# LHC as an Axion Factory: Probing an Axion Explanation for $(g-2)_\mu$ with Exotic Higgs Decays

## TL;DR

This paper proposes that the LHC can explore a significant parameter space of axion-like particles (ALPs) that could explain the muon g-2 anomaly through exotic Higgs decays, even with suppressed couplings.

## Contribution

It demonstrates that Higgs decays to ALPs at the LHC can probe the parameter space relevant for the muon g-2 anomaly, including loop-suppressed couplings.

## Key findings

- LHC searches for $h o Za$ and $h o aa$ can test most of the ALP parameter space for muon g-2.
- Exotic Higgs decays can effectively probe ALPs with couplings as low as 0.01 TeV$^{-1}$.
- The method remains sensitive even if ALPs predominantly decay into photons with branching ratios below 1.

## Abstract

We argue that a large region of so far unconstrained parameter space for axion-like particles (ALPs), where their couplings to the Standard Model are of order $(0.01\!-\!1)\,\mbox{TeV}^{-1}$, can be explored by searches for the exotic Higgs decays $h\to Za$ and $h\to aa$ in Run-2 of the LHC. Almost the complete region in which ALPs can explain the anomalous magnetic moment of the muon can be probed by searches for these decays with subsequent decay $a\to\gamma\gamma$, even if the relevant couplings are loop suppressed and the $a\to\gamma\gamma$ branching ratio is less than~1.