Probing light mediators at the MUonE experiment

TL;DR

The MUonE experiment can potentially detect light new physics particles, such as dark photons, $L_-_ au$ gauge bosons, and axion-like particles, by analyzing elastic muon-electron scattering with its muon beam.

Contribution

This work demonstrates MUonE's capability to explore new parameter space for light mediators beyond its primary goal of measuring muon $g-2$ contributions.

Findings

MUonE can probe sub-GeV dark photons in new parameter regions.

The experiment can explore uncharted areas of the $L_-_ au$ model.

MUonE can investigate axion-like particles with various coupling assumptions.

Abstract

The MUonE experiment, that aims to provide a precise measurement of the hadronic vacuum polarization contribution to the muon $g-2$ via elastic muon-electron scattering, has also the potential to explore the parameter space of light new physics. Exploiting the process $\mu^- N \to \mu^- N X$, where $N$ is the target nucleus and X is a new physics light mediator, we demonstrate that MUonE can be sensitive to new regions of parameter space for sub-GeV dark photons. In particular, thanks to its muon beam, MUonE will be able to explore uncharted parameter space regions for the $L_\mu-L_\tau$ model. Finally, we also find that MUonE can probe the parameter space of axion-like particles for different assumptions of the couplings to electrons, muons and photons.