D0 and CDF collaborations at the Fermilab Tevatron have searched for nonstandard-model single top-quark production and have set upper limits on the anomalous top-quark flavor-changing neutral-current (FCNC) couplings ${\kappa }_{\mathrm{tc}}^g/\Lambda$ and ${\kappa }_{\mathrm{tu}}^g/\Lambda$ using the measurement of the total cross section calculated at the next-to-leading order (NLO) in QCD. In this Letter, we report on the effect of anomalous FCNC couplings to various decay branching ratios of the top quark, calculated at the NLO. This result is not only mandatory for a consistent treatment of both the top-quark production and decay via FCNC couplings by D0 and CDF at the Tevatron, but is also important for the study of ATLAS and CMS sensitivity to these anomalous couplings at the CERN LHC.

• Received 4 November 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.072001