Simple description of neutrinos in SU(5)

We show that experimental results for the masses and mixing of the neutrinos can be understood naturally by a simple grand unification model of SU(5) coupled to N=1 supergravity. No right-handed neutrinos are included. The left-handed neutrinos receive Majorana masses through the couplings with a Higgs boson of symmetric $\bf 15$ representation. Introducing $\bar{\bf 45}$ representation is optional for describing the masses of down-type quarks and charged leptons.Comment: 10 page

Four species neutrino oscillations at ν\nu-Factory: sensitivity and CP-violation

The prospects of measuring the leptonic angles and CP-odd phases at a {\em neutrino factory} are discussed in the scenario of three active plus one sterile neutrino. We consider the \nu_\mu \raw \nu_e LSND signal. Its associated large mass difference leads to observable neutrino oscillations at short ($\sim 1$ km) baseline experiments. Sensitivities to the leptonic angles down to $10^{-3}$ can be easily achieved with a 1 Ton detector. Longer baseline experiments ($\sim 100$ km) with a 1 Kton detector can provide very clean tests of CP-violation especially through tau lepton detection.Comment: 15 pages, LaTeX2e, 14 eps files, use package epsfi

Role of lepton flavor violating (LFV) muon decay in Seesaw model and LSND

The aim of the work is to study LFV in a newly proposed Seesaw model of neutrino mass and to see whether it could explain LSND excess. The motivation of this Seesaw model was that there was no new physics beyond the TeV scale. By studying \mu \to 3e in this model, it is shown that the upper bound on the branching ratio requires Higgs mass m_{h} of a new scalar doublet with lepton number L=-1 needed in the model has to be about 9 TeV. The predicted branching ratio for \mu \to e\nu_{l}\bar{\nu}_{l} is too small to explain the LSND. PACS: 11.30.Hv, 14.60.PqComment: 05 pages, three figures, the version to appear in PR

Classification of Effective Neutrino Mass Operators

We present a classification of SU(3) x SU(2) x U(1) gauge invariant \Delta L = 2 (L being lepton number) effective operators relevant for generating small Majorana neutrino masses. Operators of dimension up to 11 have been included in our analysis. This approach enables us to systematically identify interesting neutrino mass models. It is shown that many of the well-known models fall into this classification. In addition, a number of new models are proposed and their neutrino phenomenology is outlined. Of particular interest is a large class of models in which neutrinoless double beta decays arise at a lower order compared to the neutrino mass, making these decays accessible to the current round of experiments.Comment: 34 pages in RevTeX with 18 figure

Genotype imputation for the prediction of genomic breeding values in non-genotyped and low-density genotyped individuals

<p>Abstract</p> <p>Background</p> <p>There is wide interest in calculating genomic breeding values (GEBVs) in livestock using dense, genome-wide SNP data. The general framework for genomic selection assumes all individuals are genotyped at high-density, which may not be true in practice. Methods to add additional genotypes for individuals not genotyped at high density have the potential to increase GEBV accuracy with little or no additional cost. In this study a long haplotype library was created using a long range phasing algorithm and used in combination with segregation analysis to impute dense genotypes for non-genotyped dams in the training dataset (S1) and for non-genotyped or low-density genotyped individuals in the prediction dataset (S2), using the 14^th QTL-MAS Workshop dataset. Alternative low-density scenarios were evaluated for accuracy of imputed genotypes and prediction of GEBVs.</p> <p>Results</p> <p>In S1, females in the training population were not genotyped and prediction individuals were either not genotyped or genotyped at low-density (evenly spaced at 2, 5 or 10 Mb). The proportion of correctly imputed genotypes for training females did not change when genotypes were added for individuals in the prediction set whereas the number of correctly imputed genotypes in the prediction set increased slightly (S1). The S2 scenario assumed the complete training set was genotyped for all SNPs and the prediction set was not genotyped or genotyped at low-density. The number of correctly imputed genotypes increased with genotyping density in the prediction set. Accuracy of genomic breeding values for the prediction set in each scenario were the correlation of GEBVs with true breeding values and were used to evaluate the potential loss in accuracy with reduced genotyping. For both S1 and S2 the GEBV accuracies were similar when the prediction set was not genotyped and increased with the addition of low-density genotypes, with the increase larger for S2 than S1.</p> <p>Conclusions</p> <p>Genotype imputation using a long haplotype library and segregation analysis is promising for application in sparsely-genotyped pedigrees. The results of this study suggest that dense genotypes can be imputed for selection candidates with some loss in genomic breeding value accuracy, but with levels of accuracy higher than traditional BLUP estimated breeding values. Accurate genotype imputation would allow for a single low-density SNP panel to be used across traits.</p

Constraining dynamical dark energy with a divergence-free parametrization in the presence of spatial curvature and massive neutrinos

In this paper, we report the results of constraining the dynamical dark energy with a divergence-free parameterization, $w(z) = w_{0} + w_{a}(\frac{\ln(2+z)}{1+z}-\ln2)$, in the presence of spatial curvature and massive neutrinos, with the 7-yr WMAP temperature and polarization data, the power spectrum of LRGs derived from SDSS DR7, the Type Ia supernova data from Union2 sample, and the new measurements of $H_0$ from HST, by using a MCMC global fit method. Our focus is on the determinations of the spatial curvature, $\Omega_k$, and the total mass of neutrinos, $\sum m_{\nu}$, in such a dynamical dark energy scenario, and the influence of these factors to the constraints on the dark energy parameters, $w_0$ and $w_a$. We show that $\Omega_k$ and $\sum m_{\nu}$ can be well constrained in this model; the 95% CL limits are: $-0.0153<\Omega_k<0.0167$ and $\sum m_{\nu}<0.56$ eV. Comparing to the case in a flat universe, we find that the error in $w_0$ is amplified by 25.51%, and the error in $w_a$ is amplified by 0.14%; comparing to the case with a zero neutrino mass, we find that the error in $w_0$ is amplified by 12.24%, and the error in $w_a$ is amplified by 1.63%.Comment: 5 pages, 2 figures; discussions added; accepted for publication in Physics Letters

Sterile Neutrino as a Bulk Neutrino

If light sterile neutrinos are needed to understand the neutrino puzzles, as is currently indicated, a major theoretical challenge is to understand why its mass is so small. It is a more serious problem than understanding the small mass of the familiar neutrinos. We discuss a new way to solve this problem by identifying the sterile neutrino as gauge neutral fermion propagating in the bulk of a higher dimensional theory, with bulk size of order of a millimeter. The smallness of its mass is then a consequence of the size of the extra dimension and does not need the introduction of new symmetries. We present a realistic model for neutrino masses and mixings that implements this idea.Comment: 13 pages, no figures; minor typos correcte

L_e + L_\mu - L_\tau - L_s Symmetry and a Mixed 2+2 Scenario for Neutrino Oscillations

Recent results from SuperKamiokande and SNO experiments have set severe constraints on possible mixings of a light sterile neutrino, \nu_s, with the three active species required for a simultaneous explanation of the solar, atmospheric and LSND neutrino oscillation data. A consistent scheme has emerged from a global analysis of the data wherein two of the neutrinos are nearly degenerate with a mass of order 1 eV, that mix significantly with the two lighter states. We present realizations of such a mixed 2+2 oscillation scenario based on L_e + L_\mu - L_\tau - L_s symmetry (L_i stands for the ith lepton number). Breaking of of this lepton number symmetry by a small mass term for \nu_s leads to the required large mixings for both the atmospheric and the solar neutrino oscillations. Sum rules for the neutrino oscillation parameters are derived within this scheme, and are shown to be consistent with present data. These models predict U_{e3} = 0.02-0.03, which can serve as a test of this idea. We also present gauge models based on mirror extensions of the Standard Model that naturally lead to a light sterile neutrino with the required mixing pattern.Comment: 13 pages, RevTe

Neutrino Oscillations in the Framework of Three-Generation Mixings with Mass Hierarchy

We have analyzed the results of reactor and accelerator neutrino oscillation experiments in the framework of a general model with mixing of three neutrino fields and a neutrino mass hierarchy that can accommodate the results of the solar neutrino experiments. It is shown that $\nu_\mu \leftrightarrows \nu_e$ oscillations with $0.6 \le \Delta m^2 \le 100 \, \mathrm{eV}^2$ and amplitude larger than $2 \times 10^{-3}$ are not compatible with the existing limits on neutrino oscillations if the non-diagonal elements of the mixing matrix $\left| U_{e3} \right|$ and $\left| U_{\mu3} \right|$ are small. Thus, if the excess of electron events recently observed in the LSND experiment is due to $\nu_\mu \leftrightarrows \nu_e$ oscillations, the mixing in the lepton sector is basically different from the CKM mixing of quarks. If this type of mixing is realized in nature, the observation of $\nu_\mu \leftrightarrows \nu_e$ oscillations would not influence $\nu_\mu \leftrightarrows \nu_\tau$ oscillations that are being searched for in the CHORUS and NOMAD experiments.Comment: Revtex file, 13 pages + 2 figures (included). The postscript file of text and figures is available at http://www.to.infn.it/teorici/giunti/papers.html or ftp://ftp.to.infn.it/pub/giunti/1995/dftt-25-95/dftt-25-95.ps.

Sterile Neutrinos in E_6 and a Natural Understanding of Vacuum Oscillation Solution to the Solar Neutrino Puzzle

If Nature has chosen the vacuum oscillation solution to the Solar neutrino puzzle, a key theoretical challenge is to understand the extreme smallness of the $\Delta m^2_{\nu_e-\nu_X}$ ($\sim 10^{-10} eV^2$) required for the purpose. We find that in a class of models such as [SU(3)]^3 or its parent group E_6, which contain one sterile neutrino, $\nu_{is}$ for each family, the $\Delta m^2_{\nu_i-\nu_{is}}$ is proportional to the cube of the lepton Yukawa coupling. Therefore fitting the atmospheric neutrino data then predicts the $\nu_e-\nu_{es}$ mass difference square to be $\sim (\frac{m_e}{m_{\mu}})^3 \Delta m^2_{atmos}$, where the atmospheric neutrino data is assumed to be solved via the $\nu_{\mu}-\nu_{\mu s}$ oscillation. This provides a natural explanation of the vacuum oscillation solution to the solar neutrino problem.Comment: 7 pages, UMD-PP-99-109; new references added; no other chang