The Theory Space of the Flavour Problem

by David Richard Curtin (University of Toronto)

Thursday 20 Mar 2025, 13:30 → 14:30 Europe/Zurich

4/2-037 - TH meeting room (CERN)

abstract: The masses of the SM fermions span many orders of magnitude. While technically natural, this spread and the pattern of masses and mixings beg for a deeper theoretical explanation. Many mechanisms to solve this flavour problem have been proposed, like Froggatt-Nielsen, partial compositeness, discrete symmetries etc. These mechanisms have in common that a given model realization is defined by a huge number of theory parameters, from the choice of representation to many possible coefficients or states in a given model's UV completion. This motivates a systematic approach to achieve a bird's-eye-view of a given mechanism and its potentially testable predictions at current or future experiments. In two recent papers (2306.08026, 2501.00629), we define such an approach and apply it to the Froggatt-Nielsen (FN) mechanism in the quark and lepton sector respectively. This global view of FN yields several new phenomenological insights, can be readily applied to other flavour mechanisms, and facilitates enquiries into the deeper connections between flavour and other questions like the nature of dark matter or the hierarchy problem.

davidcurtin_Froggatt-Nielsen_CERN_2025.03.20_50m_v1.pdf