Stealth decaying spin-1 dark matter

TL;DR

This paper introduces a model of decaying spin-1 dark matter interacting via a dark-Higgs portal, which can account for observed dark matter abundance while evading current experimental constraints.

Contribution

It proposes a novel dark matter model with slow decay channels and relic abundance set by freeze-in, compatible with natural parameters and a specific mass range.

Findings

Dark matter mass range of ~5 keV to 1 MeV fits observations.

Model evades constraints from detection and cosmology.

Nonzero kinetic mixing has mild phenomenological impact.

Abstract

We consider models of decaying spin-1 dark matter whose dominant coupling to the standard model sector is through a dark-Higgs Yukawa portal connecting a TeV-scale vector-like lepton to the standard model (right-handed) electron. Below the electron-positron threshold, dark matter has very slow, loop-suppressed decays to photons and (electron) neutrinos, and is stable on cosmological time-scale for sufficiently small gauge coupling values. Its relic abundance is set by in-equilibrium dark lepton decays, through the freeze-in mechanism. We show that this model accommodates the observed dark matter abundance for natural values of its parameters and a dark matter mass in the ~5keV to 1MeV range, while evading constraints from direct detection, indirect detection, stellar cooling and cosmology. We also consider the possibility of a nonzero gauge kinetic mixing with the standard model hypercharge field, which is found to yield a mild impact on the model's phenomenology.