10,015 research outputs found
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
The Symplectic Penrose Kite
The purpose of this article is to view the Penrose kite from the perspective
of symplectic geometry.Comment: 24 pages, 7 figures, minor changes in last version, to appear in
Comm. Math. Phys
Multi-Higgs boson production in the Standard Model and beyond
We present a calculation of the loop-induced processes gg -> HH and gg ->
HHH, and investigate the observability of multi-Higgs boson production at the
CERN Large Hadron Collider (LHC) in the Standard Model (SM) and beyond. While
the SM cross sections are too small to allow observation at the LHC, we
demonstrate that physics beyond the SM can lead to amplified, observable cross
sections. Furthermore, the applicability of the heavy top quark approximation
in two- and three-Higgs boson production is investigated. We conclude that
multi-Higgs boson production at the SuperLHC is an interesting probe of Higgs
sectors beyond the SM and warrants further study.Comment: 17 pages, 17 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
Activated Tryptophan-Kynurenine metabolic system in the human brain is associated with learned fear
Fear is widely recognized as a defensive emotion that has developed as a consequence
of its adaptive function in protecting the entire animal kingdom from danger, ensuring
the survival (Bouton, 2002; Milad and Quirk, 2002). Although fear associated with specific
stimuli is an innate emotion (e.g., a loud noise triggering fear in infants, fear of potential
predators), it can also be acquired rapidly and permanently to enable an appropriate and
adaptive response to new or unpredictable environmental situations (LeDoux, 2000; Beckers
et al., 2013)
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
The StEllar Counterparts of COmpact high velocity clouds (SECCO) survey. II. Sensitivity of the survey and an Atlas of Synthetic Dwarf Galaxies
SECCO is a survey devoted to the search for stellar counterparts within Ultra
Compact High Velocity Clouds. In this contribution we present the results of a
set of simulations aimed at the quantitative estimate of the sensitivity of the
survey as a function of the total luminosity, size and distance of the stellar
systems we are looking for. For all our synthetic galaxies we assumed an
exponential surface brightness profile and an old and metal-poor population.
The synthetic galaxies are simulated both on the images and on the photometric
catalogs, taking into account all the observational effects. In the fields
where the available observational material is of the top quality we detect
synthetic galaxies as >=5 sigma over-densities of resolved stars down to
muV,h=30.0 mag/arcsec2, for D<=1.5 Mpc, and down to muV,h~29.5 mag/arcsec2, for
D<=2.5 Mpc. In the field with the worst observational material of the whole
survey we detect synthetic galaxies with muV,h<=28.8 mag/arcsec2 out to D<=1.0
Mpc, and those with muV,h<=27.5 mag/arcsec2 out to D<=2.5 Mpc. Dwarf galaxies
with MV=-10, with sizes in the range spanned by known dwarfs, are detected by
visual inspection of the images up to D=5 Mpc independently of the image
quality. In the best quality images dwarfs are partially resolved into stars up
to D=3.0 Mpc, and completely unresolved at D=5 Mpc. As an independent test of
the sensitivity of our images to low surface brightness galaxies we report on
the detection of several dwarf spheroidal galaxies probably located in the
Virgo cluster with MV<=-8.0 and muV,h<=26.8 mag/arcsec2. The nature of the
previously discovered SECCO 1 stellar system, also likely located in the Virgo
cluster, is re-discussed in comparison with these dwarfs. While specific for
the SECCO survey, our study may also provide general guidelines for detection
of faint stellar systems with 8m class telescopes.Comment: accepted for publication on A&
Testing the Higgs Mechanism in the Lepton Sector with multi-TeV e+e- Collisions
Multi-TeV e+e- collisions provide with a large enough sample of Higgs bosons
to enable measurements of its suppressed decays. Results of a detailed study of
the determination of the muon Yukawa coupling at 3 TeV, based on full detector
simulation and event reconstruction, are presented. The muon Yukawa coupling
can be determined with a relative accuracy of 0.04 to 0.08 for Higgs bosons
masses from 120 GeV to 150 GeV, with an integrated luminosity of 5 inverse-ab.
The result is not affected by overlapping two-photon background.Comment: 6 pages, 2 figures, submitted to J Phys G.: Nucl. Phy
A Study of depletion of fragmentation particles at small angles in b-jets with the DELPHI detector at LEP
Exciting dark matter in the galactic center
We reconsider the proposal of excited dark matter (DM) as an explanation for
excess 511 keV gamma rays from positrons in the galactic center. We
quantitatively compute the cross section for DM annihilation to nearby excited
states, mediated by exchange of a new light gauge boson with off-diagonal
couplings to the DM states. In models where both excited states must be heavy
enough to decay into e^+ e^- and the ground state, the predicted rate of
positron production is never large enough to agree with observations, unless
one makes extreme assumptions about the local circular velocity in the Milky
Way, or alternatively if there exists a metastable population of DM states
which can be excited through a mass gap of less than 650 keV, before decaying
into electrons and positrons.Comment: Dedicated to the memory of Lev Kofman; 16 pages, 9 figures; v3 added
refs, minor changes, accepted to PR
- …