Making dark matter out of light: freeze-in from plasma effects

Abstract

Dark matter (DM) could couple to particles in the Standard Model (SM) through a light vector mediator. In the limit of small coupling, this portal could be responsible for producing the observed DM abundance through a mechanism known as freeze-in. Furthermore, the requisite DM-SM couplings provide a concrete benchmark for direct and indirect searches for DM. In this paper, we present updated calculations of the relic abundance for DM produced by freeze-in through a light vector mediator. We identify an additional production channel: the decay of photons that acquire an in-medium plasma mass. These plasmon decays are a dominant channel for DM production for sub-MeV DM masses, and including this channel leads to a significant reduction in the predicted signal strength for DM searches. Accounting for production from both plasmon decays and annihilations of SM fermions, the DM acquires a highly non-thermal phase space distribution which impacts the cosmology at later times; these cosmological effects will be explored in a companion paper.

23+8 pages, 8+1 figures

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Cited by in corpus (10)

• Refined Bounds on MeV-scale Thermal Dark Sectors from BBN and the CMB
• How warm are non-thermal relics? Lyman-$\alpha$ bounds on out-of-equilibrium dark matter
• Probing dark photons with plasma haloscopes
• Freeze-in produced dark matter in the ultra-relativistic regime
• Dark Matter Abundance from Sequential Freeze-in Mechanism
• Dark Matter, Dark Photon and Superfluid He-4 from Effective Field Theory
• Structure Formation and the Global 21-cm Signal in the Presence of Coulomb-like Dark Matter-Baryon Interactions
• The Milky Way, Coming into Focus: Precision Astrometry Probes its Evolution, and its Dark Matter
• The Hierarchy Problem: From the Fundamentals to the Frontiers
• Dark matter scattering in astrophysical media: collective effects