Bimaximal Mixings from the Texture of the Right-handed Majorana Neutrino Mass Matrix

We study the origin of neutrino masses and mixing angles which can accomodate the LMA MSW solutions of the solar neutrino anomaly as well as the solution of the atmospheric neutrino problem, within the framework of the see-saw mechanism. We employ the diagonal form of the Dirac neutrino mass matrices with the physical masses as diagonal elements in the hierarchical order. Such choice has been motivated from the fact that the known CKM angles for the quark sector, are relatively small. We consider both possibilities where the Dirac neutrino mass matrix is either the charged lepton or the up-quark mass matrix within the framework of SO(10) GUT with or without supersymmetry. The non-zero texture of the right-handed Majorana neutrino mass matrix $M_{R}$ is used for the generation of the desired bimaximal mixings in a model independent way. Both hierarchical and inverted hierarchical models of the left-handed Majorana neutrino mass matrices are generated and then discussed with examples

Remark on the vectorlike nature of the electromagnetism and the electric charge quantization

In this work we study the structure of the electromagnetic interactions and the electric charge quantization in gauge theories of electroweak interactions based on semi-simple groups. We show that in the standard model of the electroweak interactions the structure of the electromagnetic interactions is strongly correlated to the quantization pattern of the electric charges. We examine these two questions also in all possible chiral bilepton gauge models of the electroweak interactions. In all they we can explain the vectorlike nature of the electromagnetic interactions and the electric charge quantization together demanding nonvanishing fermion masses and the anomaly cancellations.Comment: 17 pages, latex, no figure

Indications for an Extra Neutral Gauge Boson in Electroweak Precision Data

A new analysis of the hadronic peak cross section at LEP 1 implies a small amount of missing invisible width in Z decays, while the effective weak charge in atomic parity violation has been determined recently to 0.6% accuracy, indicating a significantly negative S parameter. As a consequence of these two deviations, the data are described well if the presence of an additional Z' boson, such as predicted in Grand Unified Theories, is assumed. Moreover, the data are now rich enough to study an arbitrary extra Z' boson and to determine its couplings in a model independent way. An excellent best fit to the data is obtained in this case, suggesting the possibility of a family non-universal Z' with properties similar to ones predicted in a class of superstring theories.Comment: 5 pages of ReVTeX, 2 figure

Nmr Solution Structure Of Plastocyanin From The Photosynthetic Prokaryote, Prochlorothrix Hollandica

The solution structure of a divergent plastocyanin (PC) from the photosynthetic prokaryote Prochlorothrix hollandica was determined by homonuclear H-1 NMR spectroscopy. Nineteen structures were calculated from 1222 distance restraints, yielding a family of structures having an average rmsd of 0.42 +/- 0.08 Angstrom, for backbone atoms and 0.71 +/- 0.07 Angstrom for heavy atoms to the mean structure. No distance constraint was violated by more than 0.26 Angstrom in the structure family. Despite the low number of conserved residues shared with other PC homologues, the overall folding pattern of P. hollandica PC is similar to other PCs, in that the protein forms a two-sheet beta-barrel tertiary structure. The greatest variability among the backbone structures is seen in the loop region from residues 47-60. The differences seen in the P. hollandica PC homologue likely arise due to a small deletion of 2-4 residues compared to the PC consensus; this yields a less extended loop containing a short alpha-helix from residues Ala52-Leu55. Additionally, the protein has an altered hydrophobic patch thought to be important in binding reaction partners. Whereas the backbone structure is very similar within the loops of the hydrophobic region, the presence of two unique residues (Tyr12 and Pro14) yields a structurally different hydrophobic surface likely important in binding P. hollandica Photosystem I

Lepton Flavor Violation and the Origin of the Seesaw Mechanism

The right--handed neutrino mass matrix that is central to the understanding of small neutrino masses via the seesaw mechanism can arise either (i) from renormalizable operators or (ii) from nonrenormalizable or super-renormalizable operators, depending on the symmetries and the Higgs content of the theory beyond the Standard Model. In this paper, we study lepton flavor violating (LFV) effects in the first class of seesaw models wherein the \nu_R Majorana masses arise from renormalizable Yukawa couplings involving a B-L = 2 Higgs field. We present detailed predictions for \tau -> \mu + \gamma and \mu -> e + \gamma branching ratios in these models taking the current neutrino oscillation data into account. Focusing on minimal supergravity models, we find that for a large range of MSSM parameters suggested by the relic abundance of neutralino dark matter and that is consistent with Higgs boson mass and other constraints, these radiative decays are in the range accessible to planned experiments. We compare these predictions with lepton flavor violation in the second class of models arising entirely from the Dirac Yukawa couplings. We study the dependence of the ratio r \equiv B(\mu -> e+\gamma)/B(\tau ->\mu +\gamma) on the MSSM parameters and show that measurement of r can provide crucial insight into the origin of the seesaw mechanism.Comment: 20 pages, Revtex, 7 figure

Solar neutrinos and grand unification

We consider the Grand Unification (GU) scenario for neutrino masses which is based on the see-saw mechanism with the mass of the heaviest right handed (RH) neutrino at the GU-scale: $M_3 \sim \Lambda_{GU}$, and on the quark-lepton symmetry for fermions from the third generation. The scenario predicts for the light neutrinos: $m_3 \sim (2 - 4) \cdot 10^{-3}$ eV and $m_2 \sim (0.3 - 3) \cdot 10^{-5}$ eV (in the case of a linear mass hierarchy of the RH neutrinos or/and in presence of the Planck scale suppressed non-renormalizable operators). It also predicts large $\nu_e - \nu_{\mu}$ mixing: $~\sin^2 2\theta_{e\mu} \stackrel{_>}{_\sim} 0.2$. In this scenario the solar neutrinos ($\nu_{\odot}$) undergo both the \nue $\to$ \nutau resonance conversion in the Sun and substantial \nue $\to$ \numu vacuum oscillations on the way from the Sun to the Earth. The interplay of both effects enlarges the range of neutrino parameters which solve the $\nu_{\odot}$-problem. In particular, $\nu_e - \nu_{\tau}$ mixing angle can be as small as the corresponding quark mixing: $\sin^2 2\theta_{e\tau} \geq (2~-~5) \cdot 10^{-4}$. The scenario predicts peculiar (oscillatory) distortion of the boron neutrino energy spectrum and seasonal variations of signals. Manifestations of these effects in the Super-Kamiokande and SNO experiments are studied.Comment: 36 pages, LaTeX, includes 14 figures, revised and expande

Universal Evolution of CKM Matrix Elements

We derive the two-loop evolution equations for the Cabibbo-Kobayashi-Maskawa matrix. We show that to leading order in the mass and CKM hierarchies the scaling of the mixings $|V_{ub}|^2$, $|V_{cb}|^2$, $|V_{td}|^2$, $|V_{ts}|^2$ and of the rephase-invariant CP-violating parameter $J$ is universal to all orders in perturbation theory. In leading order the other CKM elements do not scale. Imposing the constraint $\lambda _b=\lambda _{\tau}$ at the GUT scale determines the CKM scaling factor to be $\simeq 0.58$ in the MSSM.Comment: 17 pages + 2 figures not included (available upon request), revised version fixes discrepancy between S and S^{1/2}, no other changes, MAD/PH/72

An earthworm-like modular soft robot for locomotion in multi-terrain environments

Robotic locomotion in subterranean environments is still unsolved, and it requires innovative designs and strategies to overcome the challenges of burrowing and moving in unstructured conditions with high pressure and friction at depths of a few centimeters. Inspired by antagonistic muscle contractions and constant volume coelomic chambers observed in earthworms, we designed and developed a modular soft robot based on a peristaltic soft actuator (PSA). The PSA demonstrates two active configurations from a neutral state by switching the input source between positive and negative pressure. PSA generates a longitudinal force for axial penetration and a radial force for anchorage, through bidirectional deformation of the central bellows-like structure, which demonstrates its versatility and ease of control. The performance of PSA depends on the amount and type of fluid confined in an elastomer chamber, generating different forces and displacements. The assembled robot with five PSA modules enabled to perform peristaltic locomotion in different media. The role of friction was also investigated during experimental locomotion tests by attaching passive scales like earthworm setae to the ventral side of the robot. This study proposes a new method for developing a peristaltic earthworm-like soft robot and provides a better understanding of locomotion in different environments

Flavor Symmetry L_mu - L_tau and quasi-degenerate Neutrinos

Current data implies three simple forms of the neutrino mass matrix, each corresponding to the conservation of a non-standard lepton charge. While models based on L_e and L_e - L_mu - L_tau are well-known, little attention has been paid to L_mu - L_tau. A low energy mass matrix conserving L_mu - L_tau implies quasi-degenerate light neutrinos. Moreover, it is mu-tau symmetric and therefore (in contrast to L_e and L_e - L_mu - L_tau) automatically predicts maximal atmospheric neutrino mixing and zero U_{e3}. A see-saw model based on L_mu - L_tau is investigated and testable predictions for the neutrino mixing observables are given. Renormalization group running below and in between the see-saw scales is taken into account in our analysis, both numerically and analytically.Comment: 15 pages, 2 figures. Prepared for 5th International Conference on Nonaccelerator New Physics (NANP 05), Dubna, Russia, 20-25 Jun 200