Search for MeV electron recoils from dark matter in EXO-200

We present a search for electron-recoil signatures from the charged-current absorption of fermionic dark matter using the EXO-200 detector. We report an average electron-recoil background rate of 6.8 × 10⁻⁴ cts kg⁻¹ yr⁻¹ keV⁻¹ above 4 MeV and find no statistically significant excess over our background projection. Using a total ¹³⁶Xe exposure of 234.1 kg yr, we exclude new parameter space for the charged-current absorption cross section for dark matter masses between 2.6 MeV and 11.6 MeV with a minimum of 6 × 10⁻⁵¹ cm² at 8.3 MeV at the 90% confidence level.

Physical Review D, 107, 012007 (2023)