Impact of NLO EW and QCD corrections to dimension-6 SMEFT coefficients constraints in Higgs decays

This paper presents the impact of the inclusion of next-to-leading-order (NLO) QCD and electroweak (EW) corrections for dimension-6 Standard Model Effective Field Theory (SMEFT) predictions for the Higgs decays in Higgs couplings measurements at the Large Hadron Collider. Such higher-order corrections will be increasingly important for the precise Higgs and electroweak measurements expected at the High-Luminosity Large Hadron Collider (HL-LHC). The results are compared with a SMEFT parameterisation employing inputs from a previous ATLAS study, in which the dimension-6 SMEFT contributions are evaluated for each production and decay process at the lowest non-vanishing perturbative QCD order of the corresponding SM process. The effects of the SMEFT NLO QCD/EW contributions to the Higgs decay channels are largest for 2-fermion operators involving the third generation. The sensitivity to the Higgs tri-linear coupling is also explored.