32 research outputs found
Constraining {\it CP} violation in a softly broken symmetric Model
To understand the mass spectra of charged lepton and neutrino symmetry
has been proposed in addition with the Standard model.
We break symmetry softly and the deviation from the tri-bimaximal mixing
arises due to Zee mechanism. In the present work, we express two mixing angles
and in terms of a single model parameter and
experimental observables, such as, mixing angle , mass squared
differences and . Using the experimental
values of , , and
we restrict the model parameter and we predict . This model gives
rise to if we allow deviation of
and deviation of from their best fit
values. Utilizing all those constraints, we explore the extent of CP violation
parameter in the present model and found a value of (for deviation of and
deviation of ) consistent with the other neutrino
experimental results. We have studied the mass pattern of neutrino and
neutrinoless double beta decay parameter
in this model.Comment: 16 pages, 6 eps figures,revised materials and figures, version to
appear in Phys.Rev.
Neutrino Yukawa textures within type-I see-saw
The arbitrariness of Yukawa couplings can be reduced by the imposition of
some flavor symmetries and/or by the realization of texture zeros. We review
neutrino Yukawa textures with zeros within the framework of the type-I seesaw
with three heavy right chiral neutrinos and in the basis where the latter and
the charged leptons are mass diagonal. An assumed non-vanishing mass of every
ultralight neutrino and the observed non-decoupling of any neutrino generation
allow a maximum of four zeros in the Yukawa coupling matrix in family
space. There are seventy two such textures. We show that the requirement of an
exact symmetry, coupled with the observational constraints, reduces
these seventy two allowed textures to only four corresponding to just two
different forms of the light neutrino mass matrix ,
resulting in an inverted/normal mass ordering. The effect of each of these on
measurable quantities can be described, apart from an overall factor of the
neutrino mass scale, in terms of two real parameters and a phase angle all of
which are within very constrained ranges. The masses and Majorana phases of
ultralight neutrinos are predicted within definite ranges with
laboratory and cosmological observational inputs. The rate for
decay, though generally below the reach of planned experiments, could approach
it in some parameteric regions. Within the same framework, we also study Yukawa
textures with a fewer number of zeros, but with exact symmetry. We
further formulate the detailed scheme of the explicit breaking of
symmetry in terms of three small parameters for allowed four zero textures. The
observed sizable mixing between the first and third generations of neutrinos is
shown to follow for a suitable choice of these symmetry breaking parameters.Comment: invited review article, to appear in a special issue on neutrinos in
the journal Advances in High Energy Physics (AHEP
Analysis of a model with a common source of CP violation
We work in a model where all CP violating phenomena have a common source. CP
is spontaneously broken at a large scale through the phase of a complex
singlet scalar. An additional singlet vector-like down-type quark
relates this high scale CP violation to low energy. We quantitatively analyze
this model in the quark sector. We obtain the numerical values of the
parameters of the Lagrangian in the quark sector for a specific ansatz of the
down-type quark mass matrix where the weak phase is generated
minimally. vertex will modify in presence of the extra vector-like
down-type quark. From the experimental lower bound of the partial decay width
we find out the lower bound of the additional down-type quark
mass. Tree level flavor changing neutral current appears in this model due to
the presence of the extra vector-like down-type quark. We give the range of
values of the mass splitting in system
using SM box, mediating tree level and mediating one loop diagrams
together for both . We find out the analytical expression for
in this model from standard box, and Higgs mediated penguin
diagrams for system, . From this we numerically
evaluate the decay width difference . We
also find out the numerical values of the CP asymmetry parameters and
for the decays and
respectively. We get the lower bound of the scale through the upper bound
of the strong CP phase.Comment: 20 pages, no figures New materials and references have been added.
Text has been modified. To be appear in J.Phys.