Measurements of the branching fractions and helicity amplitudes in B⃗D*ρ decays

Using 9.1fb^-1 of e⁺e^- data collected at the Υ(4S) with the CLEO detector using the Cornell Electron Storage Ring, measurements are reported for both the branching fractions and the helicity amplitudes for the decays B^-→D^*0ρ^- and B⁰→D^*+ρ^-. The fraction of longitudinal polarization in B⁰→D^*+ρ^- is found to be consistent with that in B⁰→D^*+l^-ν̅ at q²=M_ρ², indicating that the factorization approximation works well. The longitudinal polarization in the B^- mode is similar. The measurements also show evidence of nontrivial final-state interaction phases for the helicity amplitudes.