Measurement of the branching fraction B(B-u(+)->J/psi pi(+)) and search for B-c(+)->J/psi pi(+)

We report on a measured of the branching fraction of the Cabibbo-suppressed decay B-u(+)-->J/psi pi(+), where J/psi-->mu(+)mu(-). The data were collected by the Collider Detector at Fermilab during 1992-1995 and correspond to an integrated luminosity of 110 pb(-1) in (p) over tildep$ collisions at root s=1.8 TeV. A signal of 28(-9)(+10) events is observed and we demonstrate the ratio of branching fractions B(B-u(+)-->J/psi pi)/B(B-u(+)-->J/psi K+) to be [5.0(-1.7)(+1.9) (stat)+/-0.1(syst)]%. Using the world average value for B(B-u(+)-->J/psi K+), we calculate the branching fraction B(B-u(+)-->J/psi pi(+)) to be (5.0(-1.9)(+2.1))x10(-5). We also search for the decay B-c(+)-->J/psi pi(+) and report a 95% confidence level limit on sigma(B-c(+))B(B-c(+)-->J/psi pi(+)/sigma(B-u(+))B(B-u(+)-->J/psi K+) as a function of the B-c(+) lifetime.