The KSVZ Axion and Pseudo-Nambu-Goldstone Boson Models for the XENON1T Excess

Understand

The XENON1T excess can be explained by the Axion Like Particle (ALP) dark matter with mass around 2.5 keV.

• However, there are three problems needed to be solved: suppressing the coupling $g_{a\gamma}$ between the ALP and photon, and generating the proper coupling $g_{ae}$ between the ALP and electron as well as the correct ALP mass.
• We propose three models to solve these problems.
• In our models, the $g_{ae}$ couplings are produced by integrating out the vector-like leptons, and the correct ALP masses arise from high-dimensional operators.