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

Abstract

The Minimal Lepton Flavour Violation (MLFV) framework is discussed after the recent indication for CP violation in the leptonic sector. Among the three distinct versions of MLFV, the one with degenerate right-handed neutrinos will be disfavoured, if this indication is confirmed. The predictions for leptonic radiative rare decays and muon conversion in nuclei are analysed, identifying strategies to disentangle the different MLFV scenarios. The claim that the present anomalies in the semi-leptonic B-meson decays can be explained within the MLFV context is critically re-examined concluding that such an explanation is not compatible with the present bounds from purely leptonic processes.

Distinguishing a Higgs-like dilaton scenario with a complete bosonic effective field theory basis

“…However, as adopted in the context of the so-called Minimal Flavour Violation [68][69][70][71][72][73][74][75][76][77][78][79][80][81][82], or more in general in flavour models [83][84][85][86][87][88][89][90][91][92][93][94][95][96][97][98], a strategy to reestablish scale invariance consists in enlarging the spectrum by the addition of a scalar field, χ(x), that transforms under the scale symmetry: insertion of powers of this scalar field in the Lagrangian operators then allows to recover exactly scale invariance. Once it develops a VEV, fermion and scalar masses are correctly described and the scale symmetry is spontaneously broken with the arising of the corresponding GB, the dilaton.…”

The minimal flavour violating axion

“…Ref. [45] (see figure 1) shows that, for x ℓ = 0, the present data on the µ → e conversion in golden nuclei largely excludes the parameter space for this model. A straightforward computation for x ℓ = 2 and ǫ = 0.23 easily reveals that the parameter space is practically excluded.…”

“…According to the modern realisation of MFV [41][42][43][44][45], the SM fermionic kinetic terms exhibit a U(3) 5 flavour symmetry that can be decomposed into the product of an Abelian and a non-Abelian factor, G NA F × G A F where…”

Exotic vectorlike quark phenomenology in the minimal linear σ model

“…The proto-Yukawa interactions among the exotic fermions and the scalar quintuplet are written in the third line. Finally the last two lines show the SO(5) breaking interactions between the exotic and the elementary quarks: the terms ∆ 2×5 and ∆ 5×1 denote spurion fields [63][64][65][66][67] that connect the exotic and the elementary sector and are the responsible of the light fermion masses. According to the fermion partial compositeness paradigm, no direct elementary fermion couplings to φ are allowed.…”