1,444 research outputs found
An A4 model for neutrinos
The study of an extension of the standard model based on the flavor symmetry
A4 is presented. Neutrino Majorana mass terms arise from dimension five
operator and charged lepton masses from renormalizable Yukawa couplings. We
introduce three Higgs doublets that belong to one triplet irreducible
representation of A4. We study the most general A4-invariant scalar potential
and the phenomenological consequences of the model. We find that the reactor
angle could be as large as 0.03, while the atmospheric mixing angle is close to
maximal.Comment: To appear in the proceedings of PASCOS 2010, the 16th International
Symposium on Particles, Strings and Cosmology, Valencia, Spai
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
Two-zero Majorana textures in the light of the Planck results
The recent results of the Planck experiment put a stringent constraint on the
sum of the light neutrino masses, m1+m2+m3 < 0.23 eV (95 % CL). On the other
hand, two-zero Majorana mass matrix textures predict strong correlations among
the atmospheric angle and the sum of the masses. We use the Planck result to
show that, for the normal hierarchy case, the texture with vanishing (2,2) and
(3,3) elements is ruled out at a high confidence level; in addition, we
emphasize that a future measurement of the octant of the atmospheric mixing
angle (or the one sigma determination of it based on recent fit to neutrino
data) will put severe constraint on the possible structure of the Majorana mass
matrix. The implication of the above mentioned correlations for neutrinoless
double beta-decay are also discussed, for both normal and inverted orderings.Comment: 9 pages, 8 figure
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
Neutrino masses and mixings in a Minimal S_3-invariant Extension of the Standard Model
The mass matrices of the charged leptons and neutrinos, that had been derived
in the framework of a Minimal S_3-invariant Extension of the Standard Model,
are here reparametrized in terms of their eigenvalues. The neutrino mixing
matrix, V_PMNS, is then computed and exact, explicit analytical expressions for
the neutrino mixing angles as functions of the masses of the neutrinos and
charged leptons are obtained. The reactor, theta_13, and the atmosferic,
theta_23, mixing angles are found to be functions only of the masses of the
charged leptons. The numerical values of theta_13{th} and theta_23{th} computed
from our theoretical expressions are found to be in excellent agreement with
the latest experimental determinations. The solar mixing angle, theta_12{th},
is found to be a function of both, the charged lepton and neutrino masses, as
well as of a Majorana phase phi_nu. A comparison of our theoretical expression
for the solar angle theta_12{th} with the latest experimental value
theta_12{exp} ~ 34 deg allowed us to fix the scale and origin of the neutrino
mass spectrum and obtain the mass values |m_nu1|=0.0507 eV, |m_nu2|=0.0499 eV
and |m_nu3|=0.0193 eV, in very good agreement with the observations of neutrino
oscillations, the bounds extracted from neutrinoless double beta decay and the
precision cosmological measurements of the CMB.Comment: To appear in the Proceedings of the XXIX Symposium on Nuclear
Physics, Cocoyoc, Mex., January 2006. Some typographical errors on formulae
correcte
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