US-02-11; CERN-TH/2002-274;SUTpp-02-171
An SU(5) SUSY Model with R-Parity Violation
and Radiatively Induced Neutrino Masses
Yoshio Koide and Joe Sato
The radiatively induced neutrino mass matrix is investigated
on the basis of an SU(5) SUSY model.
In order to evade the proton decay, an ansatz based on
a discrete symmetry Z_2 is assumed:
although, at the unification scale, we have two types of superfields
\Psi_{L(\pm)}=\overline{5}_{L(\pm)}+10_{L(\pm)}, which are
transformed as
\Psi_{L(\pm)} \rightarrow \pm \Psi_{L(\pm)} under the discrete
symmetry Z_2, the particles \Psi_{L(+)}
are decoupled after the SU(5) symmetry is broken, so that
our quarks and leptons belong to \Psi_{L(-)}.
The R-parity-violating terms for our quarks and leptons \Psi_{L(-)}
are basically forbidden under the symmetry Z_2.
However, we assume that mixings between members of \Psi_{L(+)}
and those of \Psi_{L(-)} are in part caused after SU(5) is broken.
As a result, the R-parity-violating interactions are in part
allowed, so that the neutrino masses are radiatively generated,
while the proton decay due to the R-parity violating terms is
still forbidden because the term d_R^c d_R^c u_R^c has z=-1.
US-02-10; CERN-TH/2002-251
Phy.Rev.D66, 093006 (2002)
Universal Texture of Quark and Lepton Mass Matrices
and a Discrete Symmetry Z_3
Yoshio Koide, Hiroyuki Nishiura, Koichi Matsuda, Tatsuru Kikuchi and
Takeshi Fukuyama
Recent neutrino data have been favourable to a nearly bimaximal mixinRecent neutrino data have been favourable to a nearly bimaximal mixing,
which suggests a simple form of the neutrino mass matrix.
Stimulated by this matrix form, a possibility that all the mass
matrices of quarks and leptons have the same form as in the
neutrinos is investigated.
The mass matrix form is constrained by a discrete symmetry Z_3 and
a permutation symmetry S_2.
The model, of course, leads to a nearly bimaximal mixing
for the lepton sectors, while, for the quark sectors, it can lead to
reasonable values of the CKM mixing matrix and masses.
g,
which suggests a simple form of the neutrino mass matrix.
Stimulated by this matrix form, a possibility that all the mass
matrices of quarks and leptons have the same form as in the
neutrinos is investigated.
The mass matrix form is constrained by a discrete symmetry Z_3 and
a permutation symmetry S_2.
The model, of course, leads to a nearly bimaximal mixing
for the lepton sectors, while, for the quark sectors, it can lead to
reasonable values of the CKM mixing matrix and masses.
US-02-09; CERN-TH/2002-36;AMU-02-09
Phy.Rev.D66, 113004 (2002)
Unified Description of Quark and Lepton Mass Matrices
in a Universal Seesaw Model
Yoshio Koide and Hideo Fusaoka
In the democratic universal seesaw model, the mass matrices
are given by
\overline{f}_L m_L F_R + \overline{F}_L m_R f_R +
\overline{F}_L M_F F_R (f: quarks and leptons; F: hypothetical
heavy fermions), m_L and m_R are universal for up- and
down-fermions, and M_F has a structure ({\bf 1}+ b_f X)
(b_f is a flavour-dependent parameter, and X is a democratic
matrix). The model can successfully explain the quark
masses and CKM mixing parameters in terms of the charged lepton
masses by adjusting only one parameter, b_f.
However, so far, the model has not been able to
give the observed bimaximal mixing for the neutrino sector.
In the present paper, we consider that M_F in the quark sectors
are still ``fully" democratic, while M_F in the lepton sectors are
partially democratic. Then, the revised model can reasonably give
a nearly bimaximal mixing without spoiling the previous
success in the quark sectors.
Contribution paper to ICHEP 2002 at Amsterdam
A Unified Description of Quark and Lepton Mass Matrices
in a Universal Seesaw Model
Yoshio Koide and Hideo Fusaoka
In a framework of the universal seesaw model which intends to
give a unified description of the quark and lepton mass matrices
by assuming a seesaw mechanism not only for the neutrinos but
also for the charged leptons and quarks, a possible form of the
neutrino mass matrix is investigated. In the mass matrices
\overline{f}_L m_L F_R + \overline{F}_L m_R f_R +\overline{F}_L M_F F_R
(f: quarks and leptons; F: hypotheticalheavy fermions), m_L and m_R
are universal for up- and down-fermions, and M_F have only fermion-sector-dependent
structures. The observed top quark mass enhancement is understood
by detM_F =0 (F=U).
The quark and lepton masses and mixings (including the neutrino sector)
are well-satisfactorily described by only one complex parameter
b_f in M_F which is invariant under a permutation symmetry S_3,
i.e., b_e=0, b_\nu=-2/3, b_u=-1/3 and b_d=-e^{i\beta}
(\beta=18^\circ),
when m_L and m_R are fixed by using the observed charged lepton
mass values as the inputs.
However, so far, the universal seesaw model has not been able to
give bimaximal mixing for the neutrino sector under the parameters
which well describe the observed masses and mixings of the quarks
and charged leptons, although it can give either maximal mixing of
\nu_e-\nu_\mu or \nu_\mu-\nu_\tau.
In the present paper, we consider that m_L and m_R are universal
for up- and down-fermions, but those in the lepton
sectors are different from those in the quark sectors by a rotation.
The new universal seesaw model can reasonably give the observed
nearly bimaximal mixing.
Contribution paper to ICHEP2002 at Amsterdam
A New Idea to Evade the Proton Decay
in the Extension of the Zee Model to the SUSY GUT
and Possible Forms of the Radiatively-Induced Neutrino Mass Matrix
In order to evade the proton decay which appears when
the Zee model is embedded into a SUSY GUT scenario with
R-parity violation, a new idea based on a discrete symmetry
Z_2 has recently been proposed.
Under the symmetry Z_2, the quark and
lepton mass matrices are tightly constrained. Possible forms
of the radiatively-induced neutrino mass matrix are
systematically investigated.
To be publised in Nucl. Instr. Meth. A (Elsevier)
New Trends in the Zee Model
Recent trends in the Zee model are reviewed.
Especially, the importance of a serious constraint in the Zee
model, \sin^2 2\theta_{solar} =1.0, is pointed out.
Radiatively Induced Neutrino Mass Matrix
in an SUSY GUT Model with R-Parity Violation
Yoshio Koide and Ambar Ghosal
In order to evade the proton decay which appears when
the Zee model is embedded into a SUSY GUT scenario with
R-parity violation, a new idea based on a discrete
Z_2 symmetry is proposed. Under the symmetry Z_2,
the quark and
lepton mass matrices are tightly constrained.
The admissible form
of the radiatively-induced neutrino mass matrix
is investigated.
Presented at KEKTC5 (Nov. 2001)
Nucl. Phys. B (Proc. SUppl.) 111 294 (2002), (Elsevier)
Prospects of the Zee model
The Zee model is one of promising models of neutrino mass
generation mechanism. However, the original Zee model is
not on the framework of the grand unification scenario, and
moreover, it is recently pointed out that the predicted value
of sin^2 2\theta_{solar} must be satisfied the relation
sin^2 2\theta_{solar} > 0.99. We discuss whether possible
GUT versions of the Zee model can be free from the severe
constraint sin^2 2\theta_{solar} > 0.99 or not. We will
conclude that the following two models are promising: an
R-parity violating SUSY GUT model and an SO(10) model with
a 126-plet scalar.