Measurement of the ratio of branching fractions ℬ(Bc+→J/^ψK+)/ℬ(Bc+→J/^ψπ+)

The ratio of branching fractions RK/π≡ℬ(Bc+→J/ψK+)/ℬ(Bc+→J/ψπ+) 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 fb ⁻¹. It is found to be R _K/π = 0.079 ± 0.007 ± 0.003, 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.[Figure not available: see fulltext.]