Abstract
We show that the electron recoil excess around 2 keV claimed by the Xenon collaboration can be fitted by DM or DM-like particles having a fast component with velocity of order $\sim 0.1$. Those particles cannot be part of the cold DM halo of our Galaxy, so we speculate about their possible nature and origin, such as fast moving DM sub-haloes, semi-annihilations of DM and relativistic axions produced by a nearby axion star. Feasible new physics scenarios must accommodate exotic DM dynamics and unusual DM properties.
Highlights
The Xenon Collaboration reported results of searches for new physics with low-energy electronic recoil data recorded with the Xenon1T detector [1]
The excess in the electron recoil energy spectrum around 2 keV claimed by the Xenon1T Collaboration could be produced by fast dark matter (DM) or DM-like particles hitting electrons with DM velocity v ∼ 0.1
A fast DM component is needed because the cold DM with v ∼ 10−3 recoiling on electrons produces an excess at lower energies
Summary
The Xenon Collaboration reported results of searches for new physics with low-energy electronic recoil data recorded with the Xenon1T detector [1]. They claim an excess of events over the known backgrounds in the recoil energy ER range 1–7 keV, peaked around 2.4 keV. This study demonstrates the need for a flux of fast particles in order to fit the data. The Xenon1T excess needs a flux of fast (and possibly even relativistic) particles. In this work we demonstrate that a flux of fast DM can provide a good fit to the Xenon1T excess and determine the necessary flux and velocity. We later speculate about possible origins of such a fast DM component
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