68 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.
"Bimaximal + Democratic" type neutrino mass matrix in view of quark-lepton complementarity
We demonstrate that `Bimaximal + Democratic' type neutrino mass matrix can
accommodate the deviation of from its maximal value which
referred in the literature as `quark-lepton complementarity' along with the
other present day neutrino experimental results, namely, atmospheric, CHOOZ,
neutrinoless double beta decay () and result obtained from
WMAP experiment. We define a function in terms of solar and
atmospheric neutrino mass squared differences and solar neutrino mixing angle
(obtained from different experiments and our proposed texture). The masses and
mixing angles are expressed in terms of three parameters in our proposed
texture. The allowed region of the texture parameters is obtained through
minimization of the above function. The proposed texture crucially depends on
the value of the experimental results of experiment among
all other above mentioned experiments. If, in future,
experiments, namely, MOON, EXO, GENIUS shift the lower bound on at
the higher side by one order, the present texture will be ruled out.Comment: 4 pages, 2 figure
Evaluation of the Majorana Phases of a General Majorana Neutrino Mass Matrix: Testability of hierarchical Flavour Models
We evaluate the Majorana phases for a general complex symmetric
neutrino mass matrix on the basis of Mohapatra-Rodejohann's phase convention
using the three rephasing invariant quantities , and
proposed by Sarkar and Singh. We find them interesting as they allow us to
evaluate each Majorana phase in a model independent way even if one eigenvalue
is zero. Utilizing the solution of a general complex symmetric mass matrix for
eigenvalues and mixing angles we determine the Majorana phases for both the
hierarchies, normal and inverted, taking into account the constraints from
neutrino oscillation global fit data as well as bound on the sum of the three
light neutrino masses () and the neutrinoless double beta decay
() parameter . This methodology of finding the
Majorana phases is applied thereafter in some predictive models for both the
hierarchical cases (normal and inverted) to evaluate the corresponding Majorana
phases and it is shown that all the sub cases presented in inverted hierarchy
section can be realized in a model with texture zeros and scaling ansatz within
the framework of inverse seesaw although one of the sub case following the
normal hierarchy is yet to be established. Except the case of quasi degenerate
neutrinos, the methodology obtained in this work is able to evaluate the
corresponding Majorana phases, given any model of neutrino masses.Comment: 27 pages, 16 figures, 4 tables, to appear in NP
Consequences of minimal seesaw with complex antisymmetry of neutrinos
We propose a complex extension of permutation antisymmetry in the
neutrino Majorana matrix . The latter can be realized for the Lagrangian
by appropriate CP transformations on the neutrino fields. The resultant form of
is shown to be simply related to that with a complex (CP) extension of
permutation symmetry, with identical phenomenological consequences,
though their group theoretic origins are quite different. We investigate those
consequences in detail for the minimal seesaw induced by two strongly
hierarchical right-chiral neutrinos and with the result that the
Dirac phase is maximal while the two Majorana phases are either 0 or . We
further provide an uptodate discussion of the process
vis-a-vis ongoing and forthcoming experiments. Finally, a thorough treatment is
given of baryogenesis via leptogenesis in this scenario, primarily with the
assumption that the lepton asymmetry produced by the decays of only
matters here with the asymmetry produced by being washed out. Tight upper
and lower bounds on the mass of are obtained from the constraint of
obtaining the correct observed range of the baryon asymmetry parameter and the
role played by is elucidated thereafter. The mildly hierarchical
right-chiral neutrino case (including the quasidegenerate possibility) is
discussed in an Appendix.Comment: 30 pages, 6 figures, 4 tables, version to appear in JHE
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