Improved constraints for axion-like particles from 3-photon events at $e^+e^-$ colliders

TL;DR

This paper improves constraints on axion-like particles by analyzing 3-photon events at $e^+e^-$ colliders, especially Belle II, considering ALP couplings to photons and electrons, thus extending the search range.

Contribution

It provides detailed calculations for ALP constraints from 3-photon events at colliders, including the coupling to electrons, which was not thoroughly analyzed before.

Findings

Enhanced limits on ALP mass and couplings from collider data.

Inclusion of ALP-electron coupling extends the search parameter space.

Future collider analyses can significantly tighten ALP constraints.

Abstract

Axions and axion-like particles (ALPs) are one of the most widely discussed extensions of the Standard Model when it comes to the strong CP problem and dark matter candidates. Current experiments are focused on the indirect searches of invisible pseudoscalars in a wide parameter range. In this paper we investigate limits on ALP mass, and its couplings to photons and leptons from 3-photon annihilation at $e^+e^-$ colliders. We provide detailed calculations and apply them to the particular kinematics of the Belle II experiment, covering the ALP mass range from few hundred MeV to around 10 GeV. Our results, which improve upon previous analyses by also including the ALP coupling to electrons, show that such future analyses will allow to significantly extend the ALP search range and impose much more stringent restrictions on their couplings.