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| Main Author: | |
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| Format: | Preprint |
| Published: |
2024
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2408.00678 |
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Table of Contents:
- A measurement of the ratio of branching fractions $R$(J/$ψ$) = $\mathcal{B}$(B$^+_\text{c}$ $\to$ J/$ψ$$τ^+ν_τ$) / $\mathcal{B}$(B$^+_\text{c}$ $\to$ J/$ψ$$μ^+ν_μ$) in the J/$ψ$ $\to$ $μ^+μ^-$, $τ^+$ $\to$ $μ^+μ_τ\overlineν_τ$ decay channel is presented. This measurement uses a sample of proton-proton collision data collected at a center-of-mass energy of 13 TeV by the CMS experiment in 2018, corresponding to an integrated luminosity of 59.7 fb$^{-1}$. The measured ratio, $R$(J/$ψ$) = 0.17 $^{+ 0.18}_{- 0.17}$ (stat) $^{+ 0.21}_{- 0.22}$ (syst) $^{+ 0.19}_{- 0.18}$ (theo) = 0.17 $\pm$ 0.33, agrees with the value of 0.2582 $\pm$ 0.0038 predicted by the standard model, which assumes lepton flavor universality. By testing lepton flavor universality, this measurement is a probe of new physics using B$^+_\text{c}$ mesons, which are currently only produced at the LHC.