Stokes vector of photon in the decays B0→ρ0γ and [formula omitted

Abstract

We consider a model for the decay B0→ρ0γ in which the short-distance amplitude determined by the Hamiltonian describing b→dγ is combined with a typical long-distance contribution B0→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 B0→ρ0γ∗→π+π−e+e− where they produce a characteristic effect in the angular distribution dΓ/dφ, φ being the angle between the π+π− and e+e− planes. A similar analysis is carried out for the decays B0→K∗γ and B0→K∗γ∗→π+K−e+e−.