3,720 research outputs found
Z_3 Dark Matter and Two-Loop Neutrino Mass
Dark matter is usually distinguished from ordinary matter by an odd-even
parity, i.e. the discrete symmetry Z_2. The new idea of Z_3 dark matter is
proposed with a special application to generating radiative Majorana neutrino
masses in two-loop order.Comment: expanded (9 pages, 2 figures), 2 references adde
Theoretical Expectations for Rare and Forbidden Tau Decays
Given the experimental evidence for oscillations, the
existence of lepton flavor violation in decays is a theoretical
certainty. In this brief review, I consider the connection between models of
neutrino mass and the expected observability of some decays.Comment: Talk at TAU 02 (Santa Cruz, CA
Near Tribimaximal Neutrino Mixing with Delta(27) Symmetry
The discrete subgroup Delta(27) of SU(3) has the interesting multiplication
rule 3 X 3 = bar{3} + bar{3} + bar{3}, which is used to obtain near
tribimaximal neutrino mixing. Using present neutrino oscillation data as input,
this model predicts that the effective mass m_{ee} measured in neutrinoless
double beta decay will be 0.14 eV.Comment: 6 pages, no figur
Dark Scalar Doublets and Neutrino Tribimaximal Mixing from A_4 Symmetry
In the context of A_4 symmetry, neutrino tribimaximal mixing is achieved
through the breaking of A_4 to Z_3 (Z_2) in the charged-lepton (neutrino)
sector respectively. The implied vacuum misalignment of the (1,1,1) and (1,0,0)
directions in A_4 space is a difficult technical problem, and cannot be treated
without many auxiliary fields and symmetries (and perhaps extra dimensions). It
is pointed out here that an alternative scenario exists with A_4 alone and no
redundant fields, if neutrino masses are "scotogenic", i.e. radiatively induced
by dark scalar doublets as recently proposed.Comment: 8 pages, 2 figures, 1 reference and 1 paragraph adde
Neutrino Mass Matrix from S_4 Symmetry
The cubic symmetry S_4 contains A_4 and S_3, both of which have been used to
study neutrino mass matrices. Using S_4 as the family symmetry of a complete
supersymmetric theory of leptons, it is shown how the requirement of breaking
S_4 at the seesaw scale without breaking supersymmetry enforces a special form
of the neutrino mass matrix which exhibits maximal nu_mu - nu_tau mixing as
well as zero U_e3. In addition, (nu_e + nu_mu + nu_tau)/sqrt{3} is naturally
close to being a mass eignestate, thus predicting tan^2 theta_12 to be near but
not equal to 1/2.Comment: 11 pages, no figur
Discrete Symmetry and CP Phase of the Quark Mixing Matrix
A simple specific pattern of the two 3 X 3 quark mass matrices is proposed,
resulting in a prediction of the CP phase of the charged-current mixing matrix
V_CKM, i.e. sin 2 phi_1 (beta) = 0.733, which is in remarkable agreement with
data, i.e. sin 2 phi_1 = 0.728 +/- 0.056 +/- 0.023 from Belle and sin 2 beta =
0.722 +/- 0.040 +/- 0.023 from Babar. This pattern can be maintained by a
discrete family symmetry, an example of which is D_7, the symmetry group of the
heptagon.Comment: 9 pages, no figur
Group and Tri-bimaximal Neutrino Mixing -- A Renormalizable Model
The tetrahedron group has been widely used in studying neutrino mixing
matrix. It provides a natural framework of model building for the tri-bimaximal
mixing matrix. In this class of models, it is necessary to have two Higgs
fields, and , transforming under as 3 with one of them
having vacuum expectation values for the three components to be equal and
another having only one of the components to be non-zero. These specific vev
structures require separating and from communicating with each
other. The clash of the different vev structures for and is the
so called sequestering problem. In this work, I show that it is possible to
construct renormalizable supersymmetric models producing the tri-bimaximal
neutrino mixing with no sequestering problem.Comment: 4 page
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
Classification of Effective Neutrino Mass Operators
We present a classification of SU(3) x SU(2) x U(1) gauge invariant \Delta L
= 2 (L being lepton number) effective operators relevant for generating small
Majorana neutrino masses. Operators of dimension up to 11 have been included in
our analysis. This approach enables us to systematically identify interesting
neutrino mass models. It is shown that many of the well-known models fall into
this classification. In addition, a number of new models are proposed and their
neutrino phenomenology is outlined. Of particular interest is a large class of
models in which neutrinoless double beta decays arise at a lower order compared
to the neutrino mass, making these decays accessible to the current round of
experiments.Comment: 34 pages in RevTeX with 18 figure
Breaking Tri-bimaximal Mixing and Large
The long baseline neutrino experiment, T2K, and the reactor experiment,
Double Chooz will soon present new data. If we expect to be
0.1-0.2, which is close to the present experimental upper bound, we should not
persist in the paradigm of the tri-bimaximal mixing. We discuss breaking the
tri-bimaximal mixing by adding a simple mass matrix, which could be derived
from some non-Abelian discrete symmetries. It is found that
is expected in our model independent analysis of the
generalized mass matrix for the normal or inverted hierarchical neutrino mass
spectrum. On the other hand, and are
expected to be not far from 1/2 and 1/3, respectively. As a typical example, we
also discuss the flavor model with the 1 and 1' flavons, which break the
tri-bimaximal mixing considerably. In this modified version of the Altarelli
and Feruglio model, is predicted to be around 0.15 in the
case of the normal hierarchical neutrino masses , and 0.2 in
the case of the inverted hierarchy . The form of the neutrino
mass matrix looks rather interesting --- it is suggestive of other discrete
symmetries as well.Comment: 10 pages, 12 figures, final versio
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