QCD Corrections to Flavor Changing Neutral Coupling Mediated Rare Top Quark Decays

TL;DR

This paper calculates next-to-leading order QCD corrections to rare top quark decays mediated by flavor-changing neutral currents, providing detailed analytical results and exploring implications for collider experiments.

Contribution

It offers a comprehensive calculation of QCD corrections to t-> q gamma and t-> q Z decays, including operator mixing and effects of kinematic cuts, advancing theoretical understanding of these processes.

Findings

QCD corrections significantly affect decay rates

t-> q gamma can probe t-> q g operators

Experimental signals of t-> q g imply lower bounds on t-> q gamma

Abstract

Recently we have presented an analysis of flavor changing neutral coupling mediated radiative top quark decays at next-to-leading order in QCD. In the present paper we provide the details of the calculation of QCD corrections to t-> q gamma and t-> q Z decays within the effective theory approach including operator mixing. In particular, we calculate virtual matrix element corrections and the corresponding bremsstrahlung contributions. In the case of t-> q gamma we study the effects of kinematic cuts on the extracted branching ratios. Analytical formulae are given at all stages of the calculation. We find that the t-> q gamma decay can be used to probe also the effective operators mediating t-> q g processes, since these can naturally contribute 10% or more to the radiative decay, given typical experimental cuts on the decay kinematics at hadron colliders. Conversely, we argue that any positive experimental signal of the t-> q g process would indicate a natural lower bound on t-> q gamma decay rate.