Topcolor-Assisted Technicolor and the Decay Bc → Ds*γ

Applying the perturbative QCD method, we study the process B_c → D_s^*γ in the topcolor-assisted technicolor model (TATCM), and compare the results with those estimated in the standard model (SM). There are two mechanisms which contribute to the B_c → D_s^*γ process. One proceeds through the short distance b → sγ transition, the other through weak annihilation accompanied by a photon emission. The contribution of weak annihilation is found to be much more important than that of tlie electromagnetic penguin in the TATCM, and the branching ratio, BR (B_c → D_s^*γ), is much smaller than that in the SM.