Dark Mater Interactions From An Extra U(1) gauge symmetry with kinetic mixing and Higgs charge

TL;DR

This paper explores how an extra U(1) gauge symmetry with kinetic mixing and Higgs charge affects fermionic dark matter interactions, potentially reducing detection cross sections and increasing relic density.

Contribution

It introduces a model with Higgs charge under U(1)_X, showing how it can suppress direct detection signals and enhance dark matter relic density, expanding viable parameter space.

Findings

Higgs charge reduces dark matter-nucleon scattering cross section.

Higgs charge can increase dark matter relic density significantly.

Resonance effects help reconcile relic density with detection constraints.

Abstract

We investigate fermionic dark matter interactions with standard model particles from an additional $\mathrm{U}(1)_\mathrm{X}$ gauge symmetry, assuming kinetic mixing between the $\mathrm{U}(1)_\mathrm{X}$ and $\mathrm{U}(1)_\mathrm{Y}$ gauge fields as well as a nonzero $\mathrm{U}(1)_\mathrm{X}$ charge of the Higgs doublet. For ensuring gauge-invariant Yukawa interactions and the cancellation of gauge anomalies, the standard model fermions are assigned $Y$-sequential $\mathrm{U}(1)_\mathrm{X}$ charges proportional to the Higgs charge. Although the Higgs charge should be small due to collider constraints, it is useful to decrease the effective cross section of dark matter scattering off nucleons by two orders of magnitude and easier evade from direct detection bounds. After some numerical scans performed in the parameter space, we find that the introduction of the Higgs charge can also enhance the dark matter relic density by at least two orders of magnitude. When the observed relic density and the direct detection constraints are tangled, at the case where the resonance effect is important for dark matter freeze-out, the Higgs charge can expand physical windows to some extent by relieving the tension between the relic density and the direct detection.