4,615 research outputs found
Leptogenesis bound on neutrino masses in left-right symmetric models with spontaneous D-parity violation
We study the baryogenesis via leptogenesis in a class of left-right symmetric
models, in which -parity is broken spontaneously. We first discuss the
consequence of the spontaneous -parity breaking on the neutrino masses. Than
we study the lepton asymmetry in various cases, from the decay of right handed
neutrino as well as the triplet Higgs, depending on their relative masses they
acquire from the symmetry breaking pattern. The leptogenesis bound on their
masses are discussed by taking into account the low energy neutrino oscillation
data. It is shown that a TeV scale leptogenesis is viable if there are
additional sources of CP violation like domain wall originating from the
spontaneous -parity violation.Comment: 32 pages (revtex), 12 eps figures, clarifications are added in
section VII, A new section VIII is added, useful references are added.
Journal version, To appear in Phys. Rev.
Possible textures of the fermion mass matrices
Texture specific fermion mass matrices have played an important role in
understanding several features of fermion masses and mixings. In the present
work, we have given an overview of all possible cases of Fritzsch-like as well
as non Fritzsch-like texture 6 and 5 zero fermion mass matrices. Further, for
the case of texture 4 zero Fritzsch-like quark mass matrices, the issue of the
hierarchy of the elements of the mass matrices and the role of their phases
have been discussed. Furthermore, the case of texture 4 zero Fritzsch-like
lepton mass matrices has also been discussed with an emphasis on the hierarchy
of neutrino masses for both Majorana and Dirac neutrinos.Comment: 21 pages, 3 figure
Neutrino-Mass Hierarchies and Non-linear Representation of Lepton-Flavour Symmetry
Lepton-flavour symmetry in the Standard Model is broken by small masses for
charged leptons and neutrinos. Introducing neutrino masses via dimension-5
operators associated to lepton-number violation at a very high scale, the
corresponding coupling matrix may still have entries of order 1, resembling the
situation in the quark sector with large top Yukawa coupling. As we have shown
recently, in such a situation one may introduce the coupling matrices between
lepton and Higgs fields as non-linear representations of lepton-flavour
symmetry within an effective-theory framework. This allows us to separate the
effects related to the large mass difference observed in atmospheric neutrino
oscillations from those related to the solar mass difference. We discuss the
cases of normal or inverted hierarchical and almost degenerate neutrino
spectrum, give some examples to illustrate minimal lepton-flavour violation in
radiative and leptonic decays, and also provide a systematic definition of
next-to-minimal lepton-flavour violation within the non-linear framework.Comment: 17 pages, 1 figur
Supersymmetric Jarlskog Invariants: the Neutrino Sector
We generalize the notion of the Jarlskog invariant to supersymmetric models
with right--handed neutrinos. This allows us to formulate basis--independent
necessary and sufficient conditions for CP conservation in such models.Comment: 10 pages, no figure
Hierarchical neutrino masses and mixing in non minimal-SU(5)
We consider the problem of neutrino masses and mixing within the framework of
a non-minimal supersymmetric SU(5) model extended by adding a set of 1,24
chiral superfields accommodating three right-handed neutrinos. A Type I+III
see-saw mechanism can then be realized giving rise to a hierarchical mass
spectrum for the light neutrinos of the form m_3> m_2>> m_1 consistent with
present data. The extra colored states are pushed to the unification scale by
proton stability constraints, while the intermediate see-saw energy scale and
the unification scale are maintained in phenomenologically acceptable ranges.
We also examine the issue of large neutrino mixing hierarchy \theta_{23}>
\theta_{12}>> \theta_{13} in the above framework of hierarchical neutrino
masses.Comment: 12 pages, 1 figure, 1 table. Captions inserted, 2 sentences for
clarification added, 2 references adde
Unitarity violation in sequential neutrino mixing in a model of extra dimensions
We investigate the possibility of unitarity violation in the sequential
neutrino mixing matrix in a scenario with extra compact spacelike dimensions.
Gauge singlet neutrinos are assumed to propagate in one extra dimension, giving
rise to an infinite tower of states in the effective four-dimensional theory.
It is shown that this leads to small lepton-number violating entries in the
neutrino mass matrix, which can violate unitarity on the order of one per cent.Comment: 16 pages, 2 table
Neutrinoless double beta decay and neutrino mass hierarchies
In the framework of the see-saw mechanism the normal hierarchy is favorable
for the neutrino mass spectrum. For this spectrum we present a detailed
calculation of the half-lives of neutrinoless double beta decay for several
nuclei of experimental interest. The half-lives are evaluated by considering
the most comprehensive nuclear matrix elements, which were obtained within the
renormalized QRPA by the Bratislava-Caltech-Tuebingen group. The dependence of
the half-lives on sin^2 theta_{13}$ and the lightest neutrino mass is studied.
We present also the results of the calculations of the half-lives of
neutrinoless double beta decay in the case of the inverted hierarchy of
neutrino masses.Comment: 13 pages, 3 figure
Non-thermal leptogenesis with strongly hierarchical right handed neutrinos
Assuming the Dirac-type neutrino masses m_D are related to quark or charged
lepton masses, neutrino oscillation data indicate that right handed neutrino
masses are in general strongly hierarchical. In particular, if m_D is similar
to the up-type quark masses, the mass of the lightest right handed neutrino
M_1<~10^6 GeV. We show that non-thermal leptogenesis by inflaton decay can
yield sufficient baryon asymmetry despite this constraint, and discuss how the
asymmetry is correlated with the low energy neutrino masses and CP-violating
phases.Comment: 7 pages, 5 figures. v2: added some comments and references, v3: minor
corrections and additions, v4: a typo corrected, published versio
Lepton flavour violation in The Little Higgs model
Little Higgs models with T-parity have a new source of lepton flavour
violation. In this paper we consider the anomalous magnetic moment of the muon
\gmtwo and the lepton flavour violating decays \mutoeg and \tautomug in Little
Higgs model with T-parity \cite{Goyal:2006vq}. Our results shows that present
experimental constraints of \mutoeg is much more useful to constrain the new
sources of flavour violation which are present in T-parity models.Comment: LaTeX file with 13 eps figures (included
Neutrinoless double-beta decay. A brief review
In this brief review we discuss the generation of Majorana neutrino masses
through the see-saw mechanism, the theory of neutrinoless double-beta decay,
the implications of neutrino oscillation data for the effective Majorana mass,
taking into account the recent Daya Bay measurement of theta_13, and the
interpretation of the results of neutrinoless double-beta decay experiments.Comment: 22 page
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