Exploring Abelian–non-Abelian kinetic mixing in SMEFT and beyond

We explore a novel scenario involving Abelian–non-Abelian kinetic mixing within the framework of the Standard Model effective field theory (SMEFT) and its extension with a real triplet scalar field. In SMEFT, this mixing arises exclusively from a dimension-6 operator involving the Standard Model Higgs doublet, while the real triplet scalar field introduces an additional dimension-5 operator. We derive the modifications to electroweak gauge boson properties and impose constraints using electroweak precision data. In SMEFT, we find that Z-pole data at the Large Electron–Positron Collider imposes a stringent constraint on the kinetic mixing parameter, requiring it to be less than O(10−4), which corresponds to a new physics scale of about 10 TeV. In the SMEFT+triplet scenario, the constraint can be significantly relaxed with a sizeable triplet vacuum expectation value while preserving custodial symmetry in a finely tuned parameter space. Future measurements from the Circular Electron Positron Collider could probe the kinetic mixing parameter down to an order of magnitude smaller. Constraints from the Higgs signal strength data, Bs→μ+μ−, and muon (g−2) are also discussed. Published by the American Physical Society 2025