Abstract
This paper presents a combined analysis of the potential of a future electron-positron collider to constrain the Higgs, top, and electroweak sectors of the Standard Model effective field theory. The leading contributions of operators involving top quarks arise mostly at one-loop suppressed order and can be captured by the renormalization group mixing with Higgs operators. We perform global fits with an extended basis of 29 parameters, including both Higgs and top operators, to the projections for the Higgs, top, and electroweak precision measurements at the International Linear Collider (ILC). The determination of the Higgs boson couplings in the 250 GeV stage of the ILC is initially severely degraded by the additional top-quark degrees of freedom, but can be nearly completely recovered by the inclusion of precise measurements of top-quark EW couplings at the LHC. The physical Higgs couplings are relatively robust, as the top mass is larger than the energy scale of electroweak processes. The effect of the top operators on the bounds on the Wilson coefficients is much more pronounced and may limit our ability to identify the source of deviations from the Standard Model. Robust global bounds on all Wilson coefficients are only obtained when the 500 GeV stage of the ILC is included.
Highlights
With the discovery of the Higgs boson, all particles postulated by the Standard Model (SM) of particle physics have been experimentally confirmed
We focus on an electron-positron collider with sufficient energy to produce Higgs bosons and eventually top quarks, and adopt in particular the scenario1 of the International Linear Collider (ILC) [5,6]
The Higgs boson couplings are expected to deviate from the SM predictions as κ ∼ 1 − c × 1 TfeV, where f is the scale associated with the new physics and c ∼ 3% for vector boson couplings and c ∼ 3–9% for fermion couplings [22]
Summary
With the discovery of the Higgs boson, all particles postulated by the Standard Model (SM) of particle physics have been experimentally confirmed. Effective-field theory (EFT) or the Standard Model EFT (SMEFT) is a crucial tool in modern high-energy physics, as it provides a relatively model-independent framework to order and interpret the enormous wealth of measurements from experiments at colliders and elsewhere. It is important to include top contributions and assess whether the Higgs precision achievable without model-independent top effects can be retained even with them, what capabilities of future colliders are needed, and whether the top sector can be precisely constrained without direct top productions. To this end, we extend the previous SMEFT basis of Ref. VI, we summarize the most important findings of the study and discuss their implications
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