Abstract
The calculation of next-to-leading order (NLO) perturbative corrections at fixed operator dimension in Standard Model Effective Field Theory (SMEFT) has been a topic of much recent interest. In this paper we obtain the NLO corrections from dimension-6 operators to the Higgs boson decays hto foverline{f} , where the fermions f ∈ {μ, τ, c}. This extends previous results for hto boverline{b} to all phenomenologically relevant Higgs boson decays into fermions, and provides the basis for future precision analyses of these decays within effective field theory. We point out the benefits of studying ratios of decay rates into different fermions in SMEFT, the most surprising of which is enhanced sensitivity to anomalous hγγ and hgg couplings induced by flavor-universal SMEFT operators, especially in scenarios where flavor-dependent Wilson coefficients are constrained by Minimal Flavor Violation.
Highlights
We point out the benefits of studying ratios of decay rates into different fermions in Standard Model Effective Field Theory (SMEFT), the most surprising of which is enhanced sensitivity to anomalous hγγ and hgg couplings induced by flavor-universal SMEFT operators, especially in scenarios where flavor-dependent Wilson coefficients are constrained by Minimal Flavor Violation
This pattern holds in general: the SMEFT Lagrangian in terms of mass-basis fermion fields and Wilson coefficients is obtained by interpreting the fermion fields in the list of operators table 3 to be in the mass basis, and multiplying it with a corresponding mass-basis Wilson coefficient, which can be related to the weak-basis one through rotations such as eq (3.4)
It is a poor approximation to estimate next-to-leading order (NLO) corrections to the dimension-6 operators appearing in the LO result by assuming they are proportional to the NLO correction in the SM
Summary
We outline the procedure used to obtain the NLO corrections to the decay rates h → f f, with h the Higgs boson and f a fermion, in dimension-6 SMEFT. Contributions from heavy-particle loops depending on mEW appear in Γ(fi,,w1e)ak through decoupling constants for mf and α; these pieces are effectively calculated in the on-shell scheme, where tadpoles cancel between different terms in the decay rate, so enhanced EW corrections scaling as m4t /m2H v2 (where v is defined in eq (4.1) below) due to these tadpoles are absent. The same is not true of Γ(fi,,w1e)ak These weak corrections receive flavor-dependent contributions from a large set of one-loop diagrams entering mass renormalization, the decoupling constants, and the bare one-loop matrix elements, which we must calculate from scratch. To this end, we have altered the in-house code developed to automate the one-loop h → bb calculation [42]. We calculate the weak corrections in both Feynman and unitary gauge, check the cancellation of UV and IR poles in the dimensional regulator, and make sure that the decay rate is independent of unphysical renormalization scales up to NLO
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