Experimental targets for dark photon dark matter

TL;DR

This paper investigates the conditions under which dark photon dark matter can form without disrupting early-Universe dynamics, proposing new models and experimental targets to detect or constrain such scenarios.

Contribution

It identifies the parameter space where dark photon production is viable, avoiding backreaction issues, and introduces novel models with specific experimental and observational signatures.

Findings

Certain parameter regions allow dark photon dark matter without backreaction.

New models set targeted experimental searches across accessible parameter space.

Cosmological and astrophysical signatures can probe dark sector physics.

Abstract

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. We establish the general conditions under which dark photon production avoids significant backreaction on the dark Higgs and identify regions of parameter space that naturally circumvent these constraints. After surveying implications for known dark photon production mechanisms, we propose novel models that set well-motivated experimental targets across much of the accessible parameter space. We also discuss complementary cosmological and astrophysical signatures that can probe the dark sector physics responsible for dark photon production.