EWPD in the SMEFT to dimension eight

Understand

We calculate the $\mathcal{O}(\langle H^{\dagger} H \rangle^{2} / \Lambda^{4} )$ corrections to LEP electroweak precision data using the geometric formulation of the Standard Model Effective Field Theory (SMEFT).

• We report our results in simple-to-use interpolation tables that allow the interpretation of this data set to dimension eight for the first time.
• We demonstrate the impact of these previously unknown terms in the case of a general analysis in the SMEFT, and also in the cases of two distinct models matched to dimension eight.
• Neglecting such dimension-eight corrections to LEP observables introduces a theoretical error in SMEFT studies.