Searching for axions with kaon decay at rest

We describe a novel search strategy for axions (or hadronically coupled axionlike particles) in the mass range of ma350 MeV. The search relies on kaon decay at rest, which produces a monoenergetic signal in a large volume detector (e.g., a tank of liquid scintillator) from axion decays a→γγ or a→e+e-. The decay modes K+→π+a and a→γγ are induced by the axion's coupling to gluons, which is generic to any model which addresses the strong CP problem. We recast a recent search from MicroBooNE for e+e- pairs and study prospects at JSNS2 and other near-term facilities. We find that JSNS2 will have world-leading sensitivity to hadronically coupled axions in the mass range of 40 MeVma350 MeV.