Measurement of the ratio of the B${}_{\mathrm{c}}^{+}$ $\to$ J/$\ddot{I}ˆ$$\ddot{I}{„}^{+}\hat{I}{½}_{\ddot{I}}„$ and B${}_{\mathrm{c}}^{+}$ $\to$ J/$\ddot{I}ˆ$ $\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$ branching fractions using three-prong $\ddot{I}„$ lepton decays

Abstract

The ratio between the B${}_{\mathrm{c}}^{+}$ $\to$ J/$\ddot{I}ˆ$$\ddot{I}{„}^{+}\hat{I}{½}_{\ddot{I}}„$ and B${}_{\mathrm{c}}^{+}$ $\to$ J/$\ddot{I}ˆ$$\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼$ branching fractions is measured using a data sample of proton-proton collisions collected by CMS at a center-of-mass energy of 13 TeV in the years 2016$-$2018 and corresponding to an integrated luminosity of 138 fb${}^{-1}$. The J$/\ddot{I}ˆ$ meson is identified through its J$/\ddot{I}ˆ$ $\to$ $\hat{I}{¼}^{+}\hat{I}{¼}^{-}$ decay and the tau lepton is reconstructed in the hadronic three-prong final state. The measured ratio of branching fractions in this tau decay mode, ${\mathcal{R}}_{\mathrm{J}/\ddot{I}ˆ}^{\text{had}}$ = 1.04 ${}_{-0.44}^{+0.50}$, is combined with the previous analysis based on the $\ddot{I}{„}^{+}$ $\to$ $\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼\bar{\hat{I}}{½}_{\ddot{I}}„$ leptonic decay channel, leading to ${\mathcal{R}}_{\mathrm{J}/\ddot{I}ˆ}$ = 0.49 $\pm$ 0.26. As this result is consistent with the standard model prediction of 0.258 $\pm$ 0.004, no evidence of lepton flavor universality violation is found.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/BPH-23-001 (CMS Public Pages)