Astrophysical aspects of milli-charged dark matter in a Higgs-Stueckelberg model

An extension of the Standard Model is studied, in which two new vector bosons are introduced, a first boson $Z^{\mathrm{\prime }}$ coupled to the SM by the usual minimal coupling, producing an enlarged gauge sector in the SM. The second boson $A^{\mathrm{\prime }}$ field, in the dark sector of the model, remains massless and originates a dark photon ${\gamma }^{\mathrm{\prime }}$. A hybrid mixing scenario is considered based on a combined Higgs and Stueckelberg mechanisms. In a Compton-like process a photon scattered by a WIMP is converted into a dark photon. This process is studied, in an astrophysical application obtaining an estimate of the impact on stellar cooling of white dwarfs and neutron stars.