274 research outputs found
Neutrino masses through see-saw mechanism in 3-3-1 models
Some years ago it was shown by Ma that in the context of the electroweak
standard model there are, at the tree level, only three ways to generate small
neutrino masses by the see-saw mechanism via one effective dimension-five
operator. Here we extend this approach to 3-3-1 chiral models showing that in
this case there are several dimension-five operators and we also consider their
tree level realization.Comment: RevTex, 7 pages and 4 .eps figures. Version published in Phys. Rev.
D. with a change in the titl
Comparison of the growth and leaf mineral concentrations between three grapevine rootstocks and their corresponding tetraploids inoculated with an arbuscular mycorrhizal fungus Gigaspora margarita
Effects of the arbuscular mycorrhizal (AM) fungus Gigaspora margarita BECKER and HALL on growth and leaf mineral concentrations of the tetraploid grapevine rootstocks Gloire de Montpellier (Gloire, Vitis riparia MICHX.), Rupestris St. George (St. George, V. rupestris SCHEELE), and Couderc 3309 (3309, V. riparia x V. rupestris) were compared with those of their corresponding diploids. The percentage of AM infection in the inoculated tetraploid grapevines of each rootstock was as high (above 90 %) as in the inoculated diploids. Shoot and root growth in the inoculated grapevines of each tetraploid was significantly higher than that in the non-inoculated grapevines. For the original diploid rootstocks, almost the same shoot and root growth was observed regardless of inoculation. Tetraploid and diploid rootstocks with AM fungi-inoculation had significantly higher P concentrations in the leaves than the non-inoculated grapevines, but tetraploid grapevines with AM fungi-inoculation had lower Ca and Mg concentrations. The tetraploid grapevines with thicker roots and more compact root systems were considered to depend more on arbuscular mycorrhizas than the original diploid rootstock cultivars.
Lepton masses in a supersymmetric 3-3-1 model
We consider the mass generation for both charginos and neutralinos in a 3-3-1
supersymmetric model. We show that R-parity breaking interactions leave the
electron and one of the neutrinos massless at the tree level. However the same
interactions induce masses for these particles at the 1-loop level. Unlike the
similar situation in the MSSM the masses of the neutralinos are related to the
masses of the charginos.Comment: RevTex, 11 pages incluing 2 .eps figures. Extended published versio
Neutrino Mass Textures with Maximal CP Violation
We have found three types of neutrino mass textures, which give maximal
CP-violation as well as maximal atmospheric neutrino mixing. These textures are
described by six real mass parameters: one specified by two complex flavor
neutrino masses and two constrained ones and the others specified by three
complex flavor neutrino masses. In each texture, we calculate mixing angles and
masses as well as Majorana CP phases.Comment: 10 pages, RevTex, no figures, references updated, version to appear
in Phys. Rev.
The Interplay between Neutrinos and Charged Leptons in the Minimal SU(3)_LxU(1)_N Gauge Model
In the minimal SU(3)_LxU(1)_N gauge model with a global L_e-L_mu-L_tau (=L')
symmetry and a discrete Z_4 symmetry, it is found that the interplay between
neutrinos and charged leptons contained in triplets of \psi^i=(\nu^i_L,
\ell^i_L, \ell^{ci}_L) (i=1,2,3) naturally leads to the large mixing angle
(LMA) MSW solution. The model includes two (anti)sextet Higgs scalars, S^(0)
with L'=0 and S^(+) with L'=2, which, respectively, couple to \psi^1\psi^{2,3}
for the electron mass and masses of atmospheric neutrinos and to
\psi^{2,3}\psi^{2,3} for the \mu- and \tau-masses and one-loop radiative
neutrino masses relevant to solar neutrinos. This mechanism is realized by
utilizing an additional residual discrete symmetry supplied by explicitly
broken L', which guarantees the absence of tree-level neutrino mass terms of
the \psi^{2,3}\psi^{2,3}-type. Pure rotation effects due to the diagonalization
of neutrino and charged-lepton mass matrices are estimated to yield \Delta
m^2_\odot/\Delta m^2_{atm} \leq (m_e/m_\mu)^{3/2}=O(10^{-4}) but the radiative
effects supersede the rotation effects to yield \Delta m^2_\odot/\Delta
m^2_{atm}=O(10^{-2}) as the LMA solution.Comment: 16 pages, RevTeX, including 2 figures with typos and misprints
corrected and with modifications in sections II-B and V, accepted by Nuclear
Physics
Two Categories of Approximately mu-tau Symmetric Neutrino Mass Textures
Our approximately \mu-\tau symmetric neutrino mass textures fall into two
different categories, whose behaviors in the \mu-\tau symmetric limit are
characterized by either \sin(theta_{13})->0 (referred to as C1)), or
\sin(theta_{12})->0 (referred to as C2)). We present ten phenomenologically
viable neutrino mass textures: two for the normal mass hierarchy, three for the
inverted mass hierarchy, and five for the quasi degenerate mass pattern. Tiny
\mu-\tau symmetry breaking ensures that \sin^2(theta_{13}) << 1 for C1), and
\Delta m^2_\odot/\Delta m^2_{atm} (\equiv R) << 1 for C2). A correlation among
small quantities is provided by \cos 2(theta_{23}) \sim \sin(theta_{13}) for
C1), and by either \cos(2theta_{23}) \sim R, or
\cos(2theta_{23})\sin(theta_{13}) \sim R for C2). It is further shown that
\tan(2theta_{12}) \sim \cos(2theta_{23})/\sin(theta_{13}) is satisfied for C2).
We find specific properties for each mass ordering, which are discussed in this
article.Comment: 31 pages, 15 figures (High-resolution figures can be downloaded from
http://www.sp.u-tokai.ac.jp/~yasue/two_categories_of.pdf.tar.gz
Quartic Gauge Boson Couplings and Tree Unitarity in the SU(3)_C X SU(3)_L X U(1)_N Models
The quartic gauge boson couplings in the models are presented. We find that the couplings of four {\it
differrent} gauge bosons may have unusual Lorentz structure and the couplings
sastify the tree unitarity requirement at high energy limit.Comment: 13 pages, Latex, axodraw.st
Can the Zee Model Explain the Observed Neutrino Data?
The eigenvalues and mixing angles in the Zee model are investigated
parameter-independently. When we require |\Delta m^2_{12}/\Delta m^2_{23}| \ll
1 in order to understand the solar and atmospheric data simultaneously, the
only solution is one which gives bi-maximal mixing. It is pointed out that the
observed values \sin^2 2\theta_{solar} \simeq 0.66 in the MSW LMA solution
cannot be explained within the framework of the Zee model, because we derive a
severe constraint on the value of \sin^2 2 \theta_{solar}, \sin^2 2
\theta_{solar} \geq 1 -(1/16)(\Delta m^2_{solar}/\Delta m^2_{atm})^2.Comment: Latex file, 10 pages, 1 figure, explanations and references added,
typos corrected, to be published in Phys.Rev.
Bilarge Neutrino Mixing and \mu - \tau Permutation Symmetry for Two-loop Radiative Mechanism
The presence of approximate electron number conservation and \mu-\tau
permutation symmetry of S_2 is shown to naturally provide bilarge neutrino
mixing. First, the bimaximal neutrino mixing together with U_{e3}=0 is
guaranteed to appear owing to S_2 and, then, the bilarge neutrino mixing
together with |U_{e3}|<<1 arises as a result of tiny violation of S_2. The
observed mass hierarchy of \Delta m^2_{\odot}<<\Delta m^2_{atm} is subject to
another tiny violation of the electron number conservation. This scenario is
realized in a specific model based on SU(3)_L x U(1)_N with two-loop radiative
mechanism for neutrino masses. The radiative effects from heavy leptons
contained in lepton triplets generate the bimaximal structure and those from
charged leptons, which break S_2, generate the bilarge structure together with
|U_{e3}|<<1. To suppress dangerous flavor-changing neutral current interactions
due to Higgs exchanges especially for quarks, this S_2 symmetry is extended to
a discrete Z_8 symmetry, which also ensures the absence of one-loop radiative
mechanism.Comment: 18 pages, 7 figures, to appear in Phys. Rev.
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