A study on the rare radiative decay Bc → Ds∗γ

We study the decay Bc → Ds∗γ. There are two mechanisms contributing to the process. One proceeds through the short distance b → sγ transition and the other occurs through weak annihilation accompanied by a photon emission. The electromagnetic penguin contribution is estimated by perturbative QCD and found to be 4.68 × 10−18 GeV. In particular, we find the contribution of the weak annihilation is 6.25 × 10−18 GeV which is in the same order as that of the electromagnetic penguin. The total decay rate Γ(Bc → Ds∗γ) is predicted to be 1.45 × 10−17 GeV and the branching ratio Br(Bc → Ds∗γ) is predicted to be 2.98 × 10−5 for τBc = 1.35 ps. The the decays Bc → Ds∗γ can be well studied at LHC i the near future.