2,272 research outputs found
Tripartite Neutrino Mass Matrix
The 3 X 3 Majorana neutrino mass matrix is written as a sum of 3 terms, i.e.
M_nu = M_A + M_B + M_C, where M_A is proportional to the identity matrix and
M_B and M_C are invariant under different Z_3 transformations. This M_nu is
very suitable for understanding atmospheric and solar neutrino oscillations,
with sin^2 (2 theta_atm) and tan^2 (theta_sol) fixed at 1 and 0.5 respectively,
in excellent agreement with present data. It has in fact been proposed before,
but only as an ansatz. This paper uncovers its underlying symmetry, thus
allowing a complete theory of leptons and quarks to be constructed.Comment: 9 pages, no figur
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
Measuring cosmogenic Li9 background in a reactor neutrino experiment
Cosmogenic isotopes 9Li and 8He produced in the detector are the most
problematic background in the reactor neutrino experiments designed to
determine precisely the neutrino mixing angle theta13. The average time
interval of cosmic-ray muons in the detector is often on the order of the
lifetimes of the 9Li and 8He isotopes. We have developed a method for
determining this kind of background from the distribution of time since last
muon for muon rate up to about 20 Hz when the background-to-signal ratio is
small, on the order of a few percents.Comment: 9 pages, 3 figures. To appear in NIM
Estimate of neutrino masses from Koide's relation
We apply Koide's mass relation of charged leptons to neutrinos and quarks,
with both the normal and inverted mass schemes of neutrinos discussed. We
introduce the parameters , and to describe the deviations
of neutrinos and quarks from Koide's relation, and suggest a quark-lepton
complementarity of masses such as . The masses of neutrinos are determined from the improved relation, and they
are strongly hierarchical (with the different orders of magnitude of , , and ).Comment: 12 latex pages, 4 figures, version in publicatio
A New Parametrization of the Neutrino Mixing Matrix
The neutrino mixing matrix is expanded in powers of a small parameter
, which approximately equals to 0.1. The meaning of every order of the
expansion is discussed respectively, and the range of is carefully
calculated. We also present some applications of this new parametrization, such
as to the expression of the Jarlskog parameter , in which the simplicities
and advantages of this parametrization are shown.Comment: 11 pages, 4 figures, version published in PL
Inverse seesaw and dark matter in models with exotic lepton triplets
We show that models with exotic leptons transforming as E ~ (1,3,-1) under
the standard model gauge symmetry are well suited for generating neutrino mass
via a radiative inverse seesaw. This approach realizes natural neutrino masses
and allows multiple new states to appear at the TeV scale. The exotic leptons
are therefore good candidates for new physics that can be probed at the LHC.
Furthermore, remnant low-energy symmetries ensure a stable dark matter
candidate, providing a link between dark matter and the origins of neutrino
mass.Comment: 6 pages, 3 figures (revtex4.1, two-columns
Generalized Tri-bimaximal Neutrino Mixing and Its Sensitivity to Radiative Corrections
We argue that the tri-bimaximal neutrino mixing pattern or its
generalized form , which includes two arbitrary Majorana phases of CP
violation, may result from an underlying flavor symmetry at a superhigh energy
scale close to the seesaw scale ( GeV). Taking the working
assumption that three neutrino masses are nearly degenerate, we calculate
radiative corrections to and in their evolution down to the
electroweak scale ( GeV). Three mixing angles of or are
essentially stable against radiative corrections in the standard model (SM). In
the minimal supersymmetric standard model (MSSM), however, is in general
disfavored and can be compatible with current neutrino oscillation data
if its two Majorana phases and are properly
fine-tuned. We also find that it is possible to radiatively generate the
CP-violating phase from and , and \delta
may keep on staying at its fixed point in either the SM or the MSSM.Comment: RevTex 14 pages, 2 figures. Table I corrected. Minor changes made.
More discussions adde
Searching for Secluded Dark Matter via Direct Detection of Recoiling Nuclei as well as Low Energy Electrons
Motivated by recent cosmic ray experimental results there has been a
proposition for a scenario where a secluded dark matter particle annihilates,
primarily, into Standard Model leptons through a low mass mediator particle. We
consider several varieties of this scenario depending on the type of mixing
among gauge bosons and we study the implications in novel direct dark matter
experiments for detecting low energy recoiling electrons. We find significant
event rates and time modulation effects, especially in the case where the
mediator is massless, that may be complementary to those from recoiling nuclei.Comment: 27 pages, references added, published versio
Antibodies to the Mr 64,000 (64K) protein in islet cell antibody positive non-diabetic individuals indicate high risk for impaired Beta-cell function
A prospective study of a normal childhood population identified 44 islet cell antibody positive individuals. These subjects were typed for HLA DR and DQ alleles and investigated for the presence of antibodies to the Mr 64,000 (64K) islet cell antigen, complement-fixing islet cell antibodies and radiobinding insulin autoantibodies to determine their potency in detecting subjects with impaired Beta-cell function. At initial testing 64K antibodies were found in six of 44 islet cell antibody positive subjects (13.6%). The same sera were also positive for complement-fixing islet cell antibodies and five of them had insulin autoantibodies. During the follow-up at 18 months, islet cell antibodies remained detectable in 50% of the subjects studied. In all six cases who were originally positive, 64K antibodies were persistently detectable, whereas complement-fixing islet cell antibodies became negative in two of six and insulin autoantibodies in one of five individuals. HLA DR4 (p < 0.005) and absence of asparic acid (Asp) at position 57 of the HLA DQ chain (p < 0.05) were significantly increased in subjects with 64K antibodies compared with control subjects. Of 40 individuals tested in the intravenous glucose tolerance test, three had a first phase insulin response below the first percentile of normal control subjects. Two children developed Type 1 (insulin-dependent) diabetes mellitus after 18 and 26 months, respectively. Each of these subjects was non-Asp homozygous and had persistent islet cell and 64K antibodies. We conclude that 64K antibodies, complement-fixing islet cell antibodies and insulin autoantibodies represent sensitive serological markers in assessing high risk for a progression to Type 1 diabetes in islet cell antibody positive non-diabetic individuals
Accidental stability of dark matter
We propose that dark matter is stable as a consequence of an accidental Z2
that results from a flavour-symmetry group which is the double-cover group of
the symmetry group of one of the regular geometric solids. Although
model-dependent, the phenomenology resembles that of a generic Higgs portal
dark matter scheme.Comment: 12 pages, final version, published in JHE
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