Lepton flavour violation from an anomaly-free leptophilic axion-like particle

TL;DR

This paper investigates a leptophilic axion-like particle motivated by Xenon1T results, exploring its potential to cause charged-lepton flavour violation and its compatibility with astrophysical constraints.

Contribution

It introduces two models of anomaly-free leptophilic ALPs and analyzes their implications for CLFV and astrophysical observations.

Findings

A keV ALP can explain Xenon1T and remain consistent with astrophysical limits.

Future CLFV experiments could test the ALP hypothesis if Xenon1T results are confirmed.

Leptophilic ALPs offer a viable link between dark matter signals and flavour physics.

Abstract

Motivated by the recent Xenon1T result, we study a leptophilic flavour-dependent anomaly-free axion-like particle (ALP) and its effects on charged-lepton flavour violation (CLFV). We present two representative models. The first one considers that the ALP origins from the flavon that generates the charged-lepton masses. The second model assumes a larger flavour symmetry such that more general mixings in the charged-lepton are possible, while maintaining flavour-dependent ALP couplings. We find that a keV ALP explaining the Xenon1T result is still viable for lepton flavour violation and stellar cooling astrophysical limits. On the other hand, if the Xenon1T result is confirmed, future CLFV measurements can be complementary to probe such a possibility.