Electric But Not Eclectic: Thermal Relic Dark Matter for the XENON1T Excess

Area of Science:

• Particle Physics
• Cosmology
• Astrophysics

Background:

• The nature of dark matter remains one of the most significant unsolved problems in physics.
• Experiments like XENON1T aim to directly detect dark matter particles through their interactions with ordinary matter.
• XENON1T recently observed an excess of electronic recoil events, prompting theoretical explanations.

Purpose of the Study:

• To investigate a potential dark matter model that can explain the observed excess electronic recoil events in the XENON1T experiment.
• To propose a specific particle physics model for dark matter that accounts for the XENON1T anomaly.
• To explore the implications of inelastic dark matter interactions for direct detection experiments.

Main Methods:

• Utilizing a straightforward model of inelastic dark matter produced via early Universe thermal freeze-out annihilation.
• Modeling sub-GeV mass Dirac fermion dark matter coupled to a lighter dark photon kinetically mixed with the standard model photon.
• Incorporating a scalar field to provide mass for the dark photon and split fermion state masses.

Main Results:

• The proposed inelastic dark matter model successfully accounts for the excess electronic recoil events reported by the XENON1T Collaboration.
• The model predicts dark matter particles with sub-GeV masses, interacting inelastically with electrons and nuclei.
• The model involves a dark photon and a scalar field, offering a specific particle physics framework for dark matter.

Conclusions:

• Inelastic dark matter, specifically a sub-GeV Dirac fermion coupled to a dark photon, provides a compelling explanation for the XENON1T excess.
• This model highlights the importance of considering inelastic interactions in dark matter searches.
• The findings suggest new avenues for exploring dark matter properties through direct detection experiments.