Measurement of the ratio of branching fractions B(B-+/- -> J/psi pi(+/-))/B(B-+/- -> J/psi K-+/-)

We report a measurement of the ratio of branching fractions of the decays B-+/- -> J/psi pi(+/-) and B-+/- -> J/psi K-+/- using the CDF II detector at the Fermilab Tevatron Collider. The signal from the Cabbibo-suppressed B-+/- -> J/psi pi(+/-) decay is separated from B-+/- -> J/psi K-+/- using the B-+/- -> J/psi K-+/- invariant mass distribution and the kinematical differences of the hadron track in the two decay modes. From a sample of 220 pb(-1) of p (p) over bar collisions at root s = 1.96 TeV, we observe 91 +/- 15 B-+/- -> J/psi pi(+/-) events together with 1883 +/- 34 B-+/- -> J/psi K-+/- events. The ratio of branching fractions is found to be B(B-+/- -> J/psi pi(+/-))/B(B-+/- -> J/psi K-+/-) = (4.86 +/- 0.82(stat) +/- 0.15(syst))%. RI Ruiz, Alberto/E-4473-2011; Robson, Aidan/G-1087-2011; De Cecco, Sandro/B-1016-2012; St.Denis, Richard/C-8997-2012; Prokoshin, Fedor/E-2795-2012; Azzi, Patrizia/H-5404-2012