Search for dark matter-nucleon interactions via Migdal effect with DarkSide-50

TL;DR

This paper reports new constraints on sub-GeV dark matter interactions using the Migdal effect in the DarkSide-50 experiment, significantly improving sensitivity to low-mass dark matter and setting the most stringent limits below 3.6 GeV/c^2.

Contribution

It introduces a novel analysis based on ionization signals alone to detect low-mass dark matter via the Migdal effect in a liquid argon detector.

Findings

Enhanced sensitivity to dark matter masses down to 40 MeV/c^2.

Most stringent upper limit on spin-independent cross section below 3.6 GeV/c^2.

New constraints improve previous bounds on low-mass dark matter interactions.

Abstract

Dark matter elastic scattering off nuclei can result in the excitation and ionization of the recoiling atom through the so-called Migdal effect. The energy deposition from the ionization electron adds to the energy deposited by the recoiling nuclear system and allows for the detection of interactions of sub-GeV/c$^2$ mass dark matter. We present new constraints for sub-GeV/c$^2$ dark matter using the dual-phase liquid argon time projection chamber of the DarkSide-50 experiment with an exposure of (12306 $\pm$ 184) kg d. The analysis is based on the ionization signal alone and significantly enhances the sensitivity of DarkSide-50, enabling sensitivity to dark matter with masses down to 40 MeV/c$^2$. Furthermore, it sets the most stringent upper limit on the spin independent dark matter nucleon cross section for masses below $3.6$ GeV/c$^2$.