Using dipole processes to constrain the flavour of four-fermion effective interactions

Abstract

Dipole interactions encode a rich variety of phenomena, such as radiative decays and electric dipole moments in both quark and lepton sectors, which probe physics beyond the Standard Model up to very high energy scales; due to renormalization, non-dipole operators mix into dipole ones, thus possibly generating observable effects that can be investigated by those same phenomena. I consider four-fermion contact interactions for which the leading order mixing into dipoles happens at two-loops (i.e., when one-loop effects vanish) and for which this mixing can avoid small Yukawa couplings, and then explore the phenomenological consequences for flavour and $ \mathbf{CP} $ violation coming from New Physics.