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 is reported of the ratio of branching fractions $\mathcal{R}(J/\ddot{I}ˆ)=\mathcal{B}(B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{„}^{+}\hat{I}{½}_{\ddot{I}}„)/\mathcal{B}(B_c^{+}\to J/\ddot{I}ˆ\hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)$, where the $\ddot{I}{„}^{+}$ lepton is identified in the decay mode $\ddot{I}{„}^{+}\to \hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼\overline{\hat{I}}{½}_{\ddot{I}}„$. This analysis uses a sample of proton-proton collision data corresponding to 3.0${\mathrm{fb}}^{-1}$ of integrated luminosity recorded with the LHCb experiment at center-of-mass energies $7\mathrm{TeV}$ and $8\mathrm{TeV}$. A signal is found for the decay $B_c^{+}\to J/\ddot{I}ˆ\ddot{I}{„}^{+}\hat{I}{½}_{\ddot{I}}„$ at a significance of 3 standard deviations, corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be $\mathcal{R}(J/\ddot{I}ˆ)=0.71\pm 0.17(\mathrm{stat})\pm 0.18(\mathrm{syst})$. This result lies within 2 standard deviations above the range of existing predictions in the Standard Model.

All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2017-035.html