Stokes vector of photon in the decays B0→ρ0γ and B0→K*γ

We consider a model for the decay B-bar0→ρ0γ in which the short-distance amplitude determined by the Hamiltonian describing b→dγ is combined with a typical long-distance contribution B-bar0→D+D-→ρ0γ. The latter possesses a significant dynamical phase which induces a CP-violating asymmetry ACP, as well as an important modification of the Stokes vector of the photon. The components S1 and S3 of the Stokes vector S→=(S1,S2,S3) can be measured in the decay B-bar0→ρ0γ*→π+π-e+e- where they produce a characteristic effect in the angular distribution dΓ/dphi, phi being the angle between the π+π- and e+e- planes. A similar analysis is carried out for the decays B-bar0→K-bar0γ and B-bar0→K-bar*γ*→π+K-e+e-