Top-quark decay into Higgs boson and a light quark at next-to-leading order in QCD

TL;DR

This paper calculates the next-to-leading order QCD corrections to the rare top-quark decay into a Higgs boson and a light quark, enhancing theoretical precision and understanding operator mixing in new physics scenarios.

Contribution

It provides the first NLO QCD calculation of t->u_i h decay including dimension-six operators, revealing the significance of the chromomagnetic operator.

Findings

NLO corrections are comparable to standard QCD corrections.

Operator mixing under renormalization is characterized.

Improved theoretical predictions for rare top decays.

Abstract

Neutral flavor-changing transitions are hugely suppressed in the Standard Model and therefore they are very sensitive to new physics. We consider the decay rate of t->u_i h where u_i=u,c using an effective field theory approach. We perform the calculation at NLO in QCD including the relevant dimension-six operators. We find that at NLO the contribution from the flavor-changing chromomagnetic operator is as important as the standard QCD correction to the flavor-changing Yukawa coupling. In addition to improving the accuracy of the theoretical predictions, the NLO calculation provides information on the operator mixing under the renormalization group.