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
Table1:PredictionsforthebranchingratiosoftheFCNCtopquarkdecays.TheTC2predictions
TC=0.4.TheMSSMpredictionsarethemaximalaretakenfromFig.3forMTC=300GeVandKUR
valuesintheallowedparameterspace.
MSSM
Br(t→cZ)O(10 7)[4]
Br(t→cγ)O(10 7)[4]
Br(t→cg)O(10 5)[4]
Br(t→cgg)O(10 4)[4]
2ag2sPL γργµγλ(Cρλ1+Cρλ2+2Cρλ3)+γργµk/(Cρ1+Cρ2+2Cρ3)
+mtγργµ( Cρ1+Cρ2)+mtγµγρ( Cρ1+Cρ2)+mtγµk/( C01+C02)
+m2tγµ( C01+C02)
iΣ(p1 t)=
2aPL[p/c(B41+B51+2B61)+mt( B40+B50)]
(A1)(A3)