2,451 research outputs found
Quark Mixings in and Suppression of
The quark mixing matrix is studied in depth on the basis of
superstring inspired model with global flavor symmetries.
The sizable mixings between right-handed down-type quark and colored
Higgs field potentially occur but no such mixings in up-type quark
sector. In the model the hierarchical pattern of is understood
systematically. It is shown that due to large - mixings is
naturally suppressed compared to . It is pointed out that the observed
suppression of is in favor of the presence of gauge symmetry
but not in accord with generic SU(5) GUT.Comment: 10pages with no figure, Latex fil
Quantization of the scalar field in a static quantum metric
We investigate the Hamiltonian formulation of quantum scalar fields in a
static quantum metric. We derive a functional integral formula for the
propagator. We show that the quantum metric substantially changes the behaviour
of the scalar propagator and the effective Yukawa potential.Comment: Latex, 12 page
The \Phi^4 quantum field in a scale invariant random metric
We discuss a D-dimensional Euclidean scalar field interacting with a scale
invariant quantized metric. We assume that the metric depends on d-dimensional
coordinates where d<D. We show that the interacting quantum fields have more
regular short distance behaviour than the free fields. A model of a Gaussian
metric is discussed in detail. In particular, in the \Phi^4 theory in four
dimensions we obtain explicit lower and upper bounds for each term of the
perturbation series. It turns out that there is no coupling constant
renormalization in the \Phi^4 model in four dimensions. We show that in a
particular range of the scale dimension there are models in D=4 without any
divergencies
Phenomenology of Neutrino Mass Matrix
The search for possible mixing patterns of charged leptons and neutrinos is
important to get clues of the origin of nearly maximal mixings, since there are
some preferred bases of the lepton mass matrices given by underlying theories.
We systematically examine the mixing patterns which could lead to large lepton
mixing angles. We find out 37 mixing patterns are consistent with experimental
data if taking into account phase factors in the mixing matrices. Only 6
patterns of them can explain the observed data without any tuning of
parameters, while the others need particular choices for phase values.Comment: revised reference
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 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 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 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
5D seesaw, flavor structure, and mass textures
In the 5D theory in which only 3 generation right-handed neutrinos are in the
bulk, the neutrino flavor mixings and the mass spectrum can be constructed
through the seesaw mechanism. The 5D seesaw is easily calculated just by a
replacement of the
Majorana mass eigenvalues, M_i, by 2 M_*tan(h)[\pi RM_i] (M_*: 5D Planck
scale,
R: compactification radius). The 5D features appear when the bulk mass, which
induces the 4D Majorana mass, is the same as the compactification scale or
larger than it. Depending on the type of bulk mass, the seesaw scales of the 3
generations are strongly split (the tan-function case) or degenerate (the
tanh-function case). In the split case, the seesaw enhancement is naturally
realized. The single right-handed neutrino dominance works in a simple setup,
and some specific mass textures, which are just assumptions in the 4D setup,
can be naturally obtained in
5 dimensions. The degenerate case is also useful for a suitable neutrino
flavor structure.Comment: 15 page
Fermion Masses and Mixings in a String Inspired Model
In the context of Calabi-Yau string models we explore the origin of
characteristic pattern of quark-lepton masses and the CKM matrix. The discrete
-symmetry is introduced and the is assigned to the
-parity. The gauge symmetry at the string scale, , is
broken into the standard model gauge group at a very large intermediate energy
scale. At energies below the intermediate scale down-type quarks and also
leptons are mixed with unobserved heavy states, respectively. On the other
hand, there are no such mixings for up-type quarks. Due to the large mixings
between light states and heavy ones we can derive phenomenologically viable
fermion mass hierarchies and the CKM matrix. Mass spectra for
intermediate-scale matter beyond the MSSM are also determined. Within this
framework proton lifetime is long enough to be consistent with experimental
data. As for the string scale unification of gauge couplings, however,
consistent solutions are not yet found.Comment: 49 pages, 1 figure, Latex Revised version includes discussion on FCNC
problems. Final version to appear in Prog. Theor. Phys. Vol.96 No.
Thermal leptogenesis in a supersymmetric neutrinophilic Higgs model
We investigate thermal leptogenesis in a supersymmetric neutrinophilic Higgs
model by taking phenomenological constraints into account, where, in addition
to the minimal supersymmetric standard model, we introduce an extra Higgs field
with a tiny vacuum expectation value (VEV) which generates neutrino masses.
Thanks to this tiny VEV of the neutrinophilic Higgs, our model allows to reduce
the mass of the lightest right-handed (s)neutrino to be GeV as
keeping sufficiently large CP asymmetry in its decay. Therefore, the reheating
temperature after inflation is not necessarily high, hence this scenario is
free from gravitino problem.Comment: 5 pages, 1 figur
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