Axion Dark Matter from Lepton flavor-violating Decays

TL;DR

This paper introduces models where lepton flavor-violating interactions produce axion-like dark matter via freeze-in, enhancing stability and detection prospects, and offering testable predictions for future experiments.

Contribution

It presents novel scenarios linking lepton flavor violation to axion dark matter production, improving detection sensitivity and experimental testability.

Findings

Dark matter abundance can be generated through lepton flavor-violating freeze-in.

Enhanced stability and relaxed stellar cooling constraints for axion-like particles.

Future experiments like Mu3e and MEG II can test these models.

Abstract

We propose simple scenarios where lepton flavor-violating couplings generate the observed dark matter abundance through freeze-in of an axion-like particle with mass in the few keV range. Compared to flavor-diagonal freeze-in, this mechanism enhances dark matter stability, softens stellar cooling constraints and improves the experimental sensitivity of accelerator-based searches. These scenarios can be tested by future X-ray telescopes, and in some cases will be almost entirely probed by new searches for lepton flavor violation at high-intensity experiments such as Mu3e and MEG II.