LHC as an Axion Factory: Probing an Axion Explanation for $(g-2)_μ$ with Exotic Higgs Decays

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 $a\toγγ$, even if the relevant couplings are loop suppressed and the $a\toγγ$ branching ratio is less than~1.