1,875 research outputs found
Leptogenesis, Dark Matter and Higgs Phenomenology at TeV
We propose an interesting model of neutrino masses to realize leptogenesis
and dark matter at the TeV scale. A real scalar is introduced to naturally
realize the Majorana masses of the right-handed neutrinos. We also include a
new Higgs doublet that contributes to the dark matter of the universe. The
neutrino masses come from the vacuum expectation value of the triplet Higgs
scalar. The right-handed neutrinos are not constrained by the neutrino masses
and hence they could generate leptogenesis at the TeV scale without subscribing
to resonant leptogenesis. In our model, all new particles could be observable
at the forthcoming Large Hardon Collider or the proposed future International
Linear Collider.Comment: 7 pages, 3 figures. References added. Accepted by NP
Scale of SU(2)_R symmetry breaking and leptogenesis
Models of leptogenesis often invoke the out-of-equilibrium decays of heavy
right-handed neutrinos in order to create a baryon asymmetry of the universe
through the electroweak phase transition. Their presumed existence argues
strongly for the presence of an gauge symmetry. We study the
equilibrating effects of the resulting additional right-handed interactions and
find that successful leptogenesis requires that GeV if
, and
if , where is the mass of the lightest right-handed
neutrino. However, the option is excluded in a supersymmetric
theory with gravitinos.Comment: 4 pages (Revtex); accepted for publication with small modifications;
conclusions unchange
Influence of hyperhomocysteinemia on the cellular redox state - Impact on homocysteine-induced endothelial dysfunction
Hyperhomocysteinemia is an independent risk factor for the development of atherosclerosis. An increasing body of evidence has implicated oxidative stress as being contributory to homocysteines deleterious effects on the vasculature. Elevated levels of homocysteine may lead to increased generation of superoxide by a biochemical mechanism involving nitric oxide synthase, and, to a lesser extent, by an increase in the chemical oxidation of homocysteine and other aminothiols in the circulation. The resultant increase in superoxide levels is further amplified by homocysteinedependent alterations in the function of cellular antioxidant enzymes such as cellular glutathione peroxidase or extracellular superoxide dismutase. One direct clinical consequence of elevated vascular superoxide levels is the inactivation of the vasorelaxant messenger nitric oxide, leading to endothelial dysfunction. Scavenging of superoxide anion by either superoxide dismutase or 4,5-dihydroxybenzene 1,3-disulfonate (Tiron) reverses endothelial dysfunction in hyperhomocysteinemic animal models and in isolated aortic rings incubated with homocysteine. Similarly, homocysteineinduced endothelial dysfunction is also reversed by increasing the concentration of the endogenous antioxidant glutathione or overexpressing cellular glutathione peroxidase in animal models of mild hyperhomocysteinemia. Taken together, these findings strongly suggest that the adverse vascular effects of homocysteine are at least partly mediated by oxidative inactivation of nitric oxide
Supersymmetric Model of Neutrino Mass and Leptogenesis with String-Scale Unification
Adjoint supermultiplets (1,3,0) and (8,1,0) modify the evolution of gauge
couplings. If the unification of gauge couplings occurs at the string scale,
their masses are fixed at around GeV. This scale coincides with
expected gaugino condensation scale in the hidden sector GeV. We show how neutrino masses arise in this
unified model which naturally explain the present atmospheric and solar
neutrino data. The out-of-equilibrium decay of the superfield (1,3,0) at
GeV may also lead to a lepton asymmetry which then gets converted
into the present observed baryon asymmetry of the Universe.Comment: Improved by including constraints imposed by gravitino decay, new
references added, corrections and changes made. Accepted for publication in
Physics Letters.
Soft Leptogenesis in Higgs Triplet Model
We consider the minimal supersymmetric triplet seesaw model as the origin of
neutrino masses and mixing as well as of the baryon asymmetry of the Universe,
which is generated through soft leptogenesis employing a CP violating phase and
a resonant behavior in the supersymmetry breaking sector. We calculate the full
gauge--annihilation cross section for the Higgs triplets, including all
relevant supersymmetric intermediate and final states, as well as
coannihilations with the fermionic superpartners of the triplets. We find that
these gauge annihilation processes strongly suppress the resulting lepton
asymmetry. As a consequence of this, successful leptogenesis can occur only for
a triplet mass at the TeV scale, where the contribution of soft supersymmetry
breaking terms enhances the CP and lepton asymmetry. This opens up an
interesting opportunity for testing the model in future colliders.Comment: 17 pages, 5 figures; version accepted for publicatio
Constraints on neutrino masses from leptogenesis models
Upper bounds on the CP asymmetry relevant for leptogenesis are reexamined and
found weaker than in previous literature, both for hierarchical and for
quasi-degenerate right-handed neutrinos. Successful leptogenesis implies the
usual lower bound on right-handed neutrino masses, and an upper bound on
left-handed neutrino masses (which we obtain to be 0.15eV at 3sigma) only if
right-handed neutrinos are assumed to be much more hierarchical than
left-handed neutrinos. Otherwise both bounds can be considerably relaxed. The
constraint on light neutrino masses varies assuming different interpretations
of why neutrinos should be quasi-degenerate. With conservative assumptions, we
find that a mild quasi-degeneracy allows neutrinos heavier than an eV
compatibly with leptogenesis.
We also extend computations of thermal leptogenesis to an alternative model
of neutrino mass mediated by fermion triplets which was never considered so far
for leptogenesis. Leptogenesis can be successful despite the effect of gauge
interactions, resulting in only slightly stronger constraints on neutrino
masses.Comment: 16 pages, 6 figure
Cyber infrastructure for Fusarium: three integrated platforms supporting strain identification, phylogenetics, comparative genomics and knowledge sharing
The fungal genus Fusarium includes many plant and/or animal pathogenic species and produces diverse toxins. Although accurate species identification is critical for managing such threats, it is difficult to identify Fusarium morphologically. Fortunately, extensive molecular phylogenetic studies, founded on well-preserved culture collections, have established a robust foundation for Fusarium classification. Genomes of four Fusarium species have been published with more being currently sequenced. The Cyber infrastructure for Fusarium (CiF; http://www.fusariumdb.org/) was built to support archiving and utilization of rapidly increasing data and knowledge and consists of Fusarium-ID, Fusarium Comparative Genomics Platform (FCGP) and Fusarium Community Platform (FCP). The Fusarium-ID archives phylogenetic marker sequences from most known species along with information associated with characterized isolates and supports strain identification and phylogenetic analyses. The FCGP currently archives five genomes from four species. Besides supporting genome browsing and analysis, the FCGP presents computed characteristics of multiple gene families and functional groups. The Cart/Favorite function allows users to collect sequences from Fusarium-ID and the FCGP and analyze them later using multiple tools without requiring repeated copying-and-pasting of sequences. The FCP is designed to serve as an online community forum for sharing and preserving accumulated experience and knowledge to support future research and education
Type II Seesaw Higgs Triplet as the inflaton for Chaotic Inflation and Leptogenesis
In this paper, we consider a chaotic inflation model where the role of
inflaton is played by the Higgs triplet in type II seesaw mechanism for
generating the small masses of left-handed neutrinos. Leptogenesis could happen
after inflation. This model is constructed without introducing supersymmetry
(SUSY).Comment: 8 pages, 1 figure. Minor changes and a footnote added. Version to
publish in PL
- …