Lifting a Realistic SO(10) Grand Unified Model to Five Dimensions

It has been shown recently that the problem of rapid proton decay induced by dimension five operators arising from the exchange of colored Higgsinos can be simply avoided in grand unified models where a fifth spatial dimension is compactified on an orbifold. Here we demonstrate that this idea can be used to solve the Higgsino-mediated proton decay problem in any realistic SO(10) model by lifting that model to five dimensions. A particular SO(10) model that has been proposed to explain the pattern of quark and lepton masses and mixings is used as an example. The idea is to break the SO(10) down to the Pati-Salam symmetry by the orbifold boundary conditions. The entire four-dimensional SO(10) model is placed on the physical SO(10) brane except for the gauge fields, the 45 and a single 10 of Higgs fields, which are placed in the five-dimensional bulk. The structure of the Higgs superpotential can be somewhat simplified in doing so, while the Yukawa superpotential and mass matrices derived from it remain essentially unaltered.Comment: 17 pages, version to be published in Phys. Rev. D with expanded discussion of the suppression of dim-5 proton decay operator

Explicit SO(10) Supersymmetric Grand Unified Model for the Higgs and Yukawa Sectors

A complete set of fermion and Higgs superfields is introduced with well-defined SO(10) properties and U(1) x Z_2 x Z_2 family charges from which the Higgs and Yukawa superpotentials are constructed. The structures derived for the four Dirac fermion and right-handed Majorana neutrino mass matrices coincide with those previously obtained from an effective operator approach. Ten mass matrix input parameters accurately yield the twenty masses and mixings of the quarks and leptons with the bimaximal atmospheric and solar neutrino vacuum solutions favored in this simplest version.Comment: Published version appearing in PRL in which small modifications to original submission and a paragraph concerning proton decay appea

Leptogenesis in the type III seesaw mechanism

It is shown that the type III seesaw mechanism proposed recently can have certain advantages over the conventional (or type I) seesaw mechanism for leptogenesis. In particular a resonant enhancement of leptogenesis via heavy quasi-Dirac right-handed neutrino pairs can occur without a special flavor form or "texture" of the mass matrices being assumed. Some of the requirements for neutrino mixing and leptogenesis are effectively decoupled.Comment: 12 pages including one figure, several references adde

Resonant leptogenesis in a predictive SO(10) grand unified model

An SO(10) grand unified model considered previously by the authors featuring lopsided down quark and charged lepton mass matrices is successfully predictive and requires that the lightest two right-handed Majorana neutrinons be nearly degenerate in order to obtain the LMA solar neutrino solution. Here we use this model to test its predictions for baryogenesis through resonant-enhanced leptogenesis. With the conventional type I seesaw mechanism, the best predictions for baryogenesis appear to fall a factor of three short of the observed value. However, with a proposed type III seesaw mechanism leading to three pairs of massive pseudo-Dirac neutrinos, resonant leptogenesis is decoupled from the neutrino mass and mixing issues with successful baryogenesis easily obtained.Comment: 22 pages including 1 figure; published version with reference adde

Realization of the Large Mixing Angle Solar Neutrino Solution in an SO(10) Supersymmetric Grand Unified Model

An SO(10) supersymmetric grand unified model proposed earlier leading to the solar solution involving ``just-so'' vacuum oscillations is reexamined to study its ability to obtain the other possible solar solutions. It is found that all four viable solar neutrino oscillation solutions can be achieved in the model simply by modification of the right-handed Majorana neutrino mass matrix, M_R. Whereas the small mixing and vacuum solutions are easily obtained with several texture zeros in M_R, the currently-favored large mixing angle solution requires a nearly geometric hierarchical form for M_R that leads by the seesaw formula to a light neutrino mass matrix which has two or three texture zeros. The form of the matrix which provides the ``fine-tuning'' necessary to achieve the large mixing angle solution can be understood in terms of Froggatt-Nielsen diagrams for the Dirac and right-handed Majorana neutrino mass matrices. The solution fulfils several leptogenesis requirements which in turn can be responsible for the baryon asymmetry in the universe.Comment: 14 pages including 2 figure

Lepton Flavor Violation in Supersymmetric SO(10) Grand Unified Models

The study for lepton flavor violation combined with the neutrino oscillation may provide more information about the lepton flavor structure of the grand unified theory. In this paper, we study two lepton flavor violation processes, $\tau\to \mu\gamma$ and $Z\to \tau\mu$, in the context of supersymmetric SO(10) grand unified models. We find the two processes are both of phenomenological interest. In particular the latter may be important in some supersymmetric parameter space where the former is suppressed. Thus, Z-dacay may offer another chance for looking for lepton flavor violation.Comment: 26 pages, 10 figure

Symmetric Textures in SO(10) and LMA Solution for Solar Neutrinos

We analyze a model based on SUSY SO(10) combined with SU(2) family symmetry and symmetric mass matrices constructed by the authors recently. Previously, only the parameter space for the LOW and vacuum oscillation (VO) solutions was investigated. We indicate in this note the parameter space which leads to large mixing angle (LMA) solution to the solar neutrino problem with a slightly modified effective neutrino mass matrix. The symmetric mass textures arising from the left-right symmetry breaking and the SU(2) symmetry breaking give rise to very good predictions for the quark and lepton masses and mixing angles. The prediction of our model for the |U_{e\nu_{3}}| element in the Maki-Nakagawa-Sakata (MNS) matrix is close to the sensitivity of current experiments; thus the validity of our model can be tested in the near future. We also investigate the correlation between the |U_{e\nu_{3}}| element and \tan^{2}\theta_{\odot} in a general two-zero neutrino mass texture.Comment: RevTeX4; 9 pages; 1 figur

Constraints on the rare tau decays from mu --> e gamma in the supersymmetric see-saw model

It is now a firmly established fact that all family lepton numbers are violated in Nature. In this paper we discuss the implications of this observation for future searches for rare tau decays in the supersymmetric see-saw model. Using the two loop renormalization group evolution of the soft terms and the Yukawa couplings we show that there exists a lower bound on the rate of the rare process mu --> e gamma of the form BR(mu --> e gamma) > C BR(tau --> mu gamma) BR(tau --> e gamma), where C is a constant that depends on supersymmetric parameters. Our only assumption is the absence of cancellations among the high-energy see-saw parameters. We also discuss the implications of this bound for future searches for rare tau decays. In particular, for large regions of the mSUGRA parameter space, we show that present B-factories could discover either tau --> mu gamma or tau --> e gamma, but not both.Comment: 39 pages, 7 figures. Typos corrected, references adde

Could One Find Petroleum Using Neutrino Oscillations in Matter?

In neutrino physics, it is now widely believed that neutrino oscillations are influenced by the presence of matter, modifying the energy spectrum produced by a neutrino beam traversing the Earth. Here, we will discuss the reverse problem, i.e. what could be learned about the Earth's interior from a single neutrino baseline energy spectrum, especially about the Earth's mantle. We will use a statistical analysis with a low-energy neutrino beam under very optimistic assumptions. At the end, we will note that it is hard to find petroleum with such a method, though it is not too far away from technical feasibility.Comment: 6 pages, 4 figures, EPL LaTeX. Final version to be published in Europhys. Let