Exothermic dark matter for XENON1T excess

Motivated by the recent excess in the electron recoil from XENON1T experiment, we consider the possibility of exothermic dark matter, which is composed of two states with mass splitting. The heavier state down-scatters off the electron into the lighter state, making an appropriate recoil energy required for the Xenon excess even for the standard Maxwellian velocity distribution of dark matter. Accordingly, we determine the mass difference between two component states of dark matter to the peak electron recoil energy at about 2.5 keV up to the detector resolution, accounting for the recoil events over E-R = 2 - 3 keV, which are most significant. We include the effects of the phase-space enhancement and the atomic excitation factor to calculate the required scattering cross section for the Xenon excess. We discuss the implications of dark matter interactions in the effective theory for exothermic dark matter and a massive Z ' mediator and provide microscopic models realizing the required dark matter and electron couplings to Z '.

Automated summary

In light of the excess in electron recoil observed in the XENON1T experiment, the study examines the concept of exothermic dark matter composed of two states with mass splitting. By analyzing the required recoil energy for the Xenon excess, the research determines the mass difference between the two component states and discusses the implications of dark matter interactions in the effective theory for exothermic dark matter.