Flavor hierarchies from dynamical scales

Abstract

One main obstacle for any beyond the SM (BSM) scenario solving the hierarchy problem is its potentially large contributions to electric dipole moments. An elegant way to avoid this problem is to have the light SM fermions couple to the BSM sector only through bilinears,f f . This possibility can be neatly implemented in composite Higgs models. We study the implications of dynamically generating the fermion Yukawa couplings at different scales, relating larger scales to lighter SM fermions. We show that all flavor and CP-violating constraints can be easily accommodated for a BSM scale of few TeV, without requiring any extra symmetry. Contributions to B physics are mainly mediated by the top, giving a predictive pattern of deviations in ∆F = 2 and ∆F = 1 flavor observables that could be seen in future experiments.

Gauge theories of partial compositeness: scenarios for Run-II of the LHC

“…The remaining SM fields may instead be coupled bilinearly and acquire a mass via the more standard mechanism. This hybrid solution, proposed in [12,31,32], has the extra advantage of suppressing unwanted contributions to dipole moments or flavor violating operators and could be realized at low energies via the mechanism explained in [33].…”

Anarchy with linear and bilinear interactions

“…[22] that has briefly discussed them in scenarios with flavor symmetries, and refs. [23,24]. However the UV scales and the spectrum of resonances of these models, as well as the parametric dependence of the bounds, are different from the approach that we propose JHEP10 (2017)120 here.…”

“…For the neutrinos we will follow the proposal of refs. [21] and [24,28], where neutrino masses are generated by a bilinear operator involving the Left-handed leptons only, the neutrinos being Majorana fermions. We add to eqs.…”

Probing light top partners with CP violation

“…Another appealing flavor scenario, which has been recently proposed in the literature, is based on a departure from the classical partial compositeness paradigm for the light SM fermions [64][65][66][67]. In these models only the top quark (or at most the third generation fermions) are assumed to be partially composite objects at the TeV scale, while the Yukawa…”

“…This construction leads to an effective minimal flavor violation structure and efficiently reduces all flavor-violating and CP-violating effects, most noticeably in the lepton sector [67]. The bounds on the masses of the composite states are lowered to the few TeV range, thus allowing for natural models with a small amount of fine-tuning.…”