3,511 research outputs found
New results on direct CP violation in charged kaon decays by NA48/2
The NA48/2 result, based on the data collected during the 2003 run, on direct
CP violation in decay is presented. The main
goal of the experiment is to reach a sensitivity at level of in the
measurement of the charge asymmetry parameter , where
is the \emph{linear slope} of the Dalitz plot in the decay.
Thanks to the simultaneous collection of the two kaon charges and to the high
resolution of the main sub-detectors, the systematics uncertainties are kept
under the statistical error level. The experimental procedure, the analysis
technique and the main systematics are discussed to present the final result This result based on more than
events, correspondig to one half of the whole two year data taking, is about an
order of magnitude more precise with respect to the previous measurement.Comment: Talk given to "Rencontres de Moriond 2006 EW" on behalf of NA48/2
collaboratio
Large Size Telescope camera support structures for the Cherenkov Telescope Array
The design of the camera support structures for the Cherenkov Telescope Array
(CTA) Large Size Telescopes (LSTs) is based on an elliptical arch geometry
reinforced along its orthogonal projection by two symmetric sets of stabilizing
ropes. The main requirements in terms of minimal camera displacement, minimal
weight, minimal shadowing on the telescope mirror, maximal strength of the
structures and fast dynamical stabilization have led to the application of
Carbon Fibre Plastic Reinforced (CFPR) technologies. This work presents the
design, static and dynamic performance of the telescope fulfilling critical
specifications for the major scientific objectives of the CTA LST, e.g. Gamma
Ray Burst detection.Comment: In Proceedings of the 33rd International Cosmic Ray Conference
(ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223
Xeff analysis method optimization to enhance IACTs performances
The seek of high precision analyses in -ray astronomy leads to the
implementation of multivariate combination, benefiting from several
reconstruction methods. Such analysis, called , was developed for the
H.E.S.S. data using three shower reconstruction methods. This paper presents
the improvement granted to this analysis by refining the distribution
calculation of discriminant variables, considering observation conditions, and
adding new variables in the combination. The efficiency of the
analysis is presented using simulations and real data. A comparison with the
standard analysis (model++), for a typical set of sources, shows a significant
gain in sensitivity.Comment: Contribution to the Proceedings of the 34th International Cosmic Ray
Conference (ICRC 2015), The Hague, The Netherland
Observations of very high energy gamma-ray galactic sources with H.E.S.S.
International audienc
Sagittarius dwarf spheroidal galaxy observed by H.E.S.S
Dwarf spheroidal galaxies are characterized by a large measured mass-to-light
ratio and are not expected to be the site of high-luminosity non-thermal
high-energy gamma-ray emissions. Therefore they are among the most promising
candidates for indirect searches of dark matter particle annihilation signals
in gamma rays. The Sagittarius dwarf spheroidal galaxy has been regularly
observed by the High Energy Stereoscopic System (H.E.S.S.) of Cherenkov
telescopes for more than 90 hours, searching for TeV gamma-ray emission from
annihilation of dark matter particles. In absence of a significant signal, new
constraints on the annihilation crosssection of the dark matter particles
applicable for Majorana Weakly Interacting Massive Particles (WIMPs) are
derived.Comment: In Proceedings of the 33rd International Cosmic Ray Conference
(ICRC2013), Rio de Janeiro (Brazil
Optimization of multivariate analysis for IACT stereoscopic systems
Multivariate methods have been recently introduced and successfully applied
for the discrimination of signal from background in the selection of genuine
very-high energy gamma-ray events with the H.E.S.S. Imaging Atmospheric
Cerenkov Telescope. The complementary performance of three independent
reconstruction methods developed for the H.E.S.S. data analysis, namely Hillas,
model and 3D-model suggests the optimization of their combination through the
application of a resulting efficient multivariate estimator. In this work the
boosted decision tree method is proposed leading to a significant increase in
the signal over background ratio compared to the standard approaches. The
improved sensitivity is also demonstrated through a comparative analysis of a
set of benchmark astrophysical sources.Comment: 10 pages, 8 figures, 3 tables, accepted for publication in
Astroparticle Physic
A multivariate analysis approach for the Imaging atmospheric Cerenkov Telescopes System H.E.S.S.
International audienceWe present a multivariate classification approach applied to the analysis of data from the H.E.S.S. Very High Energy (VHE) gamma-ray IACT stereoscopic system. This approach combines three complementary analysis methods already successfully applied in the H.E.S.S. data analysis. The proposed approach, with the combined effective estimator Xeff, is conceived to improve the signal-to-background ratio and therefore particularly relevant to the morphological studies of faint extended sources
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