Determination of the strong g-coupling and of the mu(B*B gamma)-strength from two-photon decays of heavy vector mesons

We describe a calculation of the two-photon decays of heavy vector-mesons, B^* → Bγγ and D^* → Dγγ, by using the "heavy meson chiral Lagrangian". The decay amplitudes are expressed in terms of the strong coupling g of the Lagrangian at various powers and the strength of the anomalous magnetic dipole μ_{B* Bγ} (respectively μ_{D* D}γ). In the charm case we are able to express the branching ratio Γ(D^*0 → D⁰γγ)/Γ(D^*0) as a function of g only and we expect it to be in the 10^-6 - 10^-5 range, depending on the value of g. The determination of μ_{B*0 B}⁰_γ, μ_B*+B+γ requires a more involved analysis, including the consideration of bremsstrahlung radiation for the B^*+ → B⁺γγ case.