Next-to-leading order QCD corrections to the top quark decay via model-independent FCNC couplings

TL;DR

This paper calculates next-to-leading order QCD corrections to top quark decay channels involving flavor-changing neutral currents, providing essential insights for experimental searches at Tevatron and LHC.

Contribution

It presents the first NLO calculations of top quark decay branching ratios via FCNC couplings, crucial for consistent interpretation of experimental limits.

Findings

NLO corrections to decay widths are about 10%.

Branching ratios are modified by approximately 20%, 0.4%, and 2%.

Results aid in experimental sensitivity studies at colliders.

Abstract

D0 and CDF collaborations at the Fermilab Tevatron have searched for non-standard-model single top-quark production and set upper limits on the anomalous top quark flavor-changing neutral current (FCNC) couplings $\kappa^g_{tc}/\Lambda$ and $\kappa^g_{tu}/\Lambda$ using the measurement of 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. We find that the NLO corrections to the partial decay widths of the three decay channels $ t\to q + g$, $ t\to q + \gamma$ and $ t\to q + Z$ are at the order of 10% in magnitude and modify their branching ratios by about 20%, 0.4% and 2%, respectively, as compared to their leading order predictions.