CMS-PAS-BPH-23-001

CMS-PAS-BPH-23-001
Measurement of the ratio of the $ \text{B}_\text{c}^{+}\to\text{J}/\psi\tau^{+}\nu_\tau $ and $ \text{B}_\text{c}^{+}\to\text{J}/\psi\mu^{+}\nu_\mu $ branching fractions using three-prong $ \tau $ lepton decays in proton-proton collisions at $ \sqrt{s}= $ 13 TeV
CMS Collaboration
29 August 2024

Abstract: A measurement of the ratio of branching fractions $ \mathcal{R}_{\text{J}/\psi} = \mathcal{B}(\text{B}_\text{c}^{+}\to\text{J}/\psi\tau^{+}\nu_\tau) / \mathcal{B}(\text{B}_\text{c}^{+}\to\text{J}/\psi\mu^{+}\nu_\mu) $ in the decay channel with $ \text{J}/\psi(\rightarrow\mu^{+}\mu^{-}) $ and $ \tau^{+}\rightarrow\pi^{+}\pi^{-}\pi^{+}(+\pi^{0})\bar{\nu}_{\tau} $ (and charge-conjugated processes) is presented. This measurement uses a sample of proton-proton collision data, corresponding to an integrated luminosity of 138 fb$ ^{-1} $, collected at a center-of-mass energy of 13 TeV by the CMS experiment in the LHC Run 2. The ratio is measured to be $ \mathcal{R}_{\text{J}/\psi}= 1.04 _{-0.44}^{+0.50} $, which in combination with the measurement of $ \mathcal{R}_{\text{J}/\psi} $ in the decay channel with $ \text{J}/\psi\rightarrow\mu^{+}\mu^{-} $ and $ \tau^{+}\rightarrow\mu^{+}\nu_{\mu}\bar{\nu}_{\tau} $, yields $ \mathcal{R}_{\text{J}/\psi}= $ 0.49 $ \pm $ 0.25 $ \,\mathrm{(stat)} \pm 0.09\,\mathrm{(syst)} $ in agreement with the value predicted by the standard model of particle physics, 0.258 $ \pm $ 0.004.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here.

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