Higgs Model Coupled to Dark Photons

A dark sector containing a Higgs field and a dark photon coupled to visible photons via a small kinetic mixing is considered. The mass of the dark gauge boson becomes rescaled by the parameter involved in the kinetic mixing. We also calculate the total annihilation cross section for scalar Higgs interacting with an external field and show that exhibits Sommerfeld enhancement. The model can be extended to a $SU(3)\times SU(2)\times U(1)$ dark sector. The mass of the dark $Z$ boson increases due to the kinetic mixing.