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 axionlike particles (ALPs), where their couplings to the standard model are of order $(0.01--1)\text{ }\text{ }{\mathrm{TeV}}^{\ensuremath{-}1}$, can be explored by searches for the exotic Higgs decays $h\ensuremath{\rightarrow}Za$ and $h\ensuremath{\rightarrow}aa$ 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 $a\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$, even if the relevant couplings are loop suppressed and the $a\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ branching ratio is less than 1.