Top-Quark FCNC Decay t->cgg in Topcolor-assisted Technicolor Model

The topcolor-assisted technicolor (TC2) model predicts several pseudo-scalars called top-pions and at loop level they can induce the FCNC top quark decay t->cgg which is extremely suppressed in the Standard Model (SM). We find that in the allowed parameter space the TC2 model can greatly enhance such a FCNC decay and push the branching ratio up to 10^{-3}, which is much larger than the predictions in the SM (10^{-9}) and in the minimal supersymmetric model (10^{-4}). We also compare the result with the two-body FCNC decay t-> cg and find that the branching ratio of t-> cgg is slightly larger than t-> cg. Such enhanced FCNC top quark decays may serve as a good probe of TC2 model at the future top quark factory.Comment: 11 pages, 4 figure