Generalised geometrical CP violation in a T ′ lepton flavour model

Abstract

Abstract:We analyse the interplay of generalised CP transformations and the nonAbelian discrete group T and use the semi-direct product G f = T H CP , as family symmetry acting in the lepton sector. The family symmetry is shown to be spontaneously broken in a geometrical manner. In the resulting flavour model, naturally small Majorana neutrino masses for the light active neutrinos are obtained through the type I see-saw mechanism. The known masses of the charged leptons, lepton mixing angles and the two neutrino mass squared differences are reproduced by the model with a good accuracy. The model allows for two neutrino mass spectra with normal ordering (NO) and one with inverted ordering (IO). For each of the three spectra the absolute scale of neutrino masses is predicted with relatively small uncertainty. The value of the Dirac CP violation (CPV) phase δ in the lepton mixing matrix is predicted to be δ ∼ = π/2 or 3π/2. Thus, the CP violating effects in neutrino oscillations are predicted to be maximal (given the values of the neutrino mixing angles) and experimentally observable. We present also predictions for the sum of the neutrino masses, for the Majorana CPV phases and for the effective Majorana mass in neutrinoless double beta decay. The predictions of the model can be tested in a variety of ongoing and future planned neutrino experiments.

Light sterile neutrinos

“…The existence of massive neutrinos at the eV scale can be probed in β-decay experiments [219][220][221][222][223][224][225] and in neutrinoless double-β decay experiments [13,106,176,[226][227][228][229][230][231][232][233][234].…”

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

“…In the field of discrete flavour models, this indication translated into looking, for the first time, for approaches and/or contexts where, besides the mixing angles, also the lepton phase(s) were predicted: new models were presented with the CP symmetry as part of the full flavour symmetry [94][95][96][97][98][99][100]; studies on the mixing patterns and their modifications to provide realistic descriptions of oscillation data were performed [101][102][103][104]; an intense activity was dedicated to investigate sum rules involving neutrino masses, mixing angles and δ CP [102][103][104][105][106][107][108][109].…”

Deviation from bimaximal mixing and leptonic CP phases in S4 family symmetry and generalized CP

“…The invariance of the light neutrino mass matrix under µ − τ reflection in the charged lepton diagonal basis leads to maximal atmospheric mixing angle θ 23 and maximal Dirac CP phase δ CP with δ CP = ±π/2 [33][34][35][36][37][38][39]. The phenomenological implications of the generalized CP symmetry has been analyzed within the context of popular A 4 [40], S 4 [30,[41][42][43][44] and T [45] family symmetries. By breaking the full symmetry down to Z 2 ×CP in the neutrino sector, the TM 1 and TM 2 mixing patterns in which the first and the second columns of the tri-bimaximal mixing is kept respectively, can be exactly produced.…”