Anomaly-free leptophilic axionlike particle and its flavor violating tests

C Han,M L López-Ibáñez,A Melis,J M Yang,O Vives

doi:10.1103/physrevd.103.035028

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.

Highlights

The Xenon collaboration reported the observation of an excess in the electron recoiling energy around the keV scale in the Xenon1T detector [1]
Thermally produced warm dark matter (DM) is subject to important constraints from structure formation that might be in tension with the axionlike particle (ALP) masses considered here
This bound is expected to be relaxed for our ALPs with Ωa=ΩDM ≃ 0.1 [76], it is not straightforward to rescale this constraint with the DM fraction and we leave the detailed computation for a future work

Summary

Introduction

The Xenon collaboration reported the observation of an excess in the electron recoiling energy around the keV scale in the Xenon1T detector [1]. In this work we focus on the ALP framework to explain this excess. This scenario assumes the existence of an ALP as a sizeable part of the observed dark matter (DM) abundance [2], with a mass of a few keV and a relatively weak coupling to the electron. Constraints from x-ray observations forbid the existence of an anomalous coupling of the ALP to photons for ma ≳ 0.1 keV

Objectives

Results

Conclusion