Study of B±→J/ψπ± and B±→J/ψK± decays:: Measurement of the ratio of branching fractions and search for direct CP violation -: art. no. 241802

We study B+/--->J/psipi(+/-) and B+/--->J/psiK(+/-) decays in a sample of about 89x10(6) B (B) over bar pairs collected with the BABAR detector at the PEP-II asymmetric B factory at SLAC. We observe a signal of 244+/-20 B+/--->J/psipi(+/-) events and determine the ratio B(B+/--->J/psipi(+/-))/B(B+/--->J/psiK(+/-)) to be [5.37+/-0.45(stat)+/-0.11(syst)]%. The charge asymmetries for the B+/--->J/psipi(+/-) and B+/--->J/psiK(+/-) decays are determined to be A(pi)=0.123+/-0.085(stat)+/-0.004(syst) and A(K)=0.030+/-0.015(stat)+/-0.006(syst), respectively.