26 research outputs found
Obtaining the equation of motion for a fermionic particle in a generalized Lorentz-violating system framework
Using a generalized procedure for obtaining the dispersion relation and the
equation of motion for a propagating fermionic particle, we examine previous
claims for a preferred axis at (), embedded
in the framework of very special relativity (VSR). We show that, in a
relatively high energy scale, the corresponding equation of motion is reduced
to a conserving lepton number chiral equation previously predicted in the
literature. Otherwise, in a relatively low energy scale, the equation is
reduced to the usual Dirac equation for a free propagating fermionic particle.
It is accomplished by the suggestive analysis of some special cases where a
nonlinear modification of the action of the Lorentz group is generated by the
addition of a modified conformal transformation which, meanwhile, preserves the
structure of the ordinary Lorentz algebra in a very peculiar way. Some feasible
experiments, for which Lorentz violating effects here pointed out may be
detectable, are suggested.Comment: 10 page
New CP Violation in Neutrino Oscillations
Measurements of CP--violating observables in neutrino oscillation experiments
have been studied in the literature as a way to determine the CP--violating
phase in the mixing matrix for leptons. Here we show that such observables also
probe new neutrino interactions in the production or detection processes.
Genuine CP violation and fake CP violation due to matter effects are sensitive
to the imaginary and real parts of new couplings. The dependence of the CP
asymmetry on source--detector distance is different from the standard one and,
in particular, enhanced at short distances. We estimate that future neutrino
factories will be able to probe in this way new interactions that are up to
four orders of magnitude weaker than the weak interactions. We discuss the
possible implications for models of new physics.Comment: ReVTeX, 28 pages, 7 figues. v2: Modifications in section VIII to
reflect the fact that some of the couplings that were discussed in this
section are irrelevant to our analysis (as pointed out in hep-ph/0112329);
Added a discussion in section IX of the relevance of other future experiments
that will search for lepton flavor violatio
A general analysis with trilinear and bilinear R-parity violating couplings in the light of recent SNO data
We analyse an extension of the minimal supersymmetric standard model
including the dominant trilinear and bilinear R-parity violating contributions.
We take the trilinear terms from the superpotential and the bilinear terms from
the superpotential as well as the scalar potential. We compute the neutrino
masses induced by those couplings and determine the allowed ranges of the
R-parity violating parameters that are consistent with the latest SNO results,
atmospheric data and the Chooz constraint. We also estimate the effective mass
for neutrinoless double beta decay in such scenarios.Comment: 7 pages, Revtex, 1 PS figur
Reconstructing Seesaws
We explore some aspects of "reconstructing" the heavy singlet sector of
supersymmetric type I seesaw models, for two, three or four singlets. We work
in the limit where one light neutrino is massless. In an ideal world, where
selected coefficients of the TeV-scale effective Lagrangian could be measured
with arbitrary accuracy, the two-singlet case can be reconstructed, two three
or more singlets can be differentiated, and an inverse seesaw with four
singlets can be reconstructed. In a more realistic world, we estimate \ell_\a
\to \ell_\b \gamma expectations with a "Minimal-Flavour-Violation-like"
ansatz, which gives a relation between ratios of the three branching ratios.
The two singlet model predicts a discrete set of ratios.Comment: 14 page
Phenomenology of Maximal and Near-Maximal Lepton Mixing
We study the phenomenological consequences of maximal and near-maximal mixing
of the electron neutrino with other (=tau and/or muon) neutrinos. We
describe the deviations from maximal mixing in terms of a parameter
and quantify the present experimental
status for . We find that the global analysis of solar neutrino
data allows maximal mixing with confidence level better than 99% for
eV^2\lsim\Delta m^2\lsim2\times10^{-7} eV. In the mass ranges \Delta
m^2\gsim 1.5\times10^{-5} eV and eV^2\lsim\Delta
m^2\lsim2\times10^{-7} eV the full interval is allowed
within 4(99.995 % CL). We suggest ways to measure in future
experiments. The observable that is most sensitive to is the rate
[NC]/[CC] in combination with the Day-Night asymmetry in the SNO detector. With
theoretical and statistical uncertainties, the expected accuracy after 5 years
is . We also discuss the effects of maximal and
near-maximal -mixing in atmospheric neutrinos, supernova neutrinos, and
neutrinoless double beta decay.Comment: 49 pages Latex file using RevTeX. 16 postscript figures included. (
Fig.2 and Fig.4 bitmapped for compression,better resolution at
http://ific.uv.es/~pppac/). Improved presentation: some statements included
and labels added in figures. Some misprint corrected. Final version to appear
in Phys. Rev D. Report no: IFIC/00-40, IASSNS-HEP-00-5
More on deviation from bi-maximal neutrino mixing
We study the case of presenting the exact bi-maximal mixing form with
inducing the deviation from the bi-maximal mixing in the final form of
the Pontecorvo-Maki-Nakagawa-Sakata neutrino mixing, . We
will show that such possibility will lead to a democratic texture for the
charged lepton mass matrix and to a neutrino mass matrix with four null
entries.Comment: a scenario realizing our proposal is added, new references added, to
be published in J.Phys.
Effects of new physics in neutrino oscillations in matter
A new flavor changing electron neutrino interaction with matter would always
dominate the nu_e oscillation probability at sufficiently high neutrino
energies. Being suppressed by theta_{13}, the energy scale at which the new
effect starts to be relevant may be within the reach of realistic experiments,
where the peculiar dependence of the signal with energy could give rise to a
clear signature in the nu_e --> nu_tau channel. The latter could be observed by
means of a coarse large magnetized detector by exploiting tau --> mu decays. We
discuss the possibility of identifying or constraining such effects with a high
energy neutrino factory. We also comment on the model independent limits on
them.Comment: 11 pages, 5 figure
Suppressing the and neutrino masses by a superconformal force
The idea of Nelson and Strassler to obtain a power law suppression of
parameters by a superconformal force is applied to understand the smallness of
the parameter and neutrino masses in R-parity violating supersymmetric
standard models. We find that the low-energy sector should contain at least
another pair of Higgs doublets, and that a suppression of \lsim O(10^{-13})
for the parameter and neutrino masses can be achieved generically. The
superpotential of the low-energy sector happens to possess an anomaly-free
discrete R-symmetry, either or , which naturally suppresses certain
lepton-flavor violating processes, the neutrinoless double beta decays and also
the electron electric dipole moment. We expect that the escape energy of the
superconformal sector is \lsim O(10) TeV so that this sector will be
observable at LHC. Our models can accommodate to a large mixing among neutrinos
and give the same upper bound of the lightest Higgs mass as the minimal
supersymmetric standard model.Comment: 24 page
Testing neutrino mixing at future collider experiments
Low energy supersymmetry with bilinear breaking of R-parity leads to a
weak-scale seesaw mechanism for the atmospheric neutrino scale and a radiative
mechanism for the solar neutrino scale. The model has striking implications for
collider searches of supersymmetric particles. Assuming that the lightest SUSY
particle is the lightest neutralino we demonstrate that (i) The neutralino
decays inside the detector even for tiny neutrino masses. (ii) Measurements of
the neutrino mixing angles lead to predictions for the ratios of various
neutralino branching ratios implying an independent test of neutrino physics at
future colliders, such as the Large Hadron Collider or a Linear Collider.Comment: LaTex, 35 pages, 20 figures included, version 2, section on model
shortened, Fig. 13 replaced, typos corrected, version to appear in Phys.Rev.
Neutrinoless Double Beta Decay from Singlet Neutrinos in Extra Dimensions
We study the model-building conditions under which a sizeable
-decay signal to the recently reported level of~0.4 eV is due
to Kaluza--Klein singlet neutrinos in theories with large extra dimensions. Our
analysis is based on 5-dimensional singlet-neutrino models compactified on an
orbifold, where the Standard--Model fields are localized on a
3-brane. We show that a successful interpretation of a positive signal within
the above minimal 5-dimensional framework would require a non-vanishing shift
of the 3-brane from the orbifold fixed points by an amount smaller than the
typical scale (100 MeV) characterizing the Fermi nuclear momentum. The
resulting 5-dimensional models predict a sizeable effective Majorana-neutrino
mass that could be several orders of magnitude larger than the light neutrino
masses. Most interestingly, the brane-shifted models with only one bulk sterile
neutrino also predict novel trigonometric textures leading to mass scenarios
with hierarchical active neutrinos and large - and
- mixings that can fully explain the current atmospheric and
solar neutrino data.Comment: 33 pages, LaTeX, minor rewordings, references adde