Probing Light DM through Migdal Effect with Spherical Proportional Counter

TL;DR

This paper explores the potential of the Spherical Proportional Counter to detect light dark matter via the Migdal effect, highlighting its sensitivity to DM masses as low as 10 MeV and the influence of velocity distribution assumptions.

Contribution

It introduces the use of SPC with single-electron detection for light DM detection via the Migdal effect, considering various velocity distributions and momentum effects.

Findings

Probing DM masses down to ~10 MeV with Xenon and Neon targets.

Detection sensitivity is highly affected by the high-velocity tail of the DM distribution.

Bounds on DM-nucleus cross section vary significantly with different velocity models.

Abstract

Owing to its low electronic noise and flexible target materials, the Spherical Proportional Counter (SPC) with a single electron detection threshold can be utilized to search for sub-GeV dark matter (DM). In this work, we investigate the prospects for light DM direct detection through the DM-nucleus Migdal effect in the DARKSPHERE detector. We consider the different DM velocity distributions and momentum-transfer effects. For Xenon and Neon targets, we find that the DM mass $m_{DM}$ can be probed down to as low as $m_{DM} \sim \mathcal{O}$(10) MeV, and the derived bounds on the DM-nucleus scattering cross section $\bar{\sigma}_{n}$ are sensitive to the high-velocity tails of the DM velocity distribution, which can be altered by orders of magnitude for the different DM velocity distributions in the region $m_{DM} < 10$ MeV.