Measurement of the ratio of branching fractions and difference in CP asymmetries of the decays B + → J/ ψπ + and B + → J/ ψK +

Abstract

The ratio of branching fractions and the difference in CP asymmetries of the decays B + → J/ψπ + and B + → J/ψK + are measured using a data sample of pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 3 fb-1 at centre-of-mass energies of 7 and 8 TeV. The results are B({B}+\to J/ψ {π}+)/B({B}+\to J/ψ {K}+)=(3.83± 0.03± 0.03)× {10}^{-2}, A^{CP}({B}+\to J/ψ {π}+)-A^{CP}({B}+\to J/ψ {K}+)=(1.82± 0.86± 0.14)× {10}^{-2}, where the first uncertainties are statistical and the second are systematic. Combining this result with a recent LHCb measurement of A^{CP}({B}+\to J/{ψ K}+) provides the most precise estimate to date of CP violation in the decay B + → J/ψπ +, A^{CP}({B}+\to J/{ψ π}+)=(1.91± 0.89± 0.16)× 1{0}^{-2}.