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A new analysis strategy for detection of faint γ-ray sources with Imaging Atmospheric Cherenkov Telescopes
Becherini Y., Djannati-Ataï A., Marandon V., Punch M., Pita S.
Astroparticle Physics 34 (2011) 858-870 - http://hal.archives-ouvertes.fr/hal-00730208
Planète et Univers/Astrophysique/Phénomènes cosmiques de haute energie
Physique/Astrophysique/Phénomènes cosmiques de haute energie
Planète et Univers/Astrophysique/Instrumentation et méthodes pour l'astrophysique
Physique/Astrophysique/Instrumentation et méthodes pour l'astrophysique
A new analysis strategy for detection of faint γ-ray sources with Imaging Atmospheric Cherenkov Telescopes
Y. Becherini1, 2, A. Djannati-Ataï2, V. Marandon2, M. Punch2, S. Pita2
1 :  LLR - Laboratoire Leprince-Ringuet
CNRS : UMR7638 – IN2P3 – Polytechnique - X
Route de Saclay - 91128 Palaiseau Cedex
2 :  APC - UMR 7164 - AstroParticule et Cosmologie
CNRS : UMR7164 – IN2P3 – Observatoire de Paris – Université Paris VII - Paris Diderot – CEA : DSM/IRFU
APC - UMR 7164, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, case postale 7020, F-75205 Paris Cedex 13
A new background rejection strategy for γ-ray astrophysics with stereoscopic Imaging Atmospheric Cherenkov Telescopes (IACT), based on Monte Carlo (MC) simulations and real background data from the H.E.S.S. [High Energy Stereoscopic System, see [1].] experiment, is described. The analysis is based on a multivariate combination of both previously-known and newly-derived discriminant variables using the physical shower properties, as well as its multiple images, for a total of eight variables. Two of these new variables are defined thanks to a new energy evaluation procedure, which is also presented here. The method allows an enhanced sensitivity with the current generation of ground-based Cherenkov telescopes to be achieved, and at the same time its main features of rapidity and flexibility allow an easy generalization to any type of IACT. The robustness against Night Sky Background (NSB) variations of this approach is tested with MC simulated events. The overall consistency of the analysis chain has been checked by comparison of the real γ-ray signal obtained from H.E.S.S. observations with MC simulations and through reconstruction of known source spectra. Finally, the performance has been evaluated by application to faint H.E.S.S. sources. The gain in sensitivity as compared to the best standard Hillas analysis ranges approximately from 1.2 to 1.8 depending on the source characteristics, which corresponds to an economy in observation time of a factor 1.4 to 3.2.

Astroparticle Physics (Astropart. Phys.)
Publisher Elsevier
ISSN 0927-6505 
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