New Limits on Axionlike Particle Coupling with the Photons from Two-Photon Decays and Inverse Primakoff Scattering

Axionlike Particles (ALPs) can be produced in the Sun and is a viable candidate to the Cosmological Dark Matter. It can decay to two photons or interact with matter via Inverse Primakoff (IP) scattering. We identify inelastic channels to the IP-processes due to atomic excitation and ionization. Their cross sections are derived with full electromagnetic fields of atomic charge and current densities, and computed by well-benchmarked atomic many-body methods. Limits on ALP couplings with the photons are derived. New parameter space of ALP masses between 1~eV to 1~MeV not accessible to previous laboratory experiments is probed and excluded. The sensitivity reach in future experimental projects is projected.
1 table, 4 figures