269,849 research outputs found

### Neutrino, Lepton, and Quark Masses in Supersymmetry

The recently proposed model of neutrino mass with no new physics beyond the
TeV energy scale is shown to admit a natural and realistic supersymmetric
realization, when combined with another recently proposed model of quark masses
in the context of a softly broken U(1) symmetry. Four Higgs doublets are
required, but two must have masses at the TeV scale. New characteristic
experimental predictions of this synthesis are discussed.Comment: 7 pages, no figur

### Neutrino Mass from Triplet and Doublet Scalars at the TeV Scale

If the minimal standard model of particle interactions is extended to include
a scalar triplet with lepton number $L=-2$ and a scalar doublet with $L=-1$,
neutrino masses $m_\nu \sim \mu_{12}^4 v^2/M^5 \sim 10^{-2}$ eV is possible,
where $v \sim 10^2$ GeV is the electroweak symmetry breaking scale, $M \sim 1$
TeV is the typical mass of the new scalars, and $\mu_{12} \sim 1$ GeV is a soft
lepton-number-violating parameter.Comment: 6 pages, no figur

### Lepton Family Symmetry and Neutrino Mass Matrix

The standard model of leptons is extended to accommodate a discrete Z_3 X Z_2
family symmetry. After rotating the charged-lepton mass matrix to its diagonal
form, the neutrino mass matrix reveals itself as very suitable for explaining
atmospheric and solar neutrino oscillation data. A generic requirement of this
approach is the appearance of three Higgs doublets at the electroweak scale,
with observable flavor violating decays.Comment: 9 pages, including 1 figur

### Triplicity of Quarks and Leptons

Quarks come in three colors and have electric charges in multiples of
one-third. There are also three families of quarks and leptons. Whereas the
first two properties can be understood in terms of unification symmetries such
as SU(5), SO(10), or E_6, why there should only be three families remains a
mystery. I propose how all three properties involving the number three are
connected in a fivefold application of the gauge symmetry SU(3).Comment: 10 pages, including 2 figure

### Plato's Fire and the Neutrino Mass Matrix

With the accumulation of many years of solar and atmospheric neutrino
oscillation data, the approximate form of the 3 X 3 neutrino mixing matrix is
now known. The theoretical challenge is to understand where this mixing matrix
comes from. Recently, a remarkable fact was discovered that for a specific
pattern of the neutrino mass matrix at a high scale, any flavor-changing
radiative correction will automatically lead to the desired mixing matrix. It
was also discovered that the required specific pattern at the high scale can be
maintained by the non-Abelian discrete symmetry A_4 which is also the symmetry
group of the regular tetrahedron, one of five perfect geometric solids known to
Plato who associated it with the element ``fire''. I discuss this recent
development and add to it a new and very simple mechanism for the
implementation of the flavor-changing radiative correction.Comment: 12 pages, to appear as a Brief Review in MPL

### Nearly Mass-Degenerate Majorana Neutrinos: Double Beta Decay and Neutrino Oscillations

Assuming equal tree-level Majorana masses for the standard-model neutrinos,
either from the canonical seesaw mechanism or from a heavy scalar triplet, I
discuss how their radiative splitting may be relevant to neutrinoless double
beta decay and neutrino oscillations.Comment: 12 pages, including 4 figures, talk at NANP9

### New "Square Root" Model of Lepton Family Cyclic Symmetry

Following the newly formulated notion of form invariance of the neutrino mass
matrix, a complete model of leptons is constructed. It is based on a specific
unitary 3 X 3 matrix U in family space, such that U^2 is the simple discrete
symmetry nu_e to -nu_e, nu_mu to nu_tau. Thus U also generates the cyclic group
Z_4. The charged-lepton mass matrix is nearly diagonal while the neutrino mass
matrix is of the form suitable for explaining maximal (large) mixing in
atmospheric (solar) neutrino oscillations in the context of three nearly
degenerate neutrino masses. Observable lepton flavor violation is predicted.
Quarks may be treated in the same way as the charged leptons.Comment: 10 pages, no figur

### Decay of Z into Three Pseudoscalar Bosons

We consider the decay of the $Z$ boson into three pseudoscalar bosons in a
general two-Higgs-doublet model. Assuming $m_A$ to be very small, and that of
the two physical neutral scalar bosons $h_1$ and $h_2$, $A$ only couples to $Z$
through $h_1$, we find the $Z \to A A A$ branching fraction to be negligible
for moderate values of $\tan \beta \equiv v_2/v_1$, if there is no $\lambda_5
(\Phi_1^\dagger \Phi_2)^2 + h.c.$ term in the Higgs potential; otherwise there
is no absolute bound but very large quartic couplings (beyond the validity of
perturbation theory) are needed for it to be observable.Comment: 8 pages including 1 fi

### Supersymmetric U(1) Gauge Realization of the Dark Scalar Doublet Model of Radiative Neutrino Mass

Adding a second scalar doublet (eta^+,eta^0) and three neutral singlet
fermions N_{1,2,3} to the Standard Model of particle interactions with a new
Z_2 symmetry, it has been shown that Re(eta^0) or Im(eta^0) is a good
dark-matter candidate and seesaw neutrino masses are generated radiatively. A
supersymmetric U(1) gauge extension of this new idea is proposed, which
enforces the usual R parity of the Minimal Supersymmetric Standard Model, and
allows this new Z_2 symmetry to emerge as a discrete remnant.Comment: 8 pages, 3 figure

### Utility of a Special Second Scalar Doublet

This Brief Review deals with the recent resurgence of interest in adding a
second scalar doublet (eta^+,eta^0) to the Standard Model of particle
interactions. In most studies, it is taken for granted that eta^0 should have a
nonzero vacuum expectation value, even if it may be very small. What if there
is an exactly conserved symmetry which ensures =0? The phenomenological
ramifications of this idea include dark matter, radiative neutrino mass,
leptogenesis, and grand unification.Comment: 9 pages, 1 figur

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