Measurements of branching fractions for B+→ρ+γ, B0→ρ0γ, and B0→ωγ

We present branching fraction measurements for the radiative decays B+→ρ+γ, B0→ρ0γ, and B0→ωγ. The analysis is based on a data sample of 465×106 BB̅ events collected with the BABAR detector at the PEP-II asymmetric-energy B Factory located at the Stanford Linear Accelerator Center. We find B(B+→ρ+γ)=(1.20-0.37+0.42±0.20)×10-6, B(B0→ρ0γ)=(0.97-0.22+0.24±0.06)×10-6, and a 90% C.L. upper limit B(B0→ωγ)<0.9×10-6, where the first error is statistical and the second is systematic. We also measure the isospin-violating quantity Γ(B+→ρ+γ)/2Γ(B0→ρ0γ)-1=-0.43-0.22+0.25±0.10.