78 research outputs found
Effects of an intermediate scale in SUSY grand unification
We discuss the production of lepton flavor violation and EDMs and the
viability of the unification hypothesis in SUSY grand unification with
an intermediate gauge symmetry breaking scale.Comment: 3 pages (Latex, esprc2.sty used), talk given at 4th International
Conference on Supersymmetry (SUSY '96, College Park, MD, May 29 - June 1,
1996
Electric dipole moments and b- unification in the presence of an intermediate scale in SUSY grand unification
We show that an intermediate gauge symmetry breaking scale can be a
significant source of electric dipole moments for the electron and neutron in
supersymmetric grand unified theories. New phases, similar to that of the CKM
matrix, appear which do not arise from the supersymmetry (SUSY) breaking
operators. To illustrate, we choose some grand unified SUSY models having an
intermediate gauge symmetry breaking scale with some attractive features. We
also show how well the unification hypothesis works in this class of
models.Comment: 14 pages(Latex), 2 PS Figures (uuencoded, epsf.tex
Large neutrino mixing and normal mass hierarchy: a discrete understanding
We discuss the possibility of flavor symmetries to explain the pattern of
charged lepton and neutrino masses and mixing angles. We emphasize what are the
obstacles for the generation of an almost maximal atmospheric mixing and what
are the minimal ingredients to obtain it. A model based on the discrete
symmetry is constructed, which leads to the dominant -block in
the neutrino mass matrix, thus predicting normal hierarchy. This symmetry makes
it possible to reproduce current data and predicts
and strongly suppressed neutrinoless
-decay. Moreover, it implies a relation between lepton and quark mixing
angles: . The Cabibbo mixing can
also be reproduced and . is
thus a candidate to describe all the basic features of Standard Model fermion
masses and mixing.Comment: 9 pages, revtex, 1 eps figure; clarifications and comments added in
sections III.A.1. and III.C.; typos corrected; several references adde
Are deviation from bi-maximal mixing and none-zero U_{e3} related to non-degeneracy of heavy Majorana neutrinos?
We propose a scenario that the mass splitting between the first generation of
the heavy Majorana neutrino and the other two generations of degenerate heavy
neutrinos in the seesaw framework is responsible for the deviation of the solar
mixing angle from the maximal mixing, while keeping the maximal mixing between
the tau and muon neutrinos as it is. On top of the scenario, we show that the
tiny breaking of the degeneracy of the two heavy Majorana neutrinos leads to
the non-zero small mixing angle in the PMNS matrix and the little
deviation of the atmospheric neutrino mixing angle from the maximal mixing.Comment: 12 pages, model claified, references added and correcte
Tri-Bimaximal Neutrino Mixing from Discrete Symmetry in Extra Dimensions
We discuss a particularly symmetric model of neutrino mixings where, with
good accuracy, the atmospheric mixing angle theta_{23} is maximal, theta_{13}=0
and the solar angle satisfies sin^2(theta_{12})=1/3 (Harrison-Perkins-Scott
(HPS) matrix). The discrete symmetry A_4 is a suitable symmetry group for the
realization of this type of model. We construct a model where the HPS matrix is
exactly obtained in a first approximation without imposing ad hoc relations
among parameters. The crucial issue of the required VEV alignment in the scalar
sector is discussed and we present a natural solution of this problem based on
a formulation with extra dimensions. We study the corrections from higher
dimensionality operators allowed by the symmetries of the model and discuss the
conditions on the cut-off scales and the VEVs in order for these corrections to
be completely under control. Finally, the observed hierarchy of charged lepton
masses is obtained by assuming a larger flavour symmetry. We also show that,
under general conditions, a maximal theta_{23} can never arise from an exact
flavour symmetry.Comment: 24 pages, 1 figure, misprints corrected and references adde
Phenomenology of Pseudo Dirac Neutrinos
We formulate general conditions on neutrino mass matrices under
which a degenerate pair of neutrinos at a high scale would split at low scale
by radiative corrections involving only the standard model fields. This
generalizes the original observations of Wolfenstein on pseudo Dirac neutrinos
to three generations. A specific model involving partially broken discrete
symmetry and solving the solar and atmospheric anomalies is proposed. The
symmetry pattern of the model naturally generates two large angles one of which
can account for the large angle MSW solution to the solar neutrino problem.Comment: 15 pages LATE
Stability of Neutrino Mass Degeneracy
Two neutrinos of Majorana masses with mixing angle are
unstable against radiative corrections in the limit , but are stable
for (i.e. opposite CP eigenstates) with which
corresponds to an additional symmetry.Comment: 7 pages, no figure, one reference adde
Cancellations in Neutrinoless Double Beta Decay and the Neutrino Mass Matrix
In a degenerate scheme with mass m_0 a complete analysis of the allowed range
of the effective electron neutrino Majorana mass is performed. Special
attention is paid to effects of cancellations caused either by intrinsic CP
parities of the eigenstates (CP invariance) or by complex mixing matrix
elements (CP violation). We investigate all possibilities and give in each case
constraints on the phases, the relative CP parities or the neutrino mass scale.
A solar mixing angle \sin^2 2 \theta smaller than 0.7 jeopardizes the
degenerate mass scheme. A key value of /m_0 is identified, which is
independent on the solar solution and would rule out certain schemes. Also it
would answer the question regarding the presence of CP violation. Even if a
total neutrino mass scale and an effective mass is measured, the value of the
phases or parities is not fixed, unless in some special cases. The resulting
uncertainty in the other mass matrix elements is at least of the same order
than the one stemming from nuclear matrix elements calculations.Comment: 20 pages, 10 figures. Title, abstract and parts of the text change
Neutrino mixing schemes and neutrinoless double beta decay
We study the possible structure of the neutrino mass matrix taking into
consideration the solar and atmospheric neutrinos and the neutrinoless double
beta decay. We emphasize on mass matrices with vanishing elements. There are
only a very few possibilities remaining at present. We concentrate on three
generation scenarios and find that with three parameters there are few
possibilities with and without any vanishing elements. For completeness we also
present a five parameter four neutrino (with one sterile neutrino) mass matrix
which can explain all these experiments and the LSND result.Comment: 12 pages late
Unitarity boomerangs of quark and lepton mixing matrices
The most popular way to present mixing matrices of quarks (CKM) and leptons
(PMNS) is the parametrization with three mixing angles and one CP-violating
phase. There are two major options in this kind of parametrizations, one is the
original Kobayashi-Maskawa (KM) matrix, and the other is the Chau-Keung (CK)
matrix. In a new proposal by Frampton and He, a unitarity boomerang is
introduced to combine two unitarity triangles, and this new presentation
displays all four independent parameters of the KM parametrization in the quark
sector simultaneously. In this paper, we study the relations between KM and CK
parametrizations, and also consider the quark-lepton complementarity (QLC) in
the KM parametrization. The unitarity boomerang is discussed in the situation
of the CK parametrization for comparison with that in the KM parametrization in
the quark sector. Then we extend the idea of unitarity boomerang to the lepton
sector, and check the corresponding unitarity boomerangs in the two cases of
parametrizations.Comment: 18 latex pages, 4 figures. Version accepted for publication in PL
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