232 research outputs found
Neutrino phenomenology and stable dark matter with A4
We present a model based on the A4 non-abelian discrete symmetry leading to a
predictive five-parameter neutrino mass matrix and providing a stable dark
matter candidate. We found an interesting correlation among the atmospheric and
the reactor angles which predicts theta_23 ~ pi/4 for very small reactor angle
and deviation from maximal atmospheric mixing for large theta_13. Only normal
neutrino mass spectrum is possible and the effective mass entering the
neutrinoless double beta decay rate is constrained to be |m_ee| > 4 10^{-4} eV.Comment: 7 pages, 2 figures, minor changes to match the version to appear in
PL
An S4 model for quarks and leptons with maximal atmospheric angle
We consider a model for quark and lepton masses and mixings based on S4
flavor symmetry. The model contains six Higgs doublets where three of them give
mass to the leptons and the other three gives mass to the quarks. Charged
fermion and quark masses arise from renormalizable interactions while neutrino
Majorana masses are generated through effective dimension five Weinberg
operator. From the study of the minimization of the scalar potential we found a
residual mu-tau symmetry in the neutrino sector predicting zero reactor angle
and maximal atmospheric angle and for the quark sector we found a four-zero
texture. We give a fit of the mass hierarchies and mixing angles in the quark
sector.Comment: some misprinting corrected, one reference and one commment added,
version to be published on Phys. Rev.
Fritzsch neutrino mass matrix from S3 symmetry
We present an extension of the Standard Model (SM) based on the discrete
flavor symmetry S3 which gives a neutrino mass matrix with two-zero texture of
Fritzsch-type and nearly diagonal charged lepton mass matrix. The model is
compatible with the normal hierarchy only and predicts the sine squared of the
reactor angle to be 0.01 at the best fit values of solar and atmospheric
parameters and maximal leptonic CP violation.Comment: 14 pages and 3 figures. Final version to appear in J. Phys
Tri-Bimaximal lepton mixing with A4 semidirect product Z2 x Z2 x Z2
We consider a model based on A4 semidirect product (Ze x Zmu x Ztau) flavor
symmetry for Tri-Bimaximal lepton mixing with two scalar A4-triplets whose
vacuum expectation values have the same alignment. Neutrino masses are
generated through effective dimension five Weinberg operators. Charged leptons
mass hierarchies are generated with an additional Froggatt-Nielsen U(1) flavor
symmetry under which right-handed leptons are charged.Comment: 7 pages, added one reference and few comments, version accepted for
PR
Modelling tri-bimaximal neutrino mixing
We model tri-bimaximal lepton mixing from first principles in a way that
avoids the problem of the vacuum alignment characteristic of such models. This
is achieved by using a softly broken A4 symmetry realized with an isotriplet
fermion, also triplet under A4. No scalar A4-triplet is introduced. This
represents one possible realization of general schemes characterized by the
minimal set of either three or five physical parameters. In the three parameter
versions mee vanishes, while in the five parameter schemes the absolute scale
of neutrino mass, although not predicted, is related to the two Majorana
phases. The model realization we discuss is potentially testable at the LHC
through the peculiar leptonic decay patterns of the fermionic and scalar
triplets.Comment: some changing, reference adde
Relating quarks and leptons without grand-unification
In combination with supersymmetry, flavor symmetry may relate quarks with
leptons, even in the absence of a grand-unification group. We propose an
SU(3)xSU(2)xU(1) model where both supersymmetry and the assumed A4 flavor
symmetries are softly broken, reproducing well the observed fermion mass
hierarchies and predicting: (i) a relation between down-type quarks and charged
lepton masses, and (ii) a correlation between the Cabibbo angle in the quark
sector, and the reactor angle characterizing CP violation in neutrino
oscillations.Comment: 4 pages, 2 figures, version published in PR
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