Revisiting the fermionic dark matter absorption on electron target

Abstract

We perform a systematic study of the fermionic DM absorption interactions on electron target in the context of effective field theory. The fermionic DM absorption is not just sensitive to sub-MeV DM with efficient energy release, but also gives a unique signature with clear peak in the electron recoil spectrum whose shape is largely determined by the atomic effects. Fitting with the Xenon1T and PandaX-II data prefers DM mass at mχ = 59 keV and 105 keV, respectively, while the cut-off scale is probed up to around 1 TeV. The DM overproduction in the early Universe, the invisible decay effect on the cosmological evolution, and the visible decay signal collected by the astrophysical X(gamma)-ray observations (Insight-HXMT, NuSTAR, HEAO-1, and INTEGRAL) are thoroughly explored to constrain the DM absorption interactions. With stringent bounds on the tensor and pseudo-scalar operators, the other fermionic DM operators are of particular interest at tonne-scale direct detection experiments such as PandaX-4T, XENONnT, and LZ.