1,213 research outputs found
Scotogenic dark matter and single-zero textures of the neutrino mass matrix
The scotogenic model can simultaneously account for the presence of dark
matter and the origin of neutrino masses. We assume that the flavor neutrino
mass matrix has one zero element and Yukawa matrix elements are real in the
scotogenic model. It turns out that only one pattern of the flavor neutrino
mass matrix in the one-zero-texture scheme within the scotogenic model is
viable with the observed neutrino oscillation data, the relic abundance of the
dark matter, and the upper limit of the branching ratio of the process.Comment: 8 pages, 6 figures, references added, Accepted for publication in
Physical Review
Clockwork origin of neutrino mixings
The clockwork mechanism provides a natural way to obtain hierarchical masses
and couplings in a theory. We propose a clockwork model that has nine clockwork
generations. In this model, the candidates of the origin of the neutrino
mixings are nine Yukawa mass matrix elements that connect
neutrinos and clockwork fermions, nine clockwork mass ratios , and
nine numbers of clockwork fermions , where .
Assuming , the neutrino mixings originate from the pure
clockwork sector. We show that the observed neutrino mixings are exactly
obtained from a clockwork model in the case of the origin
scenario. In the origin scenario, the correct order of magnitude
of the observed neutrino mixings is obtained from a clockwork model.Comment: 9 pages, 4 figures. Accepted for publication in Physical Review
Comment on Neutrino Masses and Oscillations in an Model with Radiative Mechanism
We discussed how neutrino masses and oscillations are radiatively generated
in an gauge model with a symmetry based on
(). The model is characterized by lepton
triplets , where are negatively
charged heavy leptons, an triplet Higgs scalar and a singlet
Higgs scalar . These Higgs scalars can be interpreted as a Zee's and
Zee-Babu's scalar for radiative mechanisms. We demonstrated that the mass
hierarchy of arise as a consequence
of the dynamical hierarchy between -conserving one-loop effects and
-violating two-loop effects, and our model is relevant to yield
quasivacuum solution for solar neutrino problem.Comment: 6 Pages, Latex2e, RevTex macr
Two-loop Radiative Corrections to Neutrino Masses in Gauge Models
We have constructed two gauge models with the
symmetry, which accommodate tiny neutrino masses
generated by one-loop and two-loop radiative effects. The heavy neutral leptons
and heavy charged leptons are employed to specify the lepton triplets in
, respectively, accompanied by (, , ) and
(, , ), where stands for the standard Higgs scalar
and is a key ingredient for radiative mechanisms. From our numerical
calculations, we find that both our models are relevant to yield the VO
solution to the solar neutrino problem.Comment: Talk at Post Summer Institute 2000 on Neutrino Physics, August 21-24,
2000, Fuji-Yoshida, Japa
Neutrino Oscillations Induced by Two-loop Radiative Effects
Phenomena of neutrino oscillations are discussed on the basis of two-loop
radiative neutrino mechanism. Neutrino mixings are experimentally suggested to
be maximal in both atmospheric and solar neutrino oscillations. By using ()-conservation, which, however, only ensures
the maximal solar neutrino mixing, we find that two-loop radiative mechanism
dynamically generates the maximal atmospheric neutrino mixing and that the
estimate of
explains because of , where measures the breaking of the -conservation.
Together with eV, this estimate
yields eV for , which
corresponds to the LOW solution to the solar neutrino problem. Neutrino mass
scale is given by ( 1 TeV), which is of
order 0.01 eV.Comment: 10 pages,6 figures,Talk given at the Post Summer Institute 2000 on
Neutrino Physics, August 21-24, 2000, Fuji-Yoshida, Yamanashi, Japa
Fermi-Boltzmann statistics of neutrinos and relativistic effective degrees of freedom
We investigate the effect of the presence of non-pure fermionic neutrinos on
the relativistic effective degrees of freedom in the early universe. The
statistics of neutrinos is transformed continuously from Fermi-Dirac to
Maxwell-Boltzmann statistics. We find that the relativistic degrees of freedom
decreases with the deviation from pure Fermi-Dirac statistics of neutrinos if
there are constant and large lepton asymmetries. Additionally, we confirm that
the change of the statistics of neutrinos from Fermi-Dirac to Maxwell-Boltzmann
is not sufficient to cover the excess of the effective number of neutrinos.Comment: 15 pages, 5 figures, version to appear in Modern Physics Letters
Asymmetric dark matter and effective number of neutrinos
We study the effect of the MeV-scale asymmetric dark matter annihilation on
the effective number of neutrinos at the epoch of the big bang
nucleosynthesis. If the asymmetric dark matter couples more strongly to
the neutrinos than to the photons and electrons ,
, or , the lower mass limit on the asymmetric dark
matter is about MeV for .Comment: 13 pages, 14 figures, version accepted for publication in Physical
Review
Formulae for flavour neutrino masses and its application to texture two zeros
We demonstrate the usefulness of flavour neutrino masses expressed in terms
of and . The analytical expressions for the
flavour neutrino masses, mass eigenstates and physical CP-violating Majorana
phases for texture two zeros are obtained exactly.Comment: 8 pages, 2 figures, version accepted for publication in Physical
Review
Spinor Representation of for
All possible permutations in the discrete group are classified by three
rotation angles associated with the orthogonal group . We construct a
spinor representation of , which is transformed by three
44 matrices corresponding to three Pauli matrices in . An
irreducible decomposition of supplies a vector
representation of {\bf 3} of , thereby, of . Our construction is
consistent with the mathematical fact that .
The parity in the spinorial space is described by a block
off-diagonal matrix as the spinorial parity operator, whose eigenvalues are
consistent with .Comment: 11 page
Parafermionic dark mater
To discuss the possible contribution of parafermions to the dark matter
abundance, we extend the Boltzmann equation for fermionic dark matter to
include parafermions. Parafermions can accommodate particles per quantum
state , where the parafermion of order is identical to
the ordinary fermion. It is found that the parafermionic dark matter can be
more abundant than the fermionic dark matter in the present universe.Comment: 7 pages, 7 figures. Some changes in the wording. Accepted for
publication in Physical Review
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