Leptonic dynamical Yukawa couplings

Abstract

A dynamical origin of the Yukawa couplings is a promising scenario to explain the flavour puzzle. The focus of this letter is set on the role of the neutrino Majorana character: when an O(2) N flavour symmetry acts on the right-handed neutrino sector, the minimum of the scalar potential allows for large mixing angles -in contrast to the simplest quark case-and predicts a maximal Majorana phase. This leads to a strong correlation between neutrino mass hierarchy and mixing pattern. Realistic solutions point to the existence of three heavy right-handed neutrinos.

Revisiting Minimal Lepton Flavour Violation in the light of leptonic CP violation

“…The M(L)FV is not a complete model, as fermion masses and mixings are just described while their origin is not explained (attempts to improve with this respect can be found in refs. [66][67][68][69][70][71][72][73][74][75]). It is instead a framework where observed flavour violating observables are described in agreement with data and unobserved flavour violating signals are not expected to be observed with the current experimental sensitivities, but could be observable in the future planned experiments with significantly higher sensitivity, assuming the New Physics (NP) responsible for these phenomenology at the TeV scale or slightly higher [61][62][63][64][65][76][77][78][79][80][81][82][83][84][85][86][87][88][89].…”

“…In refs. [72][73][74] attempts have been presented to provide a dynamical explanation for the flavour puzzle in the lepton sector: as for the quark sector, the results are not conclusive, but highlighted interesting features. Indeed, for the MLFV version with an SO(3) N R symmetry factor associated to the RH neutrinos, the minima of the scalar potential, constructed by promoting Y e and Y ν to be dynamical fields, allow a maximal mixing and a relative maximal Majorana CP phase between two almost degenerate neutrino mass eigenvalues.…”

The minimal flavour violating axion

“…[64][65][66][67] (see also refs. [68][69][70][71][72]): the Yukawa spurions have been promoted to dynamical scalar fields and the corresponding scalar potential has been investigated.…”

“…[64][65][66][67] showed how the non-Abelian symmetry G N A F deals exclusively with the explanation of the inter-generation hierarchies, but cannot fix the overall coefficients c i . On the other side, the hierarchies m b /m t and m τ /m t , that correspond to c b /c t and c τ /c t in the previous expressions, can be elegantly explainà la FN mechanism: one of the Abelian factors of the whole flavour symmetry can be taken as a true symmetry of the Lagrangian; charges can be chosen such that the only terms invariant under this Abelian factor are the ones of the up-type quarks, while those describing down-type quarks and charged leptons are initially forbidden.…”

Leptogenesis andCPviolation inSU(5)models with lepton flavor mixing originating from the right-handed sector

“…The structure of the Dirac sector is motivated by an SU (5) Grand Unified Theory (GUT) embedding, which accounts not only for leptonic mixing but also for observables of the quark sector. Related works exist, where the Majorana mass terms of the neutrino sector account for the large leptonic mixing angles, e.g., [7,8] The paper is organized as follows: We start by describing the outline of the model in Sec. II proposing a possible realization in an SU (5) GUT.…”