836 research outputs found
Minimal archi-texture for neutrino mass matrices
The origin of the observed masses and mixing angles of quarks and leptons is
one of imperative subjects in and beyond the standard model. Toward a deeper
understanding of flavor structure, we investigate in this paper the minimality
of fermion mass (Yukawa) matrices in unified theory. That is, the simplest
matrix form is explored in light of the current experimental data for quarks
and leptons, including the recent measurements of quark CP violation and
neutrino oscillations. Two types of neutrino mass schemes are particularly
analyzed; (i) Majorana masses of left-handed neutrinos with unspecified
mechanism and (ii) Dirac and Majorana masses introducing three right-handed
neutrinos. As a result, new classes of neutrino mass matrices are found to be
consistent to the low-energy experimental data and high-energy unification
hypothesis. For distinctive phenomenological implications of the minimal
fermion mass textures, we discuss flavor-violating decay of charged leptons,
the baryon asymmetry of the universe via thermal leptogenesis, neutrino-less
double beta decay, and low-energy leptonic CP violation.Comment: 37 pages, 6 figure
Neutrino mixing and CP violation from Dirac-Majorana bimaximal mixture and quark-lepton unification
We demonstrate that only two ansatz can produce the features of the neutrino
mixing angles. The first ansatz comes from the quark-lepton grand unification;
is satisfied for left-handed neutrinos, where
are the Dirac mass eigenstates and are the flavour
eigenstates. The second ansatz comes from the assumption; is satisfied between the Dirac mass eigenstates
and the light Majorana neutrino mass eigenstates , where
is the bimaximal mixing matrix. By these two ansatz, the
Maki-Nakagawa-Sakata matrix is given by . We find that in this model the novel relation is satisfied, where and are
solar and CHOOZ angle respectively. This "Solar-CHOOZ Complementarity" relation
indicates that only if the CHOOZ angle is sizable, the solar
angle can deviate from the maximal mixing. We also infer the CP
violation in neutrino oscillations. The leptonic Dirac CP phase
is predicted as , where are the CKM parameters in Wolfenstein parametrization. Furthermore, we
remark that the ratio of the Jarlskog CP violation factor for quarks and
leptons is important, because the large uncertainty on is cancelled out
in the ratio, .Comment: 9 pages, no figures; v2 references added, v3 references adde
Precise measurement of the solar neutrino day-night and seasonal variation in Super-Kamiokande-I
Global fits to neutrino oscillation data
I summarize the determination of neutrino oscillation parameters within the
three-flavor framework from world neutrino oscillation data with date of May
2006, including the first results from the MINOS long-baseline experiment. It
is illustrated how the determination of the leading "solar" and "atmospheric"
parameters, as well as the bound on emerge from an interplay of
various complementary data sets. Furthermore, I discuss possible implications
of sub-leading three-flavor effects in present atmospheric neutrino data
induced by and for the bound on
and non-maximal values of , emphasizing, however, that these
effects are not statistically significant at present. Finally, in view of the
upcoming MiniBooNE results I briefly comment on the problem to reconcile the
LSND signal.Comment: 5 pages, 5 figures, talk presented at the SNOW2006 workshop,
Stockholm, 2-6 May 200
Quantum Isometries of the finite noncommutative geometry of the Standard Model
We compute the quantum isometry group of the finite noncommutative geometry F
describing the internal degrees of freedom in the Standard Model of particle
physics. We show that this provides genuine quantum symmetries of the spectral
triple corresponding to M x F where M is a compact spin manifold. We also prove
that the bosonic and fermionic part of the spectral action are preserved by
these symmetries.Comment: 29 pages, no figures v3: minor change
Neutrino signals from electroweak bremsstrahlung in solar WIMP annihilation
Bremsstrahlung of and gauge bosons, or photons, can be an important
dark matter annihilation channel. In many popular models in which the
annihilation to a pair of light fermions is helicity suppressed, these
bremsstrahlung processes can lift the suppression and thus become the dominant
annihilation channels. The resulting dark matter annihilation products contain
a large, energetic, neutrino component. We consider solar WIMP annihilation in
the case where electroweak bremsstrahlung dominates, and calculate the
resulting neutrino spectra. The flux consists of primary neutrinos produced in
processes such as and , and secondary neutrinos produced via the decays of gauge
bosons and charged leptons. After dealing with the neutrino propagation and
flavour evolution in the Sun, we consider the prospects for detection in
neutrino experiments on Earth. By comparing our signal with that for
annihilation to , we show that the detection prospects for the
bremsstrahlung annihilation channel are favourable.Comment: 18 pages, 5 figures. Discussion expanded; matches published versio
Exploration of Possible Quantum Gravity Effects with Neutrinos II: Lorentz Violation in Neutrino Propagation
It has been suggested that the interactions of energetic particles with the
foamy structure of space-time thought to be generated by quantum-gravitational
(QG) effects might violate Lorentz invariance, so that they do not propagate at
a universal speed of light. We consider the limits that may be set on a linear
or quadratic violation of Lorentz invariance in the propagation of energetic
neutrinos, v/c=[1 +- (E/M_\nuQG1)] or [1 +- (E/M_\nu QG2}^2], using data from
supernova explosions and the OPERA long-baseline neutrino experiment.Comment: 8 pages, 6 figures, proceedings for invited talk by A.Sakharov at
DISCRETE'08, Valencia, Spain; December 200
Neutrino Physics at the Turn of the Millenium
Recent solar & atmospheric nu-data strongly indicate need for physics beyond
the Standard Model. I review the ways of reconciling them in terms of 3-nu
oscillations. Though not implied by data, bi-maximal nu-mixing models emerge as
a possibility. SUSY with broken R-parity provides an attractive way to
incorporate it, opening the possibility of testing nu-anomalies at high- energy
colliders such as the LHC or at the upcoming long-baseline or nu- factory
experiments. Reconciling, in addition, the LSND hint requires a fourth, light
sterile neutrino, nus. The simplest are the most symmetric scenarios, in which
2 of the 4 neutrinos are maximally-mixed and lie at the LSND scale, while the
others are at the solar scale. The lightness of nus, the nearly maximal
atmospheric mixing, and the solar/atmospheric splittings all follow naturally
from the assumed lepton-number symmetry and its breaking. These basic schemes
can be distinguished at neutral-current-sensitive solar & atmospheric neutrino
experiments such as SNO. However underground experiments have not yet proven
neutrino masses, as there are many alternatives. For example flavour changing
interactions can play an important role in the explanation of solar and
contained atmospheric data and could be tested e.g through \mu \to e + \gamma,
\mu-e conversion in nuclei, unaccompanied by neutrino-less double beta decay.
Conversely, a short-lived numu might play a role in the explanation of the
atmospheric data. Finally, in the presence of a nus, a long-lived heavy nutau
could delay the time at which the matter and radiation contributions to the
energy density of the Universe become equal, reducing density fluctuations on
smaller scales, thus saving the standard CDM scenario, while the light nue,
numu and nus would explain the solar & atmospheric data.Comment: Invited talk at 2nd International Conference on Non-Accelerator New
Physics (NANP-99), Dubna, June 28 - July 3, 199
Scalar Bilepton Dark Matter
In this work we show that 3-3-1 model with right-handed neutrinos has a
natural weakly interacting massive particle (WIMP) dark mater candidate. It is
a complex scalar with mass of order of some hundreds of GeV which carries two
units of lepton number, a scalar bilepton. This makes it a very peculiar WIMP,
very distinct from Supersymmetric or Extra-dimension candidates. Besides,
although we have to make some reasonable assumptions concerning the several
parameters in the model, no fine tunning is required in order to get the
correct dark matter abundance. We also analyze the prospects for WIMP direct
detection by considering recent and projected sensitivities for WIMP-nucleon
elastic cross section from CDMS and XENON Collaborations.Comment: 21 pages, 8 figures, uses iopart.cls, same text as published version
with a small different arrangement of figure
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