Direct detection constraints on dark photon dark matter

Abstract

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