656 research outputs found
New model for the neutrino mass matrix
I suggest a model based on a softly broken symmetry L_e - L_mu - L_tau and on
Babu's mechanism for two-loops radiative generation of the neutrino masses. The
model predicts that one of the physical neutrinos (nu_3) is massless and that
its component along the nu_e direction (U_e3) is zero. Moreover, if the
soft-breaking term is assumed to be very small, then the vacuum oscillations of
nu_e have almost maximal amplitude and solve the solar-neutrino problem. New
scalars are predicted in the 10 TeV energy range, and a breakdown of e-mu-tau
universality should not be far from existing experimental bounds.Comment: 7 pages including 3 figure
A simple connection between neutrino oscillation and leptogenesis
The usual see-saw formula is modified by the presence of two Higgs triplets
in left-right symmetric theories. The contribution from the left-handed Higgs
triplet to the see-saw formula can dominate over the conventional one when the
neutrino Dirac mass matrix is identified with the charged lepton or down quark
mass matrix. In this case an analytic calculation of the lepton asymmetry,
generated by the decay of the lightest right-handed Majorana neutrino, is
possible. For typical parameters, the out-of-equilibrium condition for the
decay is automatically fulfilled. The baryon asymmetry has the correct order of
magnitude, as long as the lightest mass eigenstate is not much lighter then
10^{-6} to 10^{-8} eV, depending on the solution of the solar neutrino problem.
A sizable signal in neutrinoless double beta decay can be expected, as long as
the smallest mass eigenstate is not much lighter than 10^{-3} eV and the Dirac
mass matrix is identified with the charged lepton mass matrix.Comment: 16 pages, 3 figures. One paragraph and some references added, typos
correcte
Bilarge neutrino mixing in R-parity violating supersymmetry: the role of right-chiral neutrino superfields
We consider the possibility of neutrino mass generation in a supersymmetric
model where lepton number can be violated by odd units. The different patterns
of mixing in the quark and lepton sectors are attributed to the persence of
right-chiral neutrino superfields which (a) enter into Yukawa couplings via
non-renormalizable interaction with hidden sector fields, and (b) can violate
lepton number by odd units. Both of these features are shown to be the result
of some global quantum number which is violated when SUSY is broken in the
hidden sector. It is shown how such a scenario, together with all known
R-parity violating effects, can lead to neutrino masses and bilarge mixing via
seesaw as well as radiative mechanisms. Some sample values of the various
parameters involved, consistent with electroweak symmetry breaking constraints,
are presented as illustrations.Comment: 19 pages. Minor modificaitons are made in the text. This version is
to appear in Physical Review
Neutrino Mass Squared Differences in the Exact Solution of a 3-3-1 Gauge Model without Exotic Electric Charges
The mass splittings for the Majorana neutrinos in the exact solution of a
particular 3-3-1 gauge model are computed here in detail. Since both
and the mass splittings ratio
are taken into account, the analytical calculations
seem to predict an inverted mass hierarchy and a mixing matrix with a texture
based on a very close approximation to the bi-maximal mixing. The resulting
formulas for the mass squared differences can naturally accomodate the
available data if the unique free parameter () gets very small values
(). Consequently, the smallness of the parameter requires
(according to our method) a large breaking scale TeV
in the model. Hence, the results concerning the neutrino mass splittings may
lead to a more precise tuning in the exact solution of the 3-3-1 model of
interest, being able - at the same time - to recover all the Standard Model
phenomenology and predict the mass spectrum of the new gauge bosons
in accordance with the actual data. The minimal absolute mass
in the neutrino sector is also obtained - eV - in the case
of our suitable approximation for the bi-maxcimal mixing.Comment: 10 pages, no figure
The exact eigenstates of the neutrino mass matrix without CP-phase violation
In this paper we obtain the exact mass-eigenstates of the Majorana physical
neutrinos. We start by taking into account a general mass matrix
without any CP-phase violation. It is then diagonalized by exactly solving an
appropriate set of equations. The solution supplies straightforwardly the mass
eigenvalues depending on the diagonal entries and mixing angles. Finally, the
consequences of these analytical expressions are discussed assuming various
phenomenological restrictions such as conserving the global lepton number
and the interchange symmetry. The minimal
absolute mass in the neutrino sector is also obtained since the two plausible
scenarios invoked above are employed.Comment: 9 pages, no figure
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