Anomalous Wtb Couplings and b → sγ in the Topcolor Assisted Technicolor Models

Using the topcolor-assisted technicolor models, we give the anomalous Wtb couplings arising from the exchange of the new gauge bosons (ETC gauge boson, colorons and Z') and calculate their contributions to the b → sγ branching ratio. We find that the contributions mainly come from colorons and the recent measured value of the b → sγ branching ratio gives a strong constraint on the masses of colorons.