1,263 research outputs found
Are there sterile neutrinos at the eV scale?
New predictions for the anti-neutrino flux emitted by nuclear reactors
suggest that reactor experiments may have measured a deficit in the
anti-neutrino flux, which can be interpreted in terms of oscillations between
the known active neutrinos and new sterile states. Motivated by this
observation, we perform a re-analysis of global short-baseline neutrino
oscillation data in a framework with one or two sterile neutrinos. While one
sterile neutrino is still not sufficient to reconcile the signals suggested by
reactor experiments and by the LSND and MiniBooNE experiments with null results
from other searches, we find that, with the new reactor flux prediction, the
global fit improves considerably when the existence of two sterile neutrinos is
assumed.Comment: 5 pages, 5 figures, v2: reference and acknowledgements adde
A SUSY A4 model for fermion masses and mixings
We study a supersymmetric extension of the Standard Model based on discrete
A4xZ3xZ4 flavor symmetry. We obtain quark mixing angles as well as a realistic
fermion mass spectrum and we predict tribimaximal leptonic mixing by a
spontaneous breaking of A4. The top quark Yukawa interaction is present at the
renormalizable level in the superpotential while all the other Yukawa
interactions arise only at higher orders. We study the Higgs potential and show
that it can potentially solve the so called vacuum alignment problem. The
leading order predictions are not spoiled by subleading corrections.Comment: version accepted in JHEP, Z3xZ2 changed in Z3xZ4, typos in table
corrected, references adde
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
LFV and Dipole Moments in Models with A4 Flavour Symmetry
It is presented an analysis on lepton flavour violating transitions, leptonic
magnetic dipole moments and electric dipole moments in a class of models
characterized by the flavour symmetry A4 x Z3 x U(1)_FN, whose choice is
motivated by the approximate Tri-Bimaximal mixing observed in neutrino
oscillations. A low-energy effective Lagrangian is constructed, where these
effects are dominated by dimension six operators, suppressed by the scale M of
new physics. All the flavour breaking effects are universally described by the
vacuum expectation values of a set of spurions. Two separate cases, a
supersymmetric and a general one, are described. An upper limit on the reactor
angle of a few percent is concluded.Comment: 10 pages, 1 figure. Adapted from a talk given at "DISCRETE'08:
Symposium on Prospects in the Physics of Discrete Symmetries", December 11-16
2008, Valencia, Spai
Sterile neutrino decay and the LSND experiment
We propose a new explanation of the intriguing LSND evidence for electron
antineutrino appearance in terms of heavy (mostly sterile) neutrino decay via a
coupling with a light scalar and light (mostly active) neutrinos. We perform a
fit to the LSND data, as well as all relevant null-result experiments, taking
into account the distortion of the spectrum due to decay. By requiring a
coupling g ~ 10^{-5}, a heavy neutrino mass m_4 ~ 100 keV and a mixing with
muon neutrinos |U_{mu 4}|^2 ~ 10^{-2}, we show that this model explains all
existing data evading constraints that disfavor standard (3+1) neutrino models.Comment: 3pp. Talk given at 9th International Conference on Astroparticle and
Underground Physics (TAUP 2005), Zaragoza, Spain, 10-14 Sep 200
Strategies to Mitigate Seasonality of Production in Grassland-Based Systems
Key points
1. Fertilisation use and manipulation can cost-effectively alter species composition, increase seasonal herbage production and improve herbage quality.
2. Choice of suitable grassland species, varieties and mixtures offers opportunity to mitigate limitations of seasonal grassland production.
3. Special purpose fodder crops, cereals, shrubs and trees offer alternative or supplementary feed sources.
4. Manipulation of stocking rates, grazing systems, transhumance and pasture management at various times of the season are significant advantageous options.
5. Integration of different strategies is essential to mitigate seasonality in systems of animal production that must be inherently more sustainable over a longer time frame
Strategies to Mitigate Seasonality of Production in Grassland-Based Systems
Fertilisation use and manipulation can cost-effectively alter species composition, increase seasonal herbage production and improve herbage quality. Choice of suitable grassland species, varieties and mixtures offers opportunity to mitigate limitations of seasonal grassland production. Special purpose fodder crops, cereals, shrubs and trees offer alternative or supplementary feed sources. Manipulation of stocking rates, grazing systems, transhumance and pasture management at various times of the season are significant advantageous options. Integration of different strategies is essential to mitigate seasonality in systems of animal production that must be inherently more sustainable over a longer time frame
Discrete Flavor Symmetries and Models of Neutrino Mixing
We review the application of non abelian discrete groups to the theory of
neutrino masses and mixing, which is strongly suggested by the agreement of the
Tri-Bimaximal mixing pattern with experiment. After summarizing the motivation
and the formalism, we discuss specific models, based on A4, S4 and other finite
groups, and their phenomenological implications, including lepton flavor
violating processes, leptogenesis and the extension to quarks. In alternative
to Tri-Bimaximal mixing the application of discrete flavor symmetries to
quark-lepton complementarity and Bimaximal Mixing is also considered.Comment: 54 pages, 3 figures, minor changes in the text and references adde
New interactions: past and future experiments
In this talk I will review the present status and future perspectives of some
popular extensions of the conventional three-neutrino oscillation scenario,
from a purely phenomenological point of view. For concreteness I will focus
only on three specific scenarios: non-standard neutrino interactions with
matters, models with extra sterile neutrinos, and neutrino decay and
decoherence.Comment: LaTeX file using jpconf class, 8 pages, 2 tables. Proceedings of the
"XXIII International Conference on Neutrino Physics and Astrophysics"
(Neutrino 08), Christchurch, New Zealand, May 25-31, 200
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