$h\to gg$ and $h\to\gamma\gamma$ with Anomalous Couplings at Next-to-Leading Order in QCD

TL;DR

This paper extends NLO QCD calculations for Higgs decay processes to include anomalous couplings, reducing uncertainties and improving the precision of Higgs coupling measurements within an effective field theory framework.

Contribution

It provides a systematic NLO QCD computation for Higgs decays with anomalous couplings using an electroweak chiral Lagrangian, clarifying the impact of QCD corrections.

Findings

QCD effects are large for h→gg and significantly reduce uncertainties at NLO.

QCD effects are mild for h→γγ, with NLO nearly eliminating uncertainties.

No new couplings appear at NLO beyond those at leading order.

Abstract

We generalize the next-to-leading order QCD calculations for the decay rates of $h\to gg$ and $h\to\gamma\gamma$ to the case of anomalous couplings of the Higgs boson. We demonstrate how this computation can be done in a consistent way within the framework of an electroweak chiral Lagrangian, based on a systematic power counting. It turns out that no additional coupling parameters arise at NLO in QCD beyond those already present at leading order. The impact of QCD is large for $h\to gg$ and the uncertainties from QCD are significantly reduced at NLO. $h\to\gamma\gamma$ is only mildly affected by QCD; here the NLO treatment practically eliminates the uncertainties. Consequently, our results will allow for an improved determination of anomalous Higgs couplings from these processes. The relation of our framework to a treatment in Standard Model effective field theory is also discussed.