47 research outputs found
The Role of Subclass Switching in the Pathogenesis of Endemic Pemphigus Foliaceus
Endemic pemphigus foliaceus, like the sporadic form seen in the developed world, is mediated by IgG antibodies to desmoglein-1. We studied an endemic focus in Limao Verde, Brazil, where disease prevalence is 3.4%. We previously detected IgG antibodies to desmoglein-1 in 97% of patients, but also in 55% of normal subjects in the endemic focus, with progressively lower levels in normal subjects in surrounding areas. An environmental trigger is hypothesized to explain these and other findings. In this study we sought to determine if patients and enzyme-linked-immunosorbent-assay-positive normal subjects in Limao Verde differ in IgG subclass response to desmoglein-1. We developed a sensitive and specific subclass enzyme-linked immunosorbent assay using recombinant desmoglein-1 and standardized the assay to enable comparability between the four subclasses. We found that normal subjects have an IgG1 and IgG4 response, whereas patients have similar levels of IgG1 but a mean 19.3-fold higher IgG4 response. Patients in remission have a weak IgG4 response, and a 74.3-fold higher IgG4 response is associated with active disease. Finally, in five patients in whom we had blood samples from both before and after the onset of clinical disease, a mean 103.08-fold rise in IgG4 was associated with onset of clinical disease, but only a mean 3.45-fold rise in IgG1. These results suggest that the early antibody response in normal subjects living in the endemic area and in patients before the onset of clinical disease is mainly IgG1. Acquisition of an IgG4 response is a key step in the development of clinical disease
Diagonalization of the neutralino mass matrix and boson-neutralino interaction
We analyze a connection between neutralino mass sign, parity and structure of
the neutralino-boson interaction. Correct calculation of spin-dependent and
spin-independent contributions to neutralino-nuclear scattering should consider
this connection. A convenient diagonalization procedure, based on the
exponetial parametrization of unitary matrix, is suggested.Comment: 21 pages, RevTex
Discriminating graviton exchange effects from other new physics scenarios in e^+e^- collisions
We study the possibility of uniquely identifying the effects of graviton
exchange from other new physics in high energy e^+e^- annihilation into
fermion-pairs. For this purpose, we use as basic observable a specific
asymmetry among integrated differential distributions, that seems particularly
suitable to directly test for such gravitational effects in the data analysis.Comment: 18 pages, including figures; v2: additional references and
acknowledgements. To appear in PR
Black Holes and Instabilities of Negative Tension Branes
We consider the collision in 2+1 dimensions of a black hole and a negative
tension brane on an orbifold. Because there is no gravitational radiation in
2+1 dimensions, the horizon area shrinks when part of the brane falls through.
This provides a potential violation of the generalized second law of
thermodynamics. However, tracing the details of the dynamical evolution one
finds that it does not proceed from equilibrium configuration to equilibrium
configuration. Instead, a catastrophic space-time singularity develops similar
to the `big crunch' of FRW space-times. In the context of classical
general relativity, our result demonstrates a new instability of constructions
with negative tension branes.Comment: 18 pages, 3 figures, uses RevTeX. Minor typos fixed. References and
one footnote adde
Bounds on the dipole moments of the tau-neutrino via the process in a 331 model
We obtain limits on the anomalous magnetic and electric dipole moments of the
through the reaction
and in the framework of a 331 model. We consider initial-state radiation, and
neglect and photon exchange diagrams. The results are based on the data
reported by the L3 Collaboration at LEP, and compare favorably with the limits
obtained in other models, complementing previous studies on the dipole moments.Comment: 13 pages, 4 figures, to be published in The European Physical J C.
arXiv admin note: substantial text overlap with arXiv:hep-ph/060527
Supersymmetry Without Prejudice at the LHC
The discovery and exploration of Supersymmetry in a model-independent fashion
will be a daunting task due to the large number of soft-breaking parameters in
the MSSM. In this paper, we explore the capability of the ATLAS detector at the
LHC ( TeV, 1 fb) to find SUSY within the 19-dimensional
pMSSM subspace of the MSSM using their standard transverse missing energy and
long-lived particle searches that were essentially designed for mSUGRA. To this
end, we employ a set of k previously generated model points in the
19-dimensional parameter space that satisfy all of the existing experimental
and theoretical constraints. Employing ATLAS-generated SM backgrounds and
following their approach in each of 11 missing energy analyses as closely as
possible, we explore all of these k model points for a possible SUSY
signal. To test our analysis procedure, we first verify that we faithfully
reproduce the published ATLAS results for the signal distributions for their
benchmark mSUGRA model points. We then show that, requiring all sparticle
masses to lie below 1(3) TeV, almost all(two-thirds) of the pMSSM model points
are discovered with a significance in at least one of these 11 analyses
assuming a 50\% systematic error on the SM background. If this systematic error
can be reduced to only 20\% then this parameter space coverage is increased.
These results are indicative that the ATLAS SUSY search strategy is robust
under a broad class of Supersymmetric models. We then explore in detail the
properties of the kinematically accessible model points which remain
unobservable by these search analyses in order to ascertain problematic cases
which may arise in general SUSY searches.Comment: 69 pages, 40 figures, Discussion adde
Phenomenology of Randall-Sundrum Black Holes
We explore the phenomenology of microscopic black holes in the
Randall-Sundrum (RS) model. We consider the canonical framework in which both
gauge and matter fields are confined to the brane and only gravity spills into
the extra dimension. The model is characterized by two parameters, the mass of
the first massive graviton , and the curvature of the RS
anti-de Sitter space. We compute the sensitivity of present and future cosmic
ray experiments to various regions of and and compare with that
of Runs I and II at the Tevatron. As part of our phenomenological analysis, we
examine constraints placed on by AdS/CFT considerations.Comment: Version to appear in Physical Review D; contains additional analysis
on sensitivity of OW
Black Holes from Cosmic Rays: Probes of Extra Dimensions and New Limits on TeV-Scale Gravity
If extra spacetime dimensions and low-scale gravity exist, black holes will
be produced in observable collisions of elementary particles. For the next
several years, ultra-high energy cosmic rays provide the most promising window
on this phenomenon. In particular, cosmic neutrinos can produce black holes
deep in the Earth's atmosphere, leading to quasi-horizontal giant air showers.
We determine the sensitivity of cosmic ray detectors to black hole production
and compare the results to other probes of extra dimensions. With n \ge 4 extra
dimensions, current bounds on deeply penetrating showers from AGASA already
provide the most stringent bound on low-scale gravity, requiring a fundamental
Planck scale M_D > 1.3 - 1.8 TeV. The Auger Observatory will probe M_D as large
as 4 TeV and may observe on the order of a hundred black holes in 5 years. We
also consider the implications of angular momentum and possible exponentially
suppressed parton cross sections; including these effects, large black hole
rates are still possible. Finally, we demonstrate that even if only a few black
hole events are observed, a standard model interpretation may be excluded by
comparison with Earth-skimming neutrino rates.Comment: 30 pages, 18 figures; v2: discussion of gravitational infall, AGASA
and Fly's Eye comparison added; v3: Earth-skimming results modified and
strengthened, published versio
Solar Neutrino Masses and Mixing from Bilinear R-Parity Broken Supersymmetry: Analytical versus Numerical Results
We give an analytical calculation of solar neutrino masses and mixing at
one-loop order within bilinear R-parity breaking supersymmetry, and compare our
results to the exact numerical calculation. Our method is based on a systematic
perturbative expansion of R-parity violating vertices to leading order. We find
in general quite good agreement between approximate and full numerical
calculation, but the approximate expressions are much simpler to implement. Our
formalism works especially well for the case of the large mixing angle MSW
solution (LMA-MSW), now strongly favoured by the recent KamLAND reactor
neutrino data.Comment: 34 pages, 14 ps figs, some clarifying comments adde
Associated Production of a KK-Graviton with a Higgs Boson via Gluon Fusion at the LHC
In order to solve the hierarchy problem, several extra-dimensional models
have received considerable attention. We have considered a process where a
Higgs boson is produced in association with a KK-graviton () at the
LHC. At the leading order, this process occurs through gluon fusion mechanism
via a quark loop. We compute the cross section and
examine some features of this process in the ADD model. We find that the quark
in the loop does not decouple in the large quark-mass limit just as in the case
of process. We compute the cross section of this process for the case
of the RS model also. We examine the feasibility of this process being observed
at the LHC.Comment: 18 pages, 11 figures. Calculation in the Higgs effective theory
framework adde