Kinetic Mixing, Dark Photons and Extra Dimensions II: Fermionic Dark Matter

Understand

Extra dimensions can be very useful tools when constructing new physics models.

• Previously, we began investigating toy models for the 5-D analog of the kinetic mixing/vector portal scenario where the interactions of bulk dark matter with the brane-localized fields of the Standard Model are mediated by a massive $U(1)_D$ dark photon also living in the bulk.
• In that setup, where the dark matter was taken to be a complex scalar, a number of nice features were obtained such as $U(1)_D$ breaking by boundary conditions without the introduction of a dark Higgs field, the absence of potentially troublesome SM Higgs-dark singlet mixing, also by boundary conditions, the natural similarity of the dark matter and dark photon masses and the decoupling of the heavy gauge Kaluza-Klein states from the Standard Model.
• In the present paper we extend this approach by examining the more complex cases of Dirac and Majorana fermionic dark matter.