10,559 research outputs found
Study of e+e- -> H+H- at a 800 GeV Linear Collider
The production and decay of heavy charged Higgs bosons at a 800 GeV e+e-
linear collider have been studied. The analysis of the H+H- -> tb tb, expected
to be dominant in the MSSM, and H+H- -> W+h0 W-h0 decay modes leading to the
same final state consisting of two W bosons and four b quarks, provides with a
determination of the boson mass to 1 GeV and of the production cross section
with 10% accuracy for 500 fb-1 of data.Comment: 4 pages, 1 figure, to appear in the Proceedings of the 5th Linear
Collider Workshop Fermilab, October 200
Hybrid Pixel Detector Development for the Linear Collider Vertex Tracker
In order to fully exploit the physics potential of the future high energy
e+e- linear collider, a Vertex Tracker able to provide particle track
extrapolation with very high resolution is needed. Hybrid Si pixel sensors are
an attractive technology due to their fast read-out capabilities and radiation
hardness. A novel pixel detector layout with interleaved cells has been
developed to improve the single point resolution. Results of the
characterisation of the first processed prototypes by electrostatic
measurements and charge collection studies are discussed.Comment: 5 pages, 1 figure, to appear in the Proceedings of the 9th Int.
Workshop on Vertex Detectors, Lake Michigan MI (USA), September~200
Influence of a specific aquatic program on social and gross motor skills in adolescents with Autism Spectrum Disorders: Three case reports
Swimming pool activities revealed to be efficacious to train psychomotor skills and increase adaptive behaviors in children with Autism Spectrum Disorders (ASD). Therefore, the purpose of this study was to investigate the efficacy of a specific multi-systemic aquatic therapy (CI-MAT) on gross motor and social skills in three adolescents with Autism Spectrum Disorders (ASD). Methods: three adolescents with ASD of which two boys (M1 with a chronological age of 10.3 years and a mental age of 4.7 years; M2 with a chronological age of 14.6 and a mental age inferior to 4 years) and one girl (chronological age of 14.0 and a mental age inferior to 4 years). The study was divided into three phases: baseline, 12-week CI-MAT program and Post-Test. Participants were administered a battery of tests incorporating anthropometric measurements, gross motor development test and a social skills questionnaire before and after a 12-week MAT-CI program. Results: Subjects improved locomotors and object control skills following the CI-MAT program in a different way. Concerning social behaviors, the higher proportion of gains was observed in the sensitivity of other's presence and eye contact, for the contact domain, and in the comply turn for the relationship domain. Conclusions: The results of this study showed that the CI-MAT program was effective for the development of gross-motor skills and social behaviors in subjects with ASD. Moreover there is an urge to carry out a whole psychological assessment targeting both motor and adaptive development suitable to provide educational and vocational plans of exercises for people with ASD
The sizes of galaxy halos in galaxy cluster Abell 1689
The multiple images observed in galaxy cluster Abell 1689 provide strong
constraints not only on the mass distribution of the cluster but also on the
ensemble properties of the cluster galaxies. Using parametric strong lensing
models for the cluster, and by assuming well motivated scaling laws between the
truncation radius s and the velocity dispersion sigma of a cluster galaxy we
are able to derive sizes of the dark matter halos of cluster galaxies.
For the scaling law expected for galaxies in the cluster environment (s
propto sigma), we obtain s = 64^{+15}_{-14} (sigma / 220 km/s) kpc. For the
scaling law used for galaxies in the field with s propto sigma^2 we find s =
66^{+18}_{-16} (sigma / 220 km/s)^2 kpc. Compared to halos of field galaxies,
the cluster galaxy halos in Abell 1689 are strongly truncated.Comment: 12 pages, 4 figures. Accepted for publication in the Ap
Heavy Quark Parameters and Vcb from Spectral Moments in Semileptonic B Decays
We extract the heavy quark masses and non-perturbative parameters from the
Delphi preliminary measurements of the first three moments of the charged
lepton energy and hadronic mass distributions in semileptonic B decays, using a
multi-parameter fit. We adopt two formalisms, one of which does not rely on a
1/mc expansion and makes use of running quark masses. The data are consistent
and the level of accuracy of the experimental inputs largely determines the
present sensitivity. The results allow to improve on the uncertainty in the
extraction of Vcb.Comment: 13 pages, 2 figure
Convex Polytopes and Quasilattices from the Symplectic Viewpoint
We construct, for each convex polytope, possibly nonrational and nonsimple, a
family of compact spaces that are stratified by quasifolds, i.e. each of these
spaces is a collection of quasifolds glued together in an suitable way. A
quasifold is a space locally modelled on modulo the action of a
discrete, possibly infinite, group. The way strata are glued to each other also
involves the action of an (infinite) discrete group. Each stratified space is
endowed with a symplectic structure and a moment mapping having the property
that its image gives the original polytope back. These spaces may be viewed as
a natural generalization of symplectic toric varieties to the nonrational
setting.Comment: LaTeX, 29 pages. Revised version: TITLE changed, reorganization of
notations and exposition, added remarks and reference
Studies of New Vector Resonances at the CLIC Multi-TeV e+e- Collider
Several models predict the existence of new vector resonances in the
multi-TeV region, which can be produced in high energy e+e- collisions in the
s-channel. In this paper we review the existing limits on the masses of these
resonances from LEP/SLC and TEVATRON data and from atomic parity violation in
some specific models. We study the potential of a multi-TeV e+e- collider, such
as CLIC, for the determination of their properties and nature.Comment: 17 pages, 16 EPS figures, uses JHEP3.cl
Role of the Calcium Plateau in the Neuronal Injury and Behavioral Morbidities Following Organophosphate Intoxication
Organophosphate (OP) chemicals include nerve agents and pesticides, and there is a growing concern of OP based chemical attacks against civilians. Current antidotes are essential in limiting immediate mortality associated with OP exposure. However, further research is needed to identify molecular mechanisms underlying long-term neurological deficits following survival of OP toxicity in order to develop effective therapeutics. We have developed rat survival models of OP induced status epilepticus (SE) that mimic chronic mortality and morbidity following OP intoxication. We have observed significant elevations in hippocampal calcium levels after OP SE that persisted for weeks following initial survival. Drugs inhibiting intracellular calcium-induced calcium release such as dantrolene, levetiracetam, and carisbamate lowered OP-SE mediated protracted calcium elevations. Given the critical role of calcium signaling in modulating behavior and cell-death mechanisms, drugs targeted at preventing the development of the calcium plateau could enhance neuroprotection, help reduce morbidity and improve outcome following survival of OP SE
Numerical simulations of chromospheric hard X-ray source sizes in solar flares
X-ray observations are a powerful diagnostic tool for transport,
acceleration, and heating of electrons in solar flares. Height and size
measurements of X-ray footpoints sources can be used to determine the
chromospheric density and constrain the parameters of magnetic field
convergence and electron pitch-angle evolution. We investigate the influence of
the chromospheric density, magnetic mirroring and collisional pitch-angle
scattering on the size of X-ray sources. The time-independent Fokker-Planck
equation for electron transport is solved numerically and analytically to find
the electron distribution as a function of height above the photosphere. From
this distribution, the expected X-ray flux as a function of height, its peak
height and full width at half maximum are calculated and compared with RHESSI
observations. A purely instrumental explanation for the observed source size
was ruled out by using simulated RHESSI images. We find that magnetic mirroring
and collisional pitch-angle scattering tend to change the electron flux such
that electrons are stopped higher in the atmosphere compared with the simple
case with collisional energy loss only. However, the resulting X-ray flux is
dominated by the density structure in the chromosphere and only marginal
increases in source width are found. Very high loop densities (>10^{11}
cm^{-3}) could explain the observed sizes at higher energies, but are
unrealistic and would result in no footpoint emission below about 40 keV,
contrary to observations. We conclude that within a monolithic density model
the vertical sizes are given mostly by the density scale-height and are
predicted smaller than the RHESSI results show.Comment: 19 pages, 9 figures, accepted for publication in Ap
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