Axion-like Particles at the Electron-Ion Collider

The future Electron-Ion Collider (EIC) will have the capability to collide various particle beams with large luminosities in a relatively clean environment, providing access to untouched parameter space for new physics [refs?]. In this study, we look at the EIC's sensitivity to Axion-like particles (ALPs) that are created via photon fusion and promptly decay to photons. Proton-electron collisions mildly improve the parameter space reach in the 2-6 GeV ALP mass range while collisions between lead ions and electrons improve the reach by ~10² in the same region, along with mild improvement from 6-30 GeV. This large improvement is due to the coherent scattering of electrons with lead ions, which benefits from a Z² enhancement to the cross section. A brief look into the same ALP production methods at the future Muon-Ion Collider (MuIC) yields a similar improvement of ~10² to the sensitivity in the 30-300 GeV ALP mass range due to larger beam energies.