Towards Closing the Window on Strongly Interacting Dark Matter: Far-Reaching Constraints from Earth's Heat Flow

TL;DR

This paper introduces a new, largely model-independent constraint on strongly interacting dark matter based on Earth's heat flow, significantly tightening existing bounds and closing the gap between astrophysical and underground detector constraints.

Contribution

It provides a novel constraint on dark matter-nucleon cross sections for a wide mass range, based on Earth's heat flow measurements, which was previously unexplored.

Findings

Dark matter with large cross sections would produce excessive Earth's heat.

The new constraint narrows the allowed dark matter-nucleon cross section range.

Dark matter must have a truly weak interaction with nucleons within the studied mass range.

Abstract

We point out a new and largely model-independent constraint on the dark matter scattering cross section with nucleons, applying when this quantity is larger than for typical weakly interacting dark matter candidates. When the dark matter capture rate in Earth is efficient, the rate of energy deposition by dark matter self-annihilation products would grossly exceed the measured heat flow of Earth. This improves the spin-independent cross section constraints by many orders of magnitude, and closes the window between astrophysical constraints (at very large cross sections) and underground detector constraints (at small cross sections). In the applicable mass range, from about 1 to about 10^{10} GeV, the scattering cross section of dark matter with nucleons is then bounded from above by the latter constraints, and hence must be truly weak, as usually assumed.