Cosmological Constraints on Very Dark Photons

TL;DR

This paper investigates how very dark photons with tiny electromagnetic couplings affect early universe processes, deriving new constraints on their properties based on cosmological observations.

Contribution

It provides the first detailed calculation of freeze-in production and late decay effects of dark photons in the specified mass and coupling range.

Findings

New bounds on dark photon mass and kinetic mixing parameter from cosmological data.

Constraints derived from effects on Big Bang Nucleosynthesis and the Cosmic Microwave Background.

Identification of parameter space where dark photons could exist without conflicting with observations.

Abstract

We explore the cosmological consequences of kinetically mixed dark photons with a mass between 1 MeV and 10 GeV, and an effective electromagnetic fine structure constant as small as $10^{-38}$. We calculate the freeze-in abundance of these dark photons in the early Universe and explore the impact of late decays on BBN and the CMB. This leads to new constraints on the parameter space of mass $m_V$ vs kinetic mixing parameter $\kappa$.