Constraints on scattering of keV--TeV dark matter with protons in the early Universe

TL;DR

This paper uses Planck CMB data to set the first comprehensive cosmological constraints on keV to TeV dark matter scattering with protons, significantly improving previous limits and covering low-mass dark matter candidates.

Contribution

It provides the first cosmological constraints across the entire 1 keV to 1 TeV mass range for dark matter-proton scattering, including both spin-independent and spin-dependent interactions.

Findings

Excludes spin-independent cross sections above 5.3e-27 cm^2 at 1 keV

Improves constraints by orders of magnitude over previous limits

Covers the low-mass dark matter regime down to 1 keV

Abstract

We present the first cosmological constraint on dark matter scattering with protons in the early Universe for the entire range of dark matter masses between 1 keV and 1 TeV. This constraint is derived from the Planck measurements of the cosmic microwave background (CMB) temperature and polarization anisotropy, and the CMB lensing anisotropy. It improves upon previous CMB constraints by many orders of magnitude, where limits are available, and closes the gap in coverage for low-mass dark matter candidates. We focus on two canonical interaction scenarios: spin-independent and spin-dependent scattering with no velocity dependence. Our results exclude (with 95% confidence) spin-independent interactions with cross sections greater than $5.3 \times 10^{-27}$ cm$^2$ for 1 keV, $3.0 \times 10^{-26}$ cm$^2$ for 1 MeV, $1.7 \times 10^{-25}$ cm$^2$ for 1 GeV, and $1.6 \times 10^{-23}$ cm$^2$ for 1 TeV dark matter mass. Finally, we discuss the implications of this study for dark matter physics and future observations.