Experimental targets for dark photon dark matter

Understand

Ultralight dark photon dark matter features distinctive cosmological and astrophysical signatures and is also supported by a burgeoning direct-detection program searching for its kinetic mixing with the ordinary photon over a wide mass range.

• Dark photons, however, cannot necessarily constitute the dark matter in all of this parameter space.
• In minimal models where the dark photon mass arises from a dark Higgs mechanism, early-Universe dynamics can easily breach the regime of validity of the low-energy effective theory for a massive vector field.
• In the process, the dark sector can collapse into a cosmic string network, precluding dark photons as viable dark matter.