Estimates of the weak annihilation contributions to the decays B → ϱ + γ and B → ω + γ

The dominant long-distance contributions to the exclusive radiative decays B → ϱ(ω) + γ involve photon emission from light quarks at large distances, which cannot be treated perturbatively. We point out that this emission can be described in a theoretically consistent way as the magnetic excitation of quarks in the QCD vacuum and estimate the corresponding parity-conserving and parity-violating amplitudes using the light-cone QCD sum-rule approach. These are then combined with the corresponding short-distance contribution from the magnetic moment operator in the same approach, derived earlier, to estimate the decay rates Γ(B → ϱ(ω) + γ). The implications of this result for the determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements in radiative B decays are worked out.