Universal Seesaw Mass Matrix Model
and SO(10) \times SO(10) Unification
The universal seesaw mass matrix model contains
extra fermions F_{iL}=(1,1) and F_{iR}=(1,1) (i=1,2,3:
family numbers) in addition to the conventional quarks
and leptons f_{iL}=(2,1) and f_{iR}=(1,2) of SU(2)_L
\times SU(2)_R, but the meaning of F_L and F_R in the
unification scenario is not yet clear in spite of the
phenomenological success of the model. As a candidate
of the unification scenarios which offer the rooms to
F_L and F_R, an idea that those fermions (f_L, F_R^c)
and (f_R, F_L^c) are assigned to (16,1) and (1,16) of
SO(10)_L\times SO(10)_R is examined by investigating
the possible symmetry breaking pattern and its intermediate
mass scales.
US-98-06 / AMU-98-06
revised version
Universal Seesaw Mass Matrix Model
with Three Light Psendo-Dirac Neutrinos
Yoshio Koide and Hideo Fusaoka
A universal seesaw mass matrix model, which gives successful
description of quark mass matrix in terms of lepton masses,
yields three ``sterile" neutrinos \nu^s_{i}, which compose
pseudo-Dirac neutrinos \nu_{i\pm}^{ps}\simeq (\nu_{i} \pm
\nu^s_{i})/\sqrt{2} together with the active neutrinos \nu_{i}
(i=e,\mu,\tau). The solar and atmospheric neutrino data are
explained by the mixings \nu_{e}\leftrightarrow \nu^s_{e} and
\nu_{\mu}\leftrightarrow \nu^s_{\mu}, respectively.
In spite of such observations of the large mixing
\sin^2 2\theta\simeq 1 in the disappearance experiments,
effective mixing parameters \sin^2 2\theta^{\alpha\beta}
in appearance experiments \nu_\alpha\rightarrow\nu_\beta
(\alpha, \beta = e, \mu, \tau) are highly suppressed.
Contributed paper to XVIII International Conference on Neutrino Physics
and Astrophysics (presented at the poster session), Takayama, Japan, June 4-9, 1998.
Universal Seesaw Mass Matrix Model and Neutrino Phenomenology
Stimulated by the recent development of the "universal seesaw mass matrix model",
and application of the model to the neutrino mass matrix is investigated:
For the charged lepton and down-quark sectors, the model explains the smallness
of their masses mf by the conventional seesaw mechanism m_f \simeq m_L M_f^{-1} m_R
(M_f is a mass matris of hypothetical heavy fermions F).
On the other hand, the observed fact m_t \sim \Lambda_L (electroweak scale \Lambda_L =174 GeV)
seems to reject the applying of the seesaw mechanism to the up-quark sector.
However, recently, it has been found that, by taking det M_f=0 for the up-quark
sector F=U, we can understand the question of why only top quark has a mass of
the order of \Lambda_L without the sesaw-suppression factor O(m_R)/O(M_f). For neutrino
sectorm the mass matrix M_nu is given by M_nu \simeq m_L M_f^{-1} m_f^T (F=N), so that
the masses m_nu are suppressed by a factor O(m_R)/O(M_f) compared with the conventional
quark and charged lepton masses. The model can naturally lead to a large mixing .
Also another model is investigated within the framework of the universal seesaw
model: the model leads to three sets of the almost degenerate two Majorana neutrinos
which are large mixing states between the left-handed neutrinos and SU(2)L*SU(2)R
singlet neutrinos , so that the model can give a simultaneous explanation of
the atmospheric and solar neutrino data.
Invited talk at the Workshop on Fermision Mass and Cp Violation, Higashi-Hiroshima, Japan, March 5-6, 1998.
New Aspects on Seesaw Mass Matrix Model
Recent development of the universal see sawmass matrix model is reviewed. The mode l was proposed in order to explain why quark and lepton masses are so small compared with the electroweak scale L=h0Li=174 GeV. However, the recently observed top-quark mass mt'180 GeV seems to make an objection against the seesaw mass picture. For this problem, it has recently pointed out that the seesaw mass matrix model is rather favorable to the fact mtL if we consider the model with detMF=0 for up-quark sector, where MF is a 33 mass matrix of hypothetical heavy fermions F.The model can give a natural explanation why only top-quark acquire the mass of the order of L. The model with detMU=0 offers abundant new physics to us(e.g.,the fourth up-quark t0, FCNC, and so on).
Coupling Constants Evolution in a Universal
Seesaw Mass Matrix Model
Stimulated by a universal seesaw mass matrix model which can
successfully give quark masses and CKM matrix elements in terms
of charged lepton masses, the evolution of the seesaw mass matrices
is investigated. Especially, an investigation is made as to whether
this evolution can constrain the necessary intermediate scales
in these types of models and its vaiability. energy scale at which
the