In heavy-ion collisions, the highly relativistic ions act as a strong source of electromagnetic radiation, enhanced by the large proton charge number Z.
Ultra-peripheral collisions (UPC) offer a natural environment where one can observe the photon-initiated production of Beyond Standard Model (BSM) processes with QED couplings.
One such process sensitive to BSM effects is light-by-light scattering.
This process was directly observed for the first time in UPC events at the LHC by ATLAS.
In these proceedings, the recent ATLAS measurements of light-by-light scattering are presented.
These measurements are performed using the full Run-2 dataset, which results in substantially reduced uncertainties compared to the previous measurements.
The new measurements provide a precise and unique opportunity to investigate extensions of the Standard Model, such as the presence of axion-like particles.
Measurements of tau-pair production via two-photon scattering that investigate the anomalous magnetic moment of the tau lepton are also presented. This process is also potentially sensitive to BSM effects.