New Limits on Light Dark Matter-Nucleon Scattering

TL;DR

This paper establishes new, stringent bounds on sub-GeV dark matter interactions with nucleons, using Big Bang Nucleosynthesis, chiral perturbation theory, and rare Kaon decays, impacting future detection efforts.

Contribution

It introduces novel constraints on light dark matter-nucleon scattering by combining cosmological and particle physics analyses, including one-loop photon interactions and rare decay bounds.

Findings

One-loop photon interactions can equilibrate dark matter and Standard Model sectors at MeV temperatures.

Derived upper bounds on dark matter-nucleon cross-sections are much stronger than previous astrophysical limits.

Rare Kaon decay data provide additional, tighter constraints on light dark matter interactions.

Abstract

We derive new bounds on hadronically-interacting, sub-GeV mass dark matter. First, we show that one-loop interactions with photons can be sufficient to maintain equilibrium between the dark matter and Standard Model sectors at MeV temperatures, resulting in constraints from Big Bang Nucleosynthesis. Using chiral perturbation theory, we find that this leads to an upper bound on the dark-matter--nucleon scattering cross-section that is orders of magnitude stronger than existing astrophysical constraints. Furthermore, we show that even if these interactions remain out of equilibrium, there is an irreducible freeze-in abundance of dark matter that can easily overclose the universe. We also compute new bounds from rare Kaon decays that can provide even stronger constraints. Our results have significant implications for future direct detection experiments aiming to search for MeV-scale dark matter.