5,097 research outputs found

### Possibility of the LBL experiment with the high intensity proton accelerator

We study physics possibility of Very Long Base-Line (VLBL)
Neutrino-Oscillation Experiments with the High Intensity Proton Accelerator,
which will be completed by the year 2007 in Tokai-village, Japan. As a target,
a 100 kton-level water-Cerenkov detector is considered at 2,100 km away.
Assuming the pulsed narrow-band nu_mu beams, we study sensitivity of such
experiments to the neutrino mass hierarchy, the mass-squared differences, one
CP phase and three angles of the lepton-flavor-mixing matrix. We find that
experiments at a distance 2,100 km can determine the neutrino mass hierarchy if
the mixing matrix element U_{e3} is not too small. The CP phase and U_{e3} can
be constrained if the large-mixing-angle solution of the solar-neutrino deficit
is realized.Comment: 3 pages, 1 figure Proceedings of the NuFACT'01 Workshop, Tsukuba,
Japan, May 200

### Generic Relations of Flavor Mixings between Leptons and Quarks in SU(5)

We have studied implications of the generic lopsided mass matrix of the
charged leptons by taking the SU(5) GUT relation in the nearest-neighbor
interaction (NNI) basis. We have found four interesting relations among the
lepton mixings and the quark ones, which are independent of details of the
model. These relations are discussed by using the experimental data. We have
also discussed the relation between U_{e2} and U_{e3} incuding the contribution
from the neutrino mass matrix. We have presented the probable value U_{e3}=0.05
\sim 0.16, which is independent of the solar neutrino solutions. The CP
violating quantity J_{CP} is also discussed.Comment: 16 pages, 2 figures, Some discussions are modified, but results are
not change

### The effects of Majorana phases in three-generation neutrinos

Neutrino-oscillation solutions for the atmospheric neutrino anomaly and the
solar neutrino deficit can determine the texture of the neutrino mass matrix
according to three types of neutrino mass hierarchies as Type A: $m_1^{} \ll
m_2^{} \ll m_3^{}$,
Type B: $m_1^{} \sim m_2^{} \gg m_3^{}$, and Type C: $m_1^{} \sim m_2^{} \sim
m_3^{}$, where $m_i$ is the $i$-th generation neutrino absolute mass. The
relative sign assignments of neutrino masses in each type of mass hierarchies
play the crucial roles for the stability against quantum corrections. Actually,
two physical Majorana phases in the lepton flavor mixing matrix connect among
the relative sign assignments of neutrino masses. Therefore, in this paper we
analyze the stability of mixing angles against quantum corrections according to
three types of neutrino mass hierarchies (Type A, B, C) and two Majorana
phases. Two phases play the crucial roles for the stability of the mixing
angles against the quantum corrections.Comment: LaTeX2e, 15 pages, 8 figure

### Analytic Solutions to the RG Equations of the Neutrino Physical Parameters

In the case of two generation neutrinos, the energy-scale dependence of the
lepton-flavor mixing matrix with Majorana phase can be governed by only one
parameter r, which is the ratio between the diagonal elements of neutrino mass
matrix. By using this parameter r, we derive the analytic solutions to the
renormalization group equations of the physical parameters, which are the
mixing angle, Majorana phase, and the ratio of the mass-squared difference to
the mass squared of the heaviest neutrino. The energy-scale dependence of the
Majorana phase is clarified by using these analytic solutions. The instability
of the Majorana phase causes in the same parameter region in which the mixing
angle is unstable against quantum corrections.Comment: LaTeX2e, 9 pages, 6 figure

### Energy-Scale Dependence of the Lepton-Flavor-Mixing Matrix

We study an energy-scale dependence of the lepton-flavor-mixing matrix in the
minimal supersymmetric standard model with the effective dimension-five
operators which give the masses of neutrinos. We analyze the renormalization
group equations of kappa_{ij}s which are coefficients of these effective
operators under the approximation to neglect the corrections of O(\kappa^2). As
a consequence, we find that all phases in $\kappa$ do not depend on the
energy-scale, and that only n_g-1 (n_g: generation number) real independent
parameters in the lepton-flavor-mixing matrix depend on the energy-scale.Comment: 6 pages, no figur

### The effect of Majorana phase in degenerate neutrinos

There are physical Majorana phases in the lepton flavor mixing matrix when
neutrinos are Majorana fermions. In the case of two degenerate neutrinos, the
physical Majorana phase plays the crucial role for the stability of the maximal
flavor mixing between the second and the third generations against quantum
corrections. The physical Majorana phase of $\pi$ guarantees the maximal mixing
to be stable against quantum corrections, while the Majorana phase of zero lets
the maximal mixing be spoiled by quantum corrections when neutrino masses are
of O(eV). The continuous change of the Majorana phase from $\pi$ to 0 makes the
maximal mixing be spoiled by quantum corrections with O(eV) degenerate neutrino
masses. On the other hand, when there is the large mass hierarchy between
neutrinos, the maximal flavor mixing is not spoiled by quantum corrections
independently of the Majorana phase.Comment: 7 pages, 1 figures, LaTe

### Measuring the CP-violating phase by a long base-line neutrino experiment with Hyper-Kamiokande

We study the sensitivity of a long-base-line (LBL) experiment with neutrino
beams from the High Intensity Proton Accelerator (HIPA), that delivers 10^{21}
POT per year, and a proposed 1Mt water-Cherenkov detector, Hyper-Kamiokande
(HK) 295km away from the HIPA, to the CP phase (delta_{M N S}) of the
three-flavor lepton mixing matrix. We examine a combination of the nu_mu
narrow-band beam (NBB) at two different energies, vev{p_pi}=2, 3GeV, and the
bar{nu}_mu NBB at vev{p_pi}=2GeV. By allocating one year each for the two nu_mu
beams and four years for the bar{nu}_mu beam, we can efficiently measure the
nu_mu to nu_e and bar{nu}_mu to bar{nu}_e transition probabilities, as well as
the nu_mu and bar{nu}_mu survival probabilities. CP violation in the lepton
sector can be established at 4sigma (3sigma) level if the MSW
large-mixing-angle scenario of the solar-neutrino deficit is realized, |\dmns|
or |delta{M N S}-180^{circ}| > 30^{circ}, and if 4|U_{e3}|^2 (1-|U_{e3}|^2)
equiv sin^2 2 theta_{CHOOZ} > 0.03 (0.01). The phase delta_{M N S} is more
difficult to constrain by this experiment if there is little CP violation,
delta_{M N S} sim 0^{circ} or 180^{circ}, which can be distinguished at 1sigma
level if sin^2 2 theta_{CHOOZ} >~ 0.01.Comment: 16 pages, 4 figures, 2 tables, we add 1 figure, some refrences, and
minor corrections. PLB published versio

### Are lepton flavor mixings in the democratic mass matrix stable against quantum corrections?

We investigate whether the lepton flavor mixing angles in the so-called
democratic type of mass matrix are stable against quantum corrections or not in
the minimal supersymmetric standard model with dimension five operator which
induces neutrino mass matrix. By taking simple breaking patterns of $S_3{}_L
\times S_3{}_R$ or $O(3)_L \times O(3)_R$ flavor symmetries and the scale where
democratic textures are induced as $O(10^{13})$ GeV, we find that the stability
of the lepton flavor mixing angles in the democratic type of mass matrix
against quantum corrections depends on the solar neutrino solutions. The
maximal flavor mixing of the vacuum oscillation solution is spoiled by the
quantum corrections in the experimental allowed region of $\tan \beta$. The
large angle MSW solution is spoiled by the quantum corrections in the region of
$\tan \beta > 10$. The condition of $\tan \beta \leq 10$ is needed in order to
obtain the suitable mass squared difference of the small angle MSW solution.
These strong constraints must be regarded for the model building of the
democratic type of mass matrixComment: 12pages,LaTe

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