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

Abstract

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 6.8×104 cts kg-1 yr-1 keV above 4 MeV and find no statistically significant excess over our background projection. Using a total Xe136 exposure of 234.1 kg yr, we exclude new parameter space for the charged-current absorption cross section for dark matter masses between mχ=2.6-11.6 MeV with a minimum of 6×1051 cm2 at 8.3 MeV at the 90% confidence level.