7,364 research outputs found
Electron/Photon identification in ATLAS and CMS
Recent studies in ATLAS and CMS experiments for the reconstruction and
identification of electrons and photons using full Monte Carlo and testbeam
data are reportedComment: Talk given at the Hadron Collider Physic Symposium 2006 (HCP2006),
Durham, NC on behalf of ATLAS and CMS collaboration
Higgs search in HZZ/WW decay channels with the CMS detector
A prospective analysis for the search of the Standard Model Higgs boson
decaying in vector boson pairs is presented with the CMS experiment in the
context of the initial luminosity at the CERN LHC pp collider. Monte Carlo data
corresponding to an integrated luminosity of up to 1 fb are analysed and
the expected significance for a Standard Model-like Higgs boson in these
channels is established.Comment: 4 pages, 4 figures, proceedings of the Lake Louise Winter Institute
2009, 16th-21st February 2009, Alberta, Canad
Twelve Ways to Build CMS Crossings from ROOT Files
The simulation of CMS raw data requires the random selection of one hundred
and fifty pileup events from a very large set of files, to be superimposed in
memory to the signal event. The use of ROOT I/O for that purpose is quite
unusual: the events are not read sequentially but pseudo-randomly, they are not
processed one by one in memory but by bunches, and they do not contain orthodox
ROOT objects but many foreign objects and templates. In this context, we have
compared the performance of ROOT containers versus the STL vectors, and the use
of trees versus a direct storage of containers. The strategy with best
performances is by far the one using clones within trees, but it stays hard to
tune and very dependant on the exact use-case. The use of STL vectors could
bring more easily similar performances in a future ROOT release.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 8 pages, LaTeX, 1 eps figures. PSN
TUKT00
OVAL: the CMS Testing Robot
Oval is a testing tool which help developers to detect unexpected changes in
the behavior of their software. It is able to automatically compile some test
programs, to prepare on the fly the needed configuration files, to run the
tests within a specified Unix environment, and finally to analyze the output
and check expectations. Oval does not provide utility code to help writing the
tests, therefore it is quite independant of the programming/scripting language
of the software to be tested. It can be seen as a kind of robot which apply the
tests and warn about any unexpected change in the output. Oval was developed by
the LLR laboratory for the needs of the CMS experiment, and it is now
recommended by the CERN LCG project.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 5 pages, LaTeX, 0 eps figures. PSN
MOJT00
Theoretical Predictions for Surface Brightness Fluctuations and Implications for Stellar Populations of Elliptical Galaxies
(Abridged) We present new theoretical predictions for surface brightness
fluctuations (SBFs) using models optimized for this purpose. Our predictions
agree well with SBF data for globular clusters and elliptical galaxies. We
provide refined theoretical calibrations and k-corrections needed to use SBFs
as standard candles. We suggest that SBF distance measurements can be improved
by using a filter around 1 micron and calibrating I-band SBFs with the
integrated V-K galaxy color. We also show that current SBF data provide useful
constraints on population synthesis models, and we suggest SBF-based tests for
future models. The data favor specific choices of evolutionary tracks and
spectra in the models among the several choices allowed by comparisons based on
only integrated light. In addition, the tightness of the empirical I-band SBF
calibration suggests that model uncertainties in post-main sequence lifetimes
are less than +/-50% and that the IMF in ellipticals is not much steeper than
that in the solar neighborhood. Finally, we analyze the potential of SBFs for
probing unresolved stellar populations. We find that optical/near-IR SBFs are
much more sensitive to metallicity than to age. Therefore, SBF magnitudes and
colors are a valuable tool to break the age/metallicity degeneracy. Our initial
results suggest that the most luminous stellar populations of bright cluster
galaxies have roughly solar metallicities and about a factor of three spread in
age.Comment: Astrophysical Journal, in press (uses Apr 20, 2000 version of
emulateapj5.sty). Reposted version has a minor cosmetic change to Table
The Celestial Reference Frame at 24 and 43 GHz. II. Imaging
We have measured the sub-milli-arcsecond structure of 274 extragalactic
sources at 24 and 43 GHz in order to assess their astrometric suitability for
use in a high frequency celestial reference frame (CRF). Ten sessions of
observations with the Very Long Baseline Array have been conducted over the
course of 5 years, with a total of 1339 images produced for the 274
sources. There are several quantities that can be used to characterize the
impact of intrinsic source structure on astrometric observations including the
source flux density, the flux density variability, the source structure index,
the source compactness, and the compactness variability. A detailed analysis of
these imaging quantities shows that (1) our selection of compact sources from
8.4 GHz catalogs yielded sources with flux densities, averaged over the
sessions in which each source was observed, of about 1 Jy at both 24 and 43
GHz, (2) on average the source flux densities at 24 GHz varied by 20%-25%
relative to their mean values, with variations in the session-to-session flux
density scale being less than 10%, (3) sources were found to be more compact
with less intrinsic structure at higher frequencies, and (4) variations of the
core radio emission relative to the total flux density of the source are less
than 8% on average at 24 GHz. We conclude that the reduction in the effects due
to source structure gained by observing at higher frequencies will result in an
improved CRF and a pool of high-quality fiducial reference points for use in
spacecraft navigation over the next decade.Comment: 63 pages, 18 figures, 6 tables, accepted by the Astronomical Journa
Abundance patterns in early-type galaxies: is there a 'knee' in the [Fe/H] vs. [alpha/Fe] relation?
Early-type galaxies (ETGs) are known to be enhanced in alpha elements, in
accordance with their old ages and short formation timescales. In this
contribution we aim to resolve the enrichment histories of ETGs. This means we
study the abundance of Fe ([Fe/H]) and the alpha-element groups ([alpha/Fe])
separately for stars older than 9.5 Gyr ([Fe/H]o, [alpha/Fe]o) and for stars
between 1.5 and 9.5 Gyr ([Fe/H]i, [alpha/Fe]i). Through extensive simulation we
show that we can indeed recover the enrichment history per galaxy. We then
analyze a spectroscopic sample of 2286 early-type galaxies from the SDSS
selected to be ETGs. We separate out those galaxies for which the abundance of
iron in stars grows throughout the lifetime of the galaxy, i.e. in which
[Fe/H]o < [Fe/H]i. We confirm earlier work where the [Fe/H] and [alpha/Fe]
parameters are correlated with the mass and velocity dispersion of ETGs. We
emphasize that the strongest relation is between [alpha/Fe] and age. This
relation falls into two regimes, one with a steep slope for old galaxies and
one with a shallow slope for younger ETGs. The vast majority of ETGs in our
sample do not show the 'knee' in the plot of [Fe/H] vs. [alpha/Fe] commonly
observed in local group galaxies. This implies that for the vast majority of
ETGs, the stars younger than 9.5 Gyrs are likely to have been accreted or
formed from accreted gas. The properties of the intermediate-age stars in
accretion-dominated ETGs indicate that mass growth through late (minor) mergers
in ETGs is dominated by galaxies with low [Fe/H] and low [alpha/Fe]. The method
of reconstructing the stellar enrichment histories of ETGs introduced in this
paper promises to constrain the star formation and mass assembly histories of
large samples of galaxies in a unique way.Comment: 22 pages, 25 figures, accepted for publication by A&
Angular Sizes of Faint Field Disk Galaxies: Intrinsic Luminosity Evolution
In order to explain the small scale-lengths detected in the recent deep field
observations performed from large ground-based telescopes and from the Hubble
Space Telescope, we investigate the predictions at high redshifts for disk
galaxies that formed by infall. Changes with redshift in the observed
properties of field galaxies are directly related to the evolution of the disks
and of the stellar populations. We see that changes in the rest frame
luminosity of a galaxy induce smaller values of half-light radii than are
predicted assuming no evolution. Comparisons are presented with two observed
samples from Mutz et al. (1994) and Smail et al. (1995).Comment: plain tex file + 3 postscript figures. To be published in ApJ
Un procedimiento y una herramienta de ayuda a la decisión para desarrollar estrategias de rehabilitación energética sostenibles para la Directiva Europea (EPBD) 2010
The 2010 EPBD asks for an economic and social analysis in order to preserve social equity and to promote innovation and building productivity. This is possible with a life cycle energy cost (LCEC) analysis, such as with the SEC (Sustainable Energy Cost) model whose bottom up approach begins with a building typology including inhabitants. Then the analysis of some representative buildings includes the identification of a technico-economical optimum and energy retrofitting scenarios for each retrofitting programme and the extrapolation for the whole building stock. An extrapolation for the whole building stock allows to set up the strategy and to identify the needed means for reaching the objectives.
SEC is a decision aid tool for optimising sustainable energy retrofitting strategies for buildings at territorial and patrimonial scales inside a sustainable development approach towards the factor 4. Various versions of the SEC model are now available for housing and for tertiary buildings.La directiva europea de 2010 sobre eficiencia energética en los edificios exige un análisis económico y social con el objetivo de preservar la equidad social, promover la innovación y reforzar la productividad en la construcción.
Esto es posible con el análisis del coste global ampliado y especialmente con el modelo SEC. El análisis “bottom up” realizado con la SEC se basa en una tipología de edificio/usuario y en el análisis de edificios representativos: la identificación del óptimo técnico-económico y elaboración de escenarios antes de hacer una extrapolación al conjunto del parque.
SEC es una herramienta de ayuda a la decisión para desarrollar estrategias territoriales o patrimoniales de rehabilitación energética. Existen diversas versiones del modelo: para edificios residenciales (unifamiliares y plurifamiliares, públicos y privados) y para edificios terciarios
Nanostructured flexible implantable microelectrodes for stimulation and recording neural activity
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