Constraining CP-violating axion couplings

Although the Standard Model of particle physics (SM) has been very successful, it is unable to explain several observations such as neutrino masses, Dark Matter (DM), and the Baryon asymmetry of the Universe (BAU). Many models that aim to explain the BAU introduce new sources of CP violation which worsens the strong-CP problem of the SM, thereby strengthening the motivation for a solution through axions. In this talk, I will discuss a class of models which extend the SM with new sources of CP violation as well as an axion-like particle. I will show how this gives rise to CP-violating axion interactions that induce long-range forces. This scenario can be probed by electric-dipole-moments, searches for long-range axion forces, and, in case the axion-like particle makes up DM, limits on the variation of fundamental constants. I will discuss how effective-field-theory techniques allow us to describe all of these different effects in the same framework, which will require input from hadronic, nuclear, and atomic physics. I conclude by comparing the different constraints, showing that electric dipole moments are the most sensitive probes in large parts of parameter space.