Direct Detection Constraints on Dark Photon Dark Matter

TL;DR

This paper establishes new, stringent constraints on dark photon dark matter in the 0.01-100 keV range using direct detection experiments, surpassing previous indirect bounds and exploring cosmological and astrophysical limits.

Contribution

It derives the most sensitive direct detection constraints on dark photon dark matter, improving upon existing bounds and analyzing cosmological and astrophysical limits.

Findings

Dark photon mixing angle constrained to ~10^{-15}

Direct detection limits surpass stellar energy loss bounds

Cosmological ionization limits are comparable to gamma-ray flux constraints

Abstract

Dark matter detectors built primarily to probe elastic scattering of WIMPs on nuclei are also precise probes of light, weakly coupled particles that may be absorbed by the detector material. In this paper, we derive constraints on the minimal model of dark matter comprised of long-lived vector states V (dark photons) in the 0.01-100 keV mass range. The absence of an ionization signal in direct detection experiments such as XENON10 and XENON100 places a very strong constraint on the dark photon mixing angle, down to $O(10^{-15})$, assuming that dark photons comprise the dominant fraction of dark matter. This sensitivity to dark photon dark matter exceeds the indirect bounds derived from stellar energy loss considerations over a significant fraction of the available mass range. We also revisit indirect constraints from $V\to 3\gamma$ decay and show that limits from modifications to the cosmological ionization history are comparable to the updated limits from the diffuse gamma-ray flux.