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arXiv 0704.3567astro-ph
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Cosmic-Ray事件作为大气切伦科夫望远镜成像的背景

Cosmic-Ray Events as Background in Imaging Atmospheric Cherenkov Telescopes

Gernot Maier, Johannes Knapp

摘要:

用成像大气切伦科夫望远镜观测50 GeV以上能量区域的伽马射线的主要背景是宇宙射线事件。大多数宇宙射线簇射的图像看起来与伽马射线的图像明显不同,因此很容易区分。然而,一小部分事件似乎与伽马射线无法区分。这就构成了观测高能伽马射线源的一个不可简化的背景,并限制了给定仪器所能达到的灵敏度。在这里,一个蒙特卡罗研究伽马类宇宙射线事件。类伽马宇宙射线事件的性质,簇射粒子是负责的类伽马外观,这些结果的依赖性的强子相互作用模型的选择进行了研究。大多数类伽马宇宙射线事件的特征是在簇射发展的早期产生高能π 0,将大部分簇射能量倾倒到电磁子簇射中。此外,来自单个μ子的切伦科夫光可以在附近的望远镜中模拟伽马射线。在收集面积的差异高达25%的QGSJet/FLUKA和Sibyll/FLUKA模拟之间的伽马类质子阵雨已被发现。

英文摘要:

The dominant background for observations of gamma-rays in the energy region above 50 GeV with Imaging Atmospheric Cherenkov telescopes are cosmic-ray events. The images of most of the cosmic ray showers look significantly different from those of gamma-rays and are therefore easily discriminated. However, a small fraction of events seems to be indistinguishable from gamma-rays. This constitutes an irreducible background to the observation of high-energy gamma-ray sources, and limits the sensitivity achievable with a given instrument. Here, a Monte Carlo study of gamma-like cosmic-ray events is presented. The nature of gamma-like cosmic-ray events, the shower particles that are responsible for the gamma-like appearance, and the dependence of these results on the choice of the hadronic interaction model are investigated. Most of the gamma-like cosmic ray events are characterised by the production of high-energy pi0's early in the shower development which dump most of the shower energy into electromagnetic sub-showers. Also Cherenkov light from single muons can mimic gamma-rays in close-by pairs of telescopes. Differences of up to 25% in the collection area for gamma-like proton showers between QGSJet/FLUKA and Sibyll/FLUKA simulations have been found.

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