Measurement of the ratio of branching fractions $mathcal{B}(B_{c}^{+} to J/psi K^{+})/mathcal{B}(B_{c}^{+} to J/psipi^{+})$

The ratio of branching fractions $R_{K/pi} equiv mathcal{B}(B_{c}^{+} to J/psi K^{+})/mathcal{B}(B_{c}^{+} to J/psipi^{+})$ is measured with $pp$ collision data collected by the LHCb experiment at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 3${mbox{fb}^{-1}}$. It is found to be $ R_{K/pi} = 0.079pm0.007pm0.003$, where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the previous LHCb result, while the uncertainties are significantly reduced.