4 research outputs found
Repressing Anarchy in Neutrino Mass Textures
The recent results that is relatively large, of the order of
the previous upper bound, and the indications of a sizable deviation of
from the maximal value are in agreement with the predictions of
Anarchy in the lepton sector. The quark and charged lepton hierarchies can then
be reproduced in a SU(5) GUT context by attributing non-vanishing
charges, different for each family, only to the SU(5) tenplet states. The fact
that the observed mass hierarchies are stronger for up quarks than for down
quarks and charged leptons supports this idea. As discussed in the past, in the
flexible context of , different patterns of charges can
be adopted going from Anarchy to various types of hierarchy. We revisit this
approach by also considering new models and we compare all versions to the
present data. As a result we confirm that, by relaxing the extreme ansatz of
equal charges for all SU(5) pentaplets and singlets, better
agreement with the data than for Anarchy is obtained without increasing the
model complexity. We also present the distributions obtained in the different
models for the Dirac CP-violating phase. Finally we discuss the relative merits
of these simple models.Comment: v1: 12 pages, 3 figures; v2: 13 pages, 3 figures, text improved,
matches version accepted for publication; v3: submitted to add an
acknowledgment to a networ
Discrete Flavour Groups, \theta_13 and Lepton Flavour Violation
Discrete flavour groups have been studied in connection with special patterns
of neutrino mixing suggested by the data, such as Tri-Bimaximal mixing (groups
A4, S4...) or Bi-Maximal mixing (group S4...) etc. We review the predictions
for sin(\theta_13) in a number of these models and confront them with the
experimental measurements. We compare the performances of the different classes
of models in this respect. We then consider, in a supersymmetric framework, the
important implications of these flavour symmetries on lepton flavour violating
processes, like \mu -> e gamma and similar processes. We discuss how the
existing limits constrain these models, once their parameters are adjusted so
as to optimize the agreement with the measured values of the mixing angles. In
the simplified CMSSM context, adopted here just for indicative purposes, the
small tan(beta) range and heavy SUSY mass scales are favoured by lepton flavour
violating processes, which makes it even more difficult to reproduce the
reported muon g-2 discrepancy.Comment: 45 pages, 16 figures, 3 tables; V3 submitted to add an acknowledgment
to a Networ
Generalised geometrical CP violation in a T' lepton flavour model
We analyse the interplay of generalised CP transformations and the non-Abelian discrete group T \u2032 and use the semi-direct product G f = T \u2032 caH 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 \u3b4 in the lepton mixing matrix is predicted to be \u3b4 = \u3c0/2 or 3\u3c0/2. 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