Flavour in supersymmetry: horizontal symmetries or wave function renormalisation

Abstract

Abstract:We compare theoretical and experimental predictions of two main classes of models addressing fermion mass hierarchies and flavour changing neutral currents (FCNC) effects in supersymmetry: Froggatt-Nielsen (FN) U(1) gauged flavour models and NelsonStrassler/extra dimensional models with hierarchical wave functions for the families. We show that whereas the two lead to identical predictions in the fermion mass matrices, the second class generates a stronger suppression of FCNC effects. We prove that, whereas at first sight the FN setup is more constrained due to anomaly cancelation conditions, imposing unification of gauge couplings in the second setup generates conditions which precisely match the mixed anomaly constraints in the FN setup. Finally, we provide an economical extra dimensional realisation of the hierarchical wave functions scenario in which the leptonic FCNC can be efficiently suppressed due to the strong coupling (CFT) origin of the electron mass.

Gauge mediation beyond minimal flavor violation

“…This higher suppression is reminiscent of what happens in the case of wave function renormalization [35,36] where the LL and RR MIs depend on the sum of charges instead of their difference in contrast to U(1) models. In the PC case, we have a further suppression of order (ǫ We now analyze the phenomenological implications of the flavor structure of sfermion masses in low-energy processes.…”

“…Despite the underlying U(1) flavor symmetry, the GMSB setup leads to a strong suppression for the soft terms that rather resembles the PC structure. Here the extra suppression originates in the loop origin of soft terms, which acts precisely as a wavefunction suppression [35,36]. Indeed LL and RR mass insertions are suppressed as in PC, while (effective) LR mass insertions in the up sector have roughly the same suppression.…”

“…suppression is reminiscent of what happens in the case of wave function renormalization [35,36] or Partial Compositeness [31,34], despite the underlying flavor model can be a simple U(1) flavor model (which in the context of Gravity Mediation typically suffers from strong ∆S = 2 constraints [30,70]). In FGM this extra suppression originates in the loop origin of soft terms, which acts precisely as a wavefunction suppression.…”

“…Despite the underlying U(1) flavor symmetry, the GMSB setup leads to a strong suppression for LL and RR mass insertions, which is reminiscent of what happens in the case of wave function renormalization [35,36] or Partial Compositeness [31,34]. In FGM models, the extra suppression originates in the loop origin of soft terms, which acts precisely as a wave function suppression.…”

“…loop origin of soft terms, which acts precisely as a wave function suppression [35,36]. In contrast to SUSY PC models this scenario provides complete control of the theory, and therefore allows to study the consequences of perturbative solutions to the flavor problem like e.g.…”