Searching for axionlike particles with data scouting at ATLAS and CMS

We investigate the physics case for a dedicated trigger-level analysis for very low mass diphoton resonances at ATLAS and CMS and introduce a new photon isolation criterion. This greatly increases the acceptance for light particles at the expense of a somewhat larger Standard Model background. We show how such an analysis would likely yield new experimental coverage for axionlike particles for masses below 15 GeV, bridging the gap with the region covered by flavor factories.