1,137 research outputs found
Low x particle spectra in the Modified Leading Logarithm Approximation
We show that the higher moments of the evolution obtained from the Modified
Leading Logarithm Approximation may be regarded as spurious higher order terms
in perturbation theory, and that neglecting them leads to a good description of
the data around and above the peak in . Furthermore, we use this
study of the moments to show that at high energy the Limiting Spectrum with
Local Parton-Hadron Duality may also be derived from the Modified Leading
Logarithm Approximation without any non-perturbative assumptions.Comment: Submitted to Eur. Phys. J.,
The dysfunctional host response to influenza A H7N9: a potential treatment option?
The newly emerging human pathogen influenza A H7N9 represents a potentially major threat to human health. The virus was first shown to be pathogenic in humans in 2013, and outbreaks continue to occur in China to the present time. The current incident mortality rate is disturbingly high despite the frequent use of antiviral therapy and intensive care management. If the virus gains the capacity for efficient person-to-person transmission, a global influenza pandemic could ensue with devastating consequences. In the absence of an effective vaccine, targeted regulation of the host immune response by immune modulators might be considered. Readily available, approved drugs with immune-modulating activities might prove to be a treatment option in combination with existing antiviral agents and supportive care
Leptonic Charged Higgs Decays in the Zee Model
We consider the version of the Zee model where both Higgs doublets couple to
leptons. Within this framework we study charged Higgs decays. We focus on a
model with minimal number of parameters consistent with experimental neutrino
data. Using constraints from neutrino physics we (i) discuss the reconstruction
of the parameter space of the model using the leptonic decay patterns of both
of the two charged Higgses, , and the decay
of the heavier charged Higgs, ; (ii) show that the
decay rate in general is enhanced in
comparision to the standard two Higgs doublet model while in some regions of
parameter space even dominates over
.Comment: 25 pages, 9 figure
Tests of the Standard Model: W mass and WWZ Couplings
Recent tests of the electroweak Standard Model are reviewed, covering the precise measurements of Z decays at LEP I and SLC and measurements of fermion pair production at higher energies at LEP II. Special emphasis is given to new results on W physics from LEP and FNAL
Altered sterol metabolism in budding yeast affects mitochondrial ironâsulfur (Fe-S) cluster synthesis
Ergosterol synthesis is essential for cellular growth and viability of the budding yeast Saccharomyces cerevisiae, and intracellular sterol distribution and homeostasis are therefore highly regulated in this species. Erg25 is an iron-containing C4-methyl sterol oxidase that contributes to the conversion of 4,4-dimethylzymosterol to zymosterol, a precursor of ergosterol. The ERG29 gene encodes an endoplasmic reticulum (ER)-associated protein, and here we identified a role for Erg29 in the methyl sterol oxidase step of ergosterol synthesis. ERG29 deletion resulted in lethality in respiring cells, but respiration-incompetent (Rho- or Rho0) cells survived, suggesting that Erg29 loss leads to accumulation of oxidized sterol metabolites that affect cell viability. Down-regulation of ERG29 expression in Îerg29 cells indeed led to accumulation of methyl sterol metabolites, resulting in increased mitochondrial oxidants and a decreased ability of mitochondria to synthesize iron-sulfur (Fe-S) clusters due to reduced levels of Yfh1, the mammalian frataxin homolog, which is involved in mitochondrial iron metabolism. Using a high-copy genomic library, we identified suppressor genes that permitted growth of Îerg29 cells on respiratory substrates, and these included genes encoding the mitochondrial proteins Yfh1, Mmt1, Mmt2, and Pet20, which reversed all phenotypes associated with loss of ERG29 Of note, loss of Erg25 also resulted in accumulation of methyl sterol metabolites and also increased mitochondrial oxidants and degradation of Yfh1. We propose that accumulation of toxic intermediates of the methyl sterol oxidase reaction increases mitochondrial oxidants, which affect Yfh1 protein stability. These results indicate an interaction between sterols generated by ER proteins and mitochondrial iron metabolism
Electroweak Physics, Experimental Aspects
Collider measurements on electroweak physics are summarised. Although the
precision on some observables is very high, no deviation from the Standard
Model of electroweak interactions is observed. The data allow to set stringent
limits on some models for new physics.Comment: Plenary Talk at the UK Phenomenology Workshop on Collider Physics,
Durham, 199
SUSY Magnetic Moments Sum Rules and Supersymmetry Breaking
It was recently shown that unbroken N=1 Susy relates, in a model independent
way, the magnetic transitions between states of different spin within a given
charged massive supermultiplet. We verify explicitly these sum rules for a
vector multiplet in the case of massless and massive fermions. The purpose of
this analysis is to provide the ground for the broken susy case. We study the
modifications of these results when an explicit soft Susy breaking realized
through a universal mass for all scalars is present. As a by-product we provide
a computation of the of the boson in the standard model which
corrects previous evaluations in the literature.Comment: 16+5 pages, Latex,(feynman.tex to print the figures), DFPD 94/TH/2
Unanswered Questions in the Electroweak Theory
This article is devoted to the status of the electroweak theory on the eve of
experimentation at CERN's Large Hadron Collider. A compact summary of the logic
and structure of the electroweak theory precedes an examination of what
experimental tests have established so far. The outstanding unconfirmed
prediction of the electroweak theory is the existence of the Higgs boson, a
weakly interacting spin-zero particle that is the agent of electroweak symmetry
breaking, the giver of mass to the weak gauge bosons, the quarks, and the
leptons. General arguments imply that the Higgs boson or other new physics is
required on the TeV energy scale. Indirect constraints from global analyses of
electroweak measurements suggest that the mass of the standard-model Higgs
boson is less than 200 GeV. Once its mass is assumed, the properties of the
Higgs boson follow from the electroweak theory, and these inform the search for
the Higgs boson. Alternative mechanisms for electroweak symmetry breaking are
reviewed, and the importance of electroweak symmetry breaking is illuminated by
considering a world without a specific mechanism to hide the electroweak
symmetry.
For all its triumphs, the electroweak theory has many shortcomings. . . .Comment: 31 pages, 20 figures; prepared for Annual Review of Nuclear and
Particle Science (minor changes
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