Branching fraction and charge asymmetry measurements in B→J/ψππ decays

We study the decays B-0 -> J/psi pi(+)pi(-) and B+-> J/psi pi(+)pi(0), including intermediate resonances, using a sample of 382x10(6) B (B) over bar pairs recorded by the BABAR detector at the PEP-II e(+)e(-) B factory. We measure the branching fractions B(B-0 -> J/psi rho(0))=(2.7 +/- 0.3 +/- 0.2)x10(-5) and B(B+-> J/psi rho(+))=(5.0 +/- 0.7 +/- 0.3)x10(-5). We also set the following upper limits at the 90% confidence level: B(B-0 -> J/psi pi(+)pi(-) nonresonant)< 1.2x10(-5), B(B-0 -> J/psi f(2))< 4.6x10(-6), and B(B+-> J/psi pi(+)pi(0) nonresonant)< 7.3x10(-6). We measure the charge asymmetry in charged B decays to J/psi rho to be -0.11 +/- 0.12 +/- 0.08.