Exploring the Dark Axion Portal in the LUXE Optical Dump Experiment

The optical dump at the Laser Und X-Ray Free-Electron Laser Experiment (LUXE) has potential to create a large flux of O(GeV) photons that can be used to look for new physics when directed at a physical dump. An extension of the experiment called LUXE-NPOD, which focuses the hard photons from LUXE onto a slab of tungsten, offers two interaction points (laser-electron and photon-tungsten), making it well-suited to probe theories containing two or more new particles. We examine the dark axion portal, a scenario involving both dark photons and axions (or axion-like particles) with a direct coupling between them, and its implications on the observed signals at LUXE-NPOD. We derive the sensitivity of this experiment to the various parameters of the theory. Our discussion strives to be systematic and demonstrates a practical method of analyzing a multi-dimensional parameter space.