747 research outputs found
The golden ratio prediction for the solar neutrino mixing
We present a simple texture that predicts the cotangent of the solar neutrino
mixing angle to be equal to the golden ratio. This prediction is 1.4 standard
deviations below the present best-fit value and final SNO and KamLAND data
could discriminate it from tri-bi-maximal mixing. The neutrino mass matrix is
invariant under a Z_2 x Z'_2 symmetry: that geometrically is a reflection along
the diagonal of the golden rectangle. Assuming an analogous structure in the
quark sector suggests a golden prediction for the Cabibbo angle, theta_C =
pi/4- theta_12 = 13.3 degree, up to uncertainties comparable to V_{ub}.Comment: 5 pages. Final version, to appear on PR
Gauged Discrete Symmetries and Proton Stability
We discuss the results of a search for anomaly free Abelian Z_N discrete
symmetries that lead to automatic R-parity conservation and prevents dangerous
higher-dimensional proton decay operators in simple extensions of the minimal
supersymmetric extension of the standard model (MSSM) based on the left-right
symmetric group, the Pati-Salam group and SO(10). We require that the
superpotential for the models have enough structures to be able to give correct
symmetry breaking to MSSM and potentially realistic fermion masses. We find
viable models in each of the extensions and for all the cases, anomaly freedom
of the discrete symmetry restricts the number of generations.Comment: 8 pages, 2 figures; v2 : typos fixed, references adde
R-Parity Violation and Non-Abelian Discrete Family Symmetry
We investigate the implications of R-parity violating operators in a model
with family symmetry. The family symmetry can determine the form of R-parity
violating operators as well as the Yukawa matrices responsible for fermion
masses and mixings. In this paper we consider a concrete model with non-abelian
discrete symmetry Q_6 which contains only three R-parity violating operators.
We find that ratios of decay rates of the lepton flavor violating processes are
fixed thanks to the family symmetry, predicting BR(tau to 3e)/BR(tau to 3mu) ~
4 m_{mu}^2/m_{tau}^2.Comment: 20 pages, 3 figure
Bilinear R-parity violation with flavor symmetry
Bilinear R-parity violation (BRPV) provides the simplest intrinsically
supersymmetric neutrino mass generation scheme. While neutrino mixing
parameters can be probed in high energy accelerators, they are unfortunately
not predicted by the theory. Here we propose a model based on the discrete
flavor symmetry with a single R-parity violating parameter, leading to
(i) correct Cabbibo mixing given by the Gatto-Sartori-Tonin formula, and a
successful unification-like b-tau mass relation, and (ii) a correlation between
the lepton mixing angles and in agreement with
recent neutrino oscillation data, as well as a (nearly) massless neutrino,
leading to absence of neutrinoless double beta decay.Comment: 16 pages, 3 figures. Extended version, as published in JHE
Direct and Indirect Detection of Dark Matter in D6 Flavor Symmetric Model
We study a fermionic dark matter in a non-supersymmetric extension of the
standard model with a family symmetry based on D6xZ2xZ2. In our model, the
final state of the dark matter annihilation is determined to be e+ e- by the
flavor symmetry, which is consistent with the PAMELA result. At first, we show
that our dark matter mass should be within the range of 230 GeV - 750 GeV in
the WMAP analysis combined with mu to e gamma constraint. Moreover we
simultaneously explain the experiments of direct and indirect detection, by
simply adding a gauge and D6 singlet real scalar field. In the direct detection
experiments, we show that the lighter dark matter mass ~ 230 GeV and the
lighter standard model Higgs boson ~ 115 GeV is in favor of the observed bounds
reported by CDMS II and XENON100. In the indirect detection experiments, we
explain the positron excess reported by PAMELA through the Breit-Wigner
enhancement mechanism. We also show that our model is consistent with no
antiproton excess suggested by PAMELA.Comment: 20 pages, 9 figures, 2 tables, accepted version for publication in
European Physical Journal
Validation of standard and alternative satellite ocean-color chlorophyll products off Western Iberia
Chlorophyll a concentration (Chl) product validation off theWestern Iberian coast is here undertaken by directly
comparing remote sensing data with in situ surface reference values. Both standard and recently developed
alternative algorithms are considered for match-up data analysis. The investigated standard products are those
produced by the MERIS (algal 1 and algal 2) and MODIS (OC3M) algorithms. The alternative data products include
those generatedwithin the CoastColour Project and Ocean Color Climate Change Initiative (OC-CCI) funded
by ESA, as well as a neural net model trained with field measurements collected in the Atlantic off Portugal
(MLPATLP). Statistical analyses showed that satellite Chl estimates tend to be larger than in situ reference values.
The study also revealed that a non-uniform Chl distribution in the water column can be a concurring factor to the
documented overestimation tendency when considering larger optical depth match-up stations. Among standard
remote sensing products, MODIS OC3M and MERIS algal 2 yield the best agreement with in situ data. The
performance of MLPATLP highlights the capability of regional solutions to further improve Chl retrieval by accounting
for environmental specificities. Results also demonstrate the relevance of oceanographic regions such
as the Nazaré area to evaluate how complex hydrodynamic conditions can influence the quality of Chl products.This studywas performed in the framework
of HabSpot FCT Project, PTDC/MAR/100348/2008 and European
Space Agency projects DUE CoastColour (ESRIN/AO/1-6141/09/l-EC)
and Climate Change Iniciative — Ocean Color (AO-1/6207/09/I-LG).
The work has been also partially supported by the European Space
Agency within the framework of the MERIS Validation Activities under
contract n. 12595/09/I-OL, and sampling activities benefited from
European projects HERMES (GOCE-CT-2005-511234) and Hermione
(EC contract 226354) support. We would like to thank NASA OBPG for
the MODIS data and ESA Project AOPT-2423 for providing MERIS full
resolution images. Ana C. Brito was funded
by a Portuguese Post-doc grant from FCT (BPD/63017/2009) and by the
Investigador FCT Program (IF/00331/2013). Davide D'Alimonte was
funded by Investigador FCT Program (IF/00541/2013).info:eu-repo/semantics/publishedVersio
Search for Dark Matter WIMPs using Upward Through-going Muons in Super-Kamiokande
We present the results of indirect searches for Weakly Interacting Massive
Particles (WIMPs) with 1679.6 live days of data from the Super-Kamiokande
detector using neutrino-induced upward through-going muons. The search is
performed by looking for an excess of high energy muon neutrinos from WIMP
annihilations in the Sun, the core of the Earth, and the Galactic Center, as
compared to the number expected from the atmospheric neutrino background. No
statistically significant excess was seen. We calculate flux limits in various
angular cones around each of the above celestial objects. We obtain
conservative model-independent upper limits on WIMP-nucleon cross-section as a
function of WIMP mass and compare these results with the corresponding results
from direct dark matter detection experiments.Comment: 10 pages, 14 figures, Submitted to Phys. Rev.
Softening the Supersymmetric Flavor Problem in Orbifold GUTs
The infra-red attractive force of the bulk gauge interactions is applied to
soften the supersymmetric flavor problem in the orbifold SU(5) GUT of Kawamura.
Then this force aligns in the infra-red regime the soft supersymmetry breaking
terms out of their anarchical disorder at a fundamental scale, in such a way
that flavor-changing neutral currents as well as dangerous CP-violating phases
are suppressed at low energies. It is found that this dynamical alignment is
sufficiently good compared with the current experimental bounds, as long as the
diagonalization matrices of the Yukawa couplings are CKM-like.Comment: 15 pages,4 figure
Limit On the Neutrino Magnetic Moment Using 1496 Days of Super-Kamiokande-i Solar Neutrino Data
A search for a non-zero neutrino magnetic moment has been conducted using
1496 live days of solar neutrino data from {\SK}. Specifically, we searched for
distortions to the energy spectrum of recoil electrons arising from magnetic
scattering due to a non-zero neutrino magnetic moment. In the absence of clear
signal, we found at 90% C.L. by
fitting to the Super-Kamiokande day/night spectra. The fitting took into
account the effect of neutrino oscillation on the shapes of energy spectra.
With additional information from other solar neutrino and KamLAND experiments
constraining the oscillation region, a limit of at 90% C.L. was obtained.Comment: 5 pages, 4 figure
The Golden Ratio Prediction for the Solar Angle from a Natural Model with A5 Flavour Symmetry
We formulate a consistent model predicting, in the leading order
approximation, maximal atmospheric mixing angle, vanishing reactor angle and
tan {\theta}_12 = 1/{\phi} where {\phi} is the Golden Ratio. The model is based
on the flavour symmetry A5 \times Z5 \times Z3, spontaneously broken by a set
of flavon fields. By minimizing the scalar potential of the theory up to the
next-to-leading order in the symmetry breaking parameter, we demonstrate that
this mixing pattern is naturally achieved in a finite portion of the parameter
space, through the vacuum alignment of the flavon fields. The leading order
approximation is stable against higher-order corrections. We also compare our
construction to other models based on discrete symmetry groups.Comment: 28 pages, 2 figures. Minor changes, references added. Corrected typos
in Appendix A. Version appeared on JHE
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