From flavor puzzles to new dynamics

A particularly puzzling feature of the SM is its flavor sector. It is the least constrained theoretically, accounting for about two-third of the SM free parameters. At the same time, the measured values of the quark and lepton masses and mixings show peculiar hierarchies, and hint at some yet unknown organizing principle. Phenomenologically, in the absence of this full theory of flavor, most New Physics models have no reason to preserve the SM flavor hierarchies and the associated accidental or approximate symmetries. As a result, they end up seriously constrained by flavor observables, and their typical scale are often pushed well beyond the reach of the LHC.

In this talk, our goal will be to show that the peculiar hierarchies exhibited in the SM, instead of hindering the presence of New Physics at the TeV scale, could actually point towards specific new dynamics. We will discuss two examples. First, we will detail the possibility of TeV-scale baryon number violating processes, which in a supersymmetric context could explain the current absence of New Physics signals at the LHC. Then, we will turn to the unification of quarks and leptons. We will describe a mechanism by which the large top quark mass can render its third-generation leptonic partner very light. This state is thus identified with the electron. We will then show how to implement dynamically this mechanism, using tree-level exchanges of TeV-scale vector leptons to relate the quark and charged lepton flavor structures.

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