When Two Loops Matter: Electroweak Precision in the SMEFT

TL;DR

This paper uncovers a significant two-loop order effect in the SMEFT that impacts electroweak precision tests, especially relevant for future high-precision colliders, linking top-Higgs interactions to W mass shifts.

Contribution

It identifies a novel two-loop renormalization effect in SMEFT that influences electroweak precision observables and is crucial for interpreting future collider data.

Findings

Two-loop order effect significantly shifts W mass via top-Higgs coupling modifications.

Electroweak precision observables can indirectly probe top-Higgs interactions.

Effect demonstrated in a simple two-Higgs doublet model.

Abstract

We identify a novel next-to-leading order renormalization effect in the dimension-six SMEFT with direct phenomenological impact. The Higgs-Yukawa operator that modifies the top-Higgs coupling $\kappa_t$ induces a shift in the $ W $ mass at two-loop order through a large anomalous dimension, rendering electroweak precision observables a powerful indirect probe of $\kappa_t$. We show that this effect is essential for the consistent interpretation of data from future Tera-$Z$ and Giga-$W$ factories such as FCC-ee. The effect is realized in a simple renormalizable two-Higgs doublet model.