Interpretation of XENON1T excess with MeV boosted dark matter *

Abstract

Abstract The XENON1T excess of keV electron recoil events may be induced by the scattering of electrons and long-lived particles with an MeV mass and high speed. We consider a tangible model composed of two scalar MeV dark matter (DM) particles, and , to interpret the XENON1T keV excess via boosted . A small mass splitting is introduced, and the boosted can be produced using the dark annihilation process of via a resonant scalar ϕ. electron scattering is intermediated by a vector boson X. Although the constraints from Big Bang nucleosynthesis, cosmic microwave background (CMB), and low-energy experiments set the mediated electron scattering cross section to be , the MeV scale DM with a resonance enhanced dark annihilation today can still provide sufficient boosted and induce the XENON1T keV excess. The relic density of is significantly reduced by the s-wave process , which is permitted by the constraints from CMB and 21-cm absorption. A very small relic fraction of is compatible with the stringent bounds on un-boosted -electron scattering in DM direct detection, and the -electron scattering is also allowed.