Measurement of the ratio of branching fractions $\mathcal{B}(B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{„}^{+}\hat{I}{½}_{\ddot{I}}„)/\mathcal{B}(B_c^{+}\to J/\ddot{I}ˆ\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)$

Abstract

A measurement of the ratio of semileptonic branching fractions $\mathcal{R}(J\ddot{I}ˆ)$, defined as $\mathcal{R}(J/\ddot{I}ˆ)\equiv \mathcal{B}(B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{„}^{+}\hat{I}{½}_{\ddot{I}}„)/\mathcal{B}(B_c^{+}\to J/\ddot{I}ˆ\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)$, is reported using a sample of proton-proton collision data corresponding to an integrated luminosity of 5.4 fb${}^{-1}$ recorded by the LHCb experiment in 2016--2018 at a center-of-mass energy of 13 TeV. The measured value is found to be $\mathcal{R}(J/\ddot{I}ˆ)=0.51\pm 0.12\text{(stat)}\pm 0.08\text{(syst)}$, which is within 1.8 standard deviations of the predictions from the Standard Model assuming lepton flavor universality.

All figures and tables, along with any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/5430