Measurement of the branching fraction ratios $R(D^{+})$ and $R(D^{\ast +})$ using muonic $\tau$ decays

Abstract

The branching fraction ratios of ${\overline{B}}^0\to D^{+}{\tau }^{-}{\overline{\nu }}_{\tau }$ and ${\overline{B}}^0\to D^{\ast +}{\tau }^{-}{\overline{\nu }}_{\tau }$ decays are measured with respect to their muonic counterparts, using a data sample corresponding to an integrated luminosity of 2.0 fb${}^{-1}$ collected by the LHCb experiment in proton-proton collisions at $\sqrt{s}=13$ TeV. The reconstructed final states are formed by combining $D^{+}$ mesons with ${\tau }^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }{\nu }_{\tau }$ candidates, where the $D^{+}$ is reconstructed via the $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$ decay. The results are \begin{align*} R(D^{+}) &= 0.249 \pm 0.043 \pm 0.047, R(D^{*+}) &= 0.402 \pm 0.081\pm 0.085, \end{align*} where the first uncertainties are statistical and the second systematic. The two measurements have a correlation coefficient of $-0.39$ and are compatible with the Standard Model.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/1792 (LHCb public pages)

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