114 research outputs found
Examining the Geometrical Model with Inverted Mass Hierarchy for Neutrinos
The comprehensive analyses are presented in the model with the inverted mass
hierarchy for neutrinos, which follows from a geometrical structure of a (1+5)
dimensional space-time where two extra dimensions are compactified on the
T^2/Z_3 orbifold. The model gives two large lepton flavor mixings due to the S3
structure in the (1+5) dimensional space-time. It also predicts the lightest
neutrino mass as m_3=(1-50)\times 10^{-5}eV and the effective neutrino mass
responsible for neutrinoless double beta decays as _{ee}\simeq 50 meV. The
low energy CP violation, J_{CP} could be 0.02. On the other hand, the observed
baryon asymmetry in the present universe is produced by the non-thermal
leptogenesis, which works even at the reheating temperature
TR=10^{4}-10^{6}GeV. The correlation between the baryon asymmetry and the low
energy CP violation is examined in this model.Comment: 17 pages, 10 figures, a reference is added, minor change in
introductio
Experimental Study on Reduction of the Horizontal Subgrade Reaction due to Liquefaction
It is important to evaluate resistance strength of foundation and the subgrade reaction of soil surrounding the foundation during an earthquake when a bridge is constructed on liquefiable ground. In this study, we evaluated reduction coefficient of the horizontal subgrade reaction during liquefaction DE based on shaking table tests. We examined the influence of liquefaction resistance factor FL, subgrade shear strain amplitude and velocity of the ground on the reduction coefficient DE from the test results. We made model grounds varying relative soil density in a container, which was placed on a shaking table. A piston was installed on the side wall of the container, and penetration force was measured as horizontal subgrade reaction when the piston was penetrated into the liquefied soil
Is CP Violation Observable in Long Baseline Neutrino Oscillation Experiments ?
We have studied CP violation originated by the phase of the neutrino mixing
matrix in the long baseline neutrino oscillation experiments. The direct
measurements of CP violation is the difference of the transition probabilities
between CP-conjugate channels. In those experiments, the CP violating effect is
not suppressed if the highest neutrino mass scale is taken to be 1\sim 5 \eV,
which is appropriate for the cosmological hot dark matter. Assuming the
hierarchy for the neutrino masses, the upper bounds of CP violation have been
caluculated for three cases, in which mixings are constrained by the recent
short baseline ones. The calculated upper bounds are larger than ,
which will be observable in the long baseline accelerator experiments. The
matter effect, which is not CP invariant, has been also estimated in those
experiments.Comment: 28 pages, LaTex file, 6 figures included using epsfig Matter effect
is estimated(Figs.3(a) (b)). Physical parameters are change
CP Violation in Bilarge Lepton Mixing
We propose a scheme of lepton mixing in which the unitary matrix that
diagonalizes the neutrino mass matrix is bimaximal and the deviation from
bimaximal of the lepton mixing matrix is due to the unitary matrix that
diagonalizes the charged-lepton mass matrix. This matrix is assumed to be
hierarchical, like the quark mixing matrix. It is shown that in general it is
possible to have a sizable value for |U_{e3}| together with an effective
two-neutrino maximal mixing in solar neutrino experiments. If the effective
mixing in solar neutrino experiments is less than maximal, as indicated by
current data, |U_{e3}| is bounded from below. Furthermore, in general the
violation of CP could be relatively large.Comment: 11 pages. Final version to be published in PR
Deviation of Neutrino Mixing from Bi-maximal
We have studied how observables of the neutrino mixing matrix can link up
with the ones in the quark sector. The deviation from the bi-maximal flavor
mixing is parameterized using a 3 x 3 unitary matrix. The neutrino mixings are
investigated supposing this unitary matrix to be hierarchical like the quark
mixing matrix. We obtain the remarkable prediction |U_{e3}| >= 0.03 from the
experimentally allowed range tan^2 theta_{sol} = 0.24 ~ 0.89. The CP violation
in neutrino oscillations is expected to be very small.Comment: Some references are adde
Natural Neutrino Mass Matrix
Naturalness of the neutrino mass hierarchy and mixing is studied. First we
select among 12 neutrino mixing patterns a few patterns, which could form the
natural neutrino mass matrix. Further we show that if the Dirac neutrino mass
matrix is taken as the natural one in the quark sector, then only two mixing
patterns without the large mixing lead to the natural right-handed Majorana
mass matrix. The rest of the chosen patterns with three degenerate mass
solution lead to the unnatural right-handed Majorana mass matrix in the see-saw
mechanism. Notice however, that for the chosen two natural patterns there could
be a huge mass hierarchy such as in order to reproduce
the inverse mass hierarchy of the light neutrinos.Comment: 31 pages, LaTex file, no figures, arguments made more clear, main
conclusions unchanged, version accepted for publication in PRD Reort-no:
Lund-Mph-97/14 Revise
Mu-tau antisymmetry and neutrino mass matrices
Using the seesaw mechanism and a discrete symmetry, we construct a class of
models for the neutrino mass matrix where the inverse of that matrix is the sum
of a mu-tau antisymmetric background and a perturbation. We consider various
possibilities for that perturbation. The simplest possible perturbations lead
to four-parameter neutrino mass matrices which are unable to fit the
experimental data. More complicated perturbations give rise to viable
six-parameter mass matrices; we present detailed predictions of each of them.Comment: 15 pages of text, 7 figure
Lepton Flavor Model from Delta(54) Symmetry
We present the lepton flavor model with , which appears
typically in heterotic string models on the orbifold. Our model
reproduces the tri-bimaximal mixing in the parameter region around degenerate
neutrino masses or two massless neutrinos. We predict the deviation from the
tri-bimaximal mixing by putting the experimental data of neutrino masses in the
normal hierarchy of neutrino masses. The upper bound of is
0.01. There is the strong correlation between and .
Unless is deviated from the maximal mixing considerably,
remains to be tiny.Comment: 19 pages, 7 figures; some discussions are modifie
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