BBN constraints on MeV-scale dark sectors. Part I. Sterile decays

TL;DR

This paper investigates how MeV-scale particles in a dark sector, especially those decaying into dark radiation, affect Big Bang Nucleosynthesis predictions and constrains models of self-interacting dark matter.

Contribution

It provides new constraints on MeV-scale dark sector particles decaying into dark radiation based on BBN, including cases with particles that are semi-relativistic during nucleosynthesis.

Findings

Constraints on dark sector particle properties from BBN.

Implications for self-interacting dark matter models.

Analysis of semi-relativistic particle decays during BBN.

Abstract

We study constraints from Big Bang Nucleosynthesis on inert particles in a dark sector which contribute to the Hubble rate and therefore change the predictions of the primordial nuclear abundances. We pay special attention to the case of MeV-scale particles decaying into dark radiation, which are neither fully relativistic nor non-relativistic during all temperatures relevant to Big Bang Nucleosynthesis. As an application we discuss the implications of our general results for models of self-interacting dark matter with light mediators.