Invisible decays of axion-like particles: constraints and prospects

TL;DR

This paper analyzes the constraints on axion-like particles with invisible decays, exploring their interactions with electrons and photons, and discusses future experimental prospects for detecting such particles.

Contribution

It re-evaluates existing experimental limits on ALPs with invisible decays and explores their potential to explain magnetic moment anomalies and future detection prospects.

Findings

Revised limits from collider and beam dump experiments.

Potential to explain muon and electron magnetic moment anomalies.

Future detection prospects at PADME and upgraded experiments.

Abstract

Axion-like particles (ALPs) can provide a portal to new states of a dark sector. We study the phenomenology of this portal when the ALP mainly decays invisibly, while its interaction with the standard model sector proceeds essentially via its coupling to electrons and/or photons. We re-analyse existing limits from various collider and beam dump experiments, including in particular ALP production via electron/positron interactions, in addition to the usual production through ALP-photon coupling. We further discuss the interplay between these limits and the intriguing possibility of explaining simultaneously the muon and electron magnetic moment anomalies. Finally, we illustrate the prospects of ALP searches at the LNF positron fixed-target experiment PADME, and the future reach of an upgraded experimental setup.