A Gauge Mediation Model of Dynamical Supersymmetry Breaking without Color Instability

We construct a gauge mediation model of dynamical supersymmetry breaking (DSB) based on a vector-like gauge theory, in which there is a unique color-preserving true vacuum. The DSB scale $\Lambda/4\pi$ turns out to be as high as $\Lambda/4\pi \simeq 10^{8-9} GeV$, since the transmission of the DSB effects to the standard model sector is completed through much higher loops. This model is perfectly natural and phenomenologically consistent. We also stress that the dangerous D-term problem for the messenger U(1)_m is automatically solved by a charge conjugation symmetry in the vector-like gauge theory.Comment: 11 pages, Late

Limit on the Color-Triplet Higgs Mass in the Minimum Supersymmetric SU(5) Model

In the minimum supersymmetric SU(5) GUT, we derive the upper limit on the mass of the color-triplet Higgs multiplets as \mhc\leq 2.4\times 10^{16}~\GEV (90 \% C.L.) taking all possible corrections into account in a renormalization group analysis. If the above upper limit is compared with a limit on \mhc from the negative search for the proton decay; \mhc \geq 2.0\times 10^{16}~\GEV (in which effects of the larger top-quark mass are included), the minimum supersymmetric SU(5) GUT is severely constrained

Exact Event Rates of Lepton Flavor Violating Processes in Supersymmetric SU(5) Model

Event rates of various lepton flavor violating processes in the minimal supersymmetric SU(5) model are calculated, using exact formulas which include Yukawa vertices of lepton-slepton-Higgsino. We find subtlety in evaluating event rates due to partial cancellation between diagrams. This cancellation typically reduces the event rates significantly, and the size of the reduction strongly depends on superparticle mass spectrum.Comment: 11pages, 8 figures. Fig.5 where the mu-e conversion rates in nuclei was shown was incorrect due to an error in our numerical computation.It is replaced in this corrected version. All conclusions remain unchange

Neutrino Oscillations in an SO(10) SUSY GUT with U(2)xU(1)nU(2)xU(1)^{n} Family Symmetry

In a previous paper we analyzed fermion masses (focusing on neutrino masses and mixing angles) in an SO(10) SUSY GUT with U(2)\timesU(1)^n family symmetry. The model is "natural" containing all operators in the Lagrangian consistent with the states and their charges. With minimal family symmetry breaking vevs the model is also predictive giving a unique solution to atmospheric (with maximal $\nu_\mu \to \nu_\tau$ mixing) and solar (with SMA MSW $\nu_e \to \nu_s$ mixing) neutrino oscillations. In this paper we analyze the case of general family breaking vevs. We now find several new solutions for three, four and five neutrinos. For three neutrinos we now obtain SMA MSW, LMA MSW or vacuum oscillation solutions for solar neutrinos. In all three cases the atmospheric data is described by maximal $\nu_\mu \to \nu_\tau$ mixing. In the four and five neutrino cases, in addition to fitting atmospheric and solar data as before, we are now able to fit LSND data. All this is obtained with the additional parameters coming from the family symmetry breaking vevs; providing only minor changes in the charged fermion fits

A Solution for Little Hierarchy Problem and b --> s gamma

We show that all the parameters which destabilize the weak scale can be taken around the weak scale in the MSSM without conflicting with the SM Higgs mass bound set by LEP experiment. The essential point is that if the lightest CP-even Higgs h in the MSSM has only a small coupling to Z boson, g_{ZZh}, LEP cannot generate the Higgs sufficiently. In the scenario, the SM Higgs mass bound constrains the mass of the heaviest CP-even Higgs H which has the SM like g_{ZZH} coupling. However, it is easier to make the heaviest Higgs heavy by the effect of off-diagonal elements of the mass matrix of the CP-even Higgs because the larger eigenvalue of 2 times 2 matrix becomes larger by introducing off-diagonal elements. Thus, the smaller stop masses can be consistent with the LEP constraints. Moreover, the two excesses observed at LEP Higgs search can naturally be explained as the signals of the MSSM Higgs h and H in this scenario. One of the most interesting results in the scenario is that all the Higgs in the MSSM have the weak scale masses. For example, the charged Higgs mass should be around 130 GeV. This looks inconsistent with the lower bound obtained by the b --> s gamma process as m_{H^\pm}>350GeV. However, we show that the amplitude induced by the charged Higgs can naturally be compensated by that of the chargino if we take the mass parameters by which the little hierarchy problem can be solved. The point is that the both amplitudes have the same order of magnitudes when all the fields in the both loops have the same order of masses.Comment: 14 pages, 5 figures, input parameter slightly changed, figures replaced, references correcte

Reconstructing Mammalian Phylogenies: A Detailed Comparison of the Cytochrome b and Cytochrome Oxidase Subunit I Mitochondrial Genes

The phylogeny and taxonomy of mammalian species were originally based upon shared or derived morphological characteristics. However, genetic analyses have more recently played an increasingly important role in confirming existing or establishing often radically different mammalian groupings and phylogenies. The two most commonly used genetic loci in species identification are the cytochrome oxidase I gene (COI) and the cytochrome b gene (cyt b). For the first time this study provides a detailed comparison of the effectiveness of these two loci in reconstructing the phylogeny of mammals at different levels of the taxonomic hierarchy in order to provide a basis for standardizing methodologies in the future. Interspecific and intraspecific variation is assessed and for the first time, to our knowledge, statistical confidence is applied to sequence comparisons. Comparison of the DNA sequences of 217 mammalian species reveals that cyt b more accurately reconstructs their phylogeny and known relationships between species based on other molecular and morphological analyses at Super Order, Order, Family and generic levels. Cyt b correctly assigned 95.85% of mammal species to Super Order, 94.31% to Order and 98.16% to Family compared to 78.34%, 93.36% and 96.93% respectively for COI. Cyt b also gives better resolution when separating species based on sequence data. Using a Kimura 2-parameter p-distance (x100) threshold of 1.5–2.5, cyt b gives a better resolution for separating species with a lower false positive rate and higher positive predictive value than those of COI

Global Regulation by Horizontally Transferred Regulators Establishes the Pathogenicity of Escherichia coli

Enterohemorrhagic Escherichia coli is an emerging pathogen that causes diarrhea and hemolytic uremic syndrome. Much of the genomic information that affects virulence is acquired by horizontal transfer. Genes necessary for attaching and effacing lesions are located in the locus for enterocyte effacement (LEE) pathogenicity island. LEE gene transcription is positively regulated by Ler, which is also encoded by the LEE, and by Pch regulators, which are encoded at other loci. Here we identified genes whose transcription profiles were similar to those of the LEE genes, by comparing the effects of altering ler and pch transcript levels. We assigned these genes into two classes, according to their transcription profiles. By determining the binding profiles for Ler and Pch, we showed that both were involved in regulating one class of genes, but only Pch was involved in regulating the other class. Binding sites were found in the coding region as well as the promoter region of regulated genes, which include genes common to K12 strains as well as 0157-specific genes, suggesting that both act as a global regulator. These results indicate that Ler and Pch orchestrate the transcription of virulence genes, which are captured by horizontal transfer and scattered throughout the chromosome