\tau^+\nu_\tau)$/$\mathcal{B}(B_c^+\,\to\,J/\psi\mu^+\nu_\mu)$

Abstract : 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+νμν¯τ. 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.
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Journal articles

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Submitted on : Wednesday, April 4, 2018 - 3:02:17 PM
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Citation

R. Aaij, Bernardo Adeva, Marco Adinolfi, Ziad Ajaltouni, Simon Akar, et al.. Measurement of the ratio of branching fractions $\mathcal{B}(B_c^+\,\to\,J/\psi\tau^+\nu_\tau)$/$\mathcal{B}(B_c^+\,\to\,J/\psi\mu^+\nu_\mu)$. Phys.Rev.Lett., 2018, 120 (12), pp.121801. ⟨10.1103/PhysRevLett.120.121801⟩. ⟨hal-01758475⟩

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