Electronic and nuclear contributions in sub-GeV dark matter scattering: A case study with hydrogen

TL;DR

This paper investigates how sub-GeV dark matter interacts with hydrogen atoms, highlighting the dominance of electron interactions near thresholds and nuclear interactions at higher energies, with implications for detector design.

Contribution

It develops a general nonrelativistic effective field theory framework to compare electronic and nuclear contributions in dark matter scattering, providing insights into their relative importance.

Findings

DM-electron interactions dominate near threshold regions.

DM-nucleon interactions become more significant at higher energies.

The results help disentangle electronic and nuclear signals in detectors.

Abstract

Scattering of sub-GeV dark matter (DM) particles with hydrogen atoms is studied in this paper. The interactions of DM with electrons and nucleons are both included and formulated in a general framework based on nonrelativistic effective field theory. On the assumption of same dark matter coupling strengths, it is found that DM-electron interactions dominate the inelastic atomic transitions to discrete excited states and ionization continuum around the threshold regions, and DM-nucleon interactions become more important with increasing energy and dominate in elastic scattering. The conclusion should apply, qualitatively, to practical detector species so that electronic and nuclear contributions in DM scattering processes can be disentangled, while issues including binding effects and recoil mechanism in many-body systems will require further detailed calculations.