301 research outputs found
Heavy-meson physics and flavour violation with a single generation
We study flavour-violating processes which involve heavy B- and D-mesons and
are mediated by Kaluza-Klein modes of gauge bosons in a previously suggested
model where three generations of the Standard Model fermions originate from a
single generation in six dimensions. We find the bound on the size R of the
extra spatial dimensions 1/R>3.3 TeV, which arises from the three-body decay
B_s to K mu e. Due to the still too low statistics this bound is much less
stringent than the constraint arising from K to mu e, 1/R>64 TeV, which was
found in a previous work (Frere et al., JHEP, 2003). Nevertheless, we argue
that a clear signature of the model would be an observation of K to mu e and
B_s to K mu e decays without observations of other flavour and lepton number
changing processes at the same precision level.Comment: 15 page
Towards Z_2-protected gauge--Higgs unification
In theories with flux compactification in eight or higher dimensions, the
extra-dimensional components of the gauge field may be regarded as the Higgs
field candidates. We suggest a way to protect these components from getting
large tree-level masses by imposing a -symmetry acting on compact
manifolds and background fields on them. In our scheme the infinite series of
heavy KK modes naturally decouples from the light Higgs candidates, whose
number is generically larger than one. We also present toy models with three
families of leptons, illustrating that the Yukawa sector in our scheme is
fairly strongly constrained. In one of these models, one fermion gets a
tree-level mass after electroweak symmetry breaking, while two others remain
naturally massless at the tree level.Comment: A few points clarified. Journal versio
Zero Modes of Matter Fields on Scalar Flat Thick Branes
Zero modes of various matters with spin 0, 1 and 1/2 on a class of scalar
flat thick branes are discussed in this paper. We show that scalar field with
spin 0 is localized on all thick branes without additional condition, while
spin 1 vector field is not localized. In addition, for spin 1/2 fermionic
field, the zero mode is localized on the branes under certain conditions.Comment: 11 pages,no figure
Mucosal immune responses following intestinal nematode infection.
In most natural environments, the large majority of mammals harbour parasitic helminths that often live as adults within the intestine for prolonged periods (1-2 years). Although these organisms have been eradicated to a large extent within westernized human populations, those living within rural areas of developing countries continue to suffer from high infection rates. Indeed, recent estimates indicate that approximately 2.5 billion people worldwide, mainly children, currently suffer from infection with intestinal helminths (also known as geohelminths and soil-transmitted helminths) . Paradoxically, the eradication of helminths is thought to contribute to the increased incidence of autoimmune diseases and allergy observed in developed countries. In this review, we will summarize our current understanding of host-helminth interactions at the mucosal surface that result in parasite expulsion or permit the establishment of chronic infections with luminal dwelling adult worms. We will also provide insight into the adaptive immune mechanisms that provide immune protection against re-infection with helminth larvae, a process that is likely to be key to the future development of successful vaccination strategies. Lastly, the contribution of helminths to immune modulation and particularly to the treatment of allergy and inflammatory bowel disease will be discussed
Angular Momentum Conservation Law for Randall-Sundrum Models
In Randall-Sundrum models, by the use of general Noether theorem, the
covariant angular momentum conservation law is obtained with the respect to the
local Lorentz transformations. The angular momentum current has also
superpotential and is therefore identically conserved. The space-like
components of the angular momentum for Randall-Sundrum models are
zero. But the component is infinite.Comment: 10 pages, no figures, accepted by Mod. Phys. Lett.
Energy-momentum for Randall-Sundrum models
We investigate the conservation law of energy-momentum for Randall-Sundrum
models by the general displacement transform. The energy-momentum current has a
superpotential and are therefore identically conserved. It is shown that for
Randall-Sundrum solution, the momentum vanishes and most of the bulk energy is
localized near the Planck brane. The energy density is .Comment: 13 pages, no figures, v4: introduction and new conclusion added, v5:
11 pages, title changed and references added, accepted by Mod. Phys. Lett.
West Nile Virus Vaccination Protects against Usutu Virus Disease in Mice
West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne flaviviruses that can cause neuroinvasive disease in humans. WNV and USUV circulate in both Africa and Europe and are closely related. Due to antigenic similarity, WNV-specific antibodies and USUV-specific antibodies have the potential to bind heterologous viruses; however, it is unclear whether this interaction may offer protection against infection. To investigate how prior WNV exposure would influence USUV infection, we used an attenuated WNV vaccine that contains the surface proteins of WNV in the backbone of a dengue virus 2 vaccine strain and protects against WNV disease. We hypothesized that vaccination with this attenuated WNV vaccine would protect against USUV infection. Neutralizing responses against WNV and USUV were measured in vitro using sera following vaccination. Sera from vaccinated CD-1 and Ifnar1-/- mice cross-neutralized with WNV and USUV. All mice were then subsequently challenged with an African or European USUV strain. In CD-1 mice, there was no difference in USUV titers between vaccinated and mock-vaccinated mice. However, in the Ifnar1-/- model, vaccinated mice had significantly higher survival rates and significantly lower USUV viremia compared to mock-vaccinated mice. Our results indicate that exposure to an attenuated form of WNV protects against severe USUV disease in mice and elicits a neutralizing response to both WNV and USUV. Future studies will investigate the immune mechanisms responsible for the protection against USUV infection induced by WNV vaccination, providing critical insight that will be essential for USUV and WNV vaccine development.Funding for this project was provided by NIH NIAID R21 AI53988. Support was also provided by the Virginia–Maryland College of Veterinary Medicine IRC.S
Are the New Physics Contributions from the Left-Right Symmetric Model Important for the Indirect CP Violation in the Neutral B Mesons?
Several works analyzing the new physics contributions from the Left-Right
Symmetric Model to the CP violation phenomena in the neutral B mesons can be
found in the literature. These works exhibit interesting and experimentally
sensible deviations from the Standard Model predictions but at the expense of
considering a low right scale \upsilon_R around 1 TeV. However, when we stick
to the more conservative estimates for \upsilon_R which say that it must be at
least 10^7 GeV, no experimentally sensible deviations from the Standard Model
appear for indirect CP violation. This estimate for \upsilon_R arises when the
generation of neutrino masses is considered. In spite of the fact that this
scenario is much less interesting and says nothing new about both the CP
violation phenomenon and the structure of the Left-Right Symmetric Model, this
possibility must be taken into account for the sake of completeness and when
considering the see-saw mechanism that provides masses to the neutrino sector.Comment: LaTex file. 19 pages, 4 figures. Change in the way the paper address
the problem. As a result, change in title, abstract, and some sections.
Conclusions unchanged. Version to appear in Foundations of Physics Letter
Fermion masses and quantum numbers from extra dimensions
We study the localization of fermions on a brane embedded in a space-time
with geometry. Quantum numbers of localized fermions are
associated with their rotation momenta around the brane. Fermions with
different quantum numbers have different higher-dimensional profiles. Fermion
masses and mixings, which are proportional to the overlap of higher-dimensional
profiles of the fermions, depend on the fermion quantum numbers.Comment: 14 page
Thermal production of axino Dark Matter
We reconsider thermal production of axinos in the early universe, adding: a)
missed terms in the axino interaction; b) production via gluon decays
kinematically allowed by thermal masses; c) a precise modeling of reheating. We
find an axino abunance a few times larger than previous computations.Comment: 6 pages, 2 figures. Final version, to appear on JHE
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