Electroweak Precision Constraints on Dark Photon Models with Generalized Mixing

TL;DR

This paper performs a comprehensive analysis of electroweak precision data to constrain dark photon models with generalized mixing, considering both kinetic and mass mixing effects from an extended scalar sector.

Contribution

It introduces a detailed global fit framework for dark photon models with generalized mixing, including tree-level and loop corrections from an extended Higgs sector.

Findings

Large parameter regions remain unconstrained by current data.

Dark photon masses between 40 GeV and 1 TeV are excluded for certain scalar VEV ratios.

Limits depend strongly on the scalar sector's vacuum expectation values.

Abstract

We present a global fit to electroweak precision observables (EWPOs) in dark photon (DP) models containing both kinetic and mass mixing between the DP and the neutral gauge bosons of the Standard Model (SM). Such more general mixing can be the result of an extended scalar sector, which we specify in this paper. We calculate the tree-level contributions to EWPOs due to the mixing with the DP, as well as the leading loop corrections to the oblique parameters due to the extended Higgs sector. In the scalar sector, we find that ample regions of parameter space are still unconstrained by data. In the gauge sector, the excluded region depends strongly on the vacuum expectation values of the scalar fields: for moderate ratios, DP masses in the $(40\,\text{GeV}, 1\,\text{TeV})$ range are excluded; for larger ratios, the limits become indistinguishable from those for standard DPs.