Measurements of Branching Fractions, Polarizations, and Direct CP-Violation Asymmetries in B→ρK* and B→f0(980)K* Decays

We report searches for B-meson decays to the charmless final states ρK* and f0(980)K* with a sample of 232×10^6 BB̅ pairs collected with the BABAR detector at the PEP-II e+e- collider. We measure in units of 10-6 the following branching fractions, where the first error quoted is statistical and the second systematic, or upper limits are given at the 90% confidence level : B(B+→ρ0K*+)<6.1, B(B+→ρ+K*0)=9.6±1.7±1.5, B(B0→ρ-K*+)<12.0, B(B0→ρ0K*0)=5.6±0.9±1.3, B(B+→f0(980)K*+)=5.2±1.2±0.5, and B(B0→f0(980)K*0)<4.3. For the significant modes, we also measure the fraction of longitudinal polarization and the charge asymmetry: fL(B+→ρ+K*0)=0.52±0.10±0.04, fL(B0→ρ0K*0)=0.57±0.09±0.08, ACP(B+→ρ+K*0)=-0.01±0.16±0.02, ACP(B0→ρ0K*0)=0.09±0.19±0.02, and ACP(B+→f0(980)K*+)=-0.34±0.21±0.03.