Abstract As ultra-high energy photons (EeV and beyond) propagate from their sources of production to Earth, radiation-matter interactions can occur, leading to an effective screening of the incident flux. In this energy domain, photons can undergo e + / e − pair production when interacting with the surrounding geomagnetic field, which in turn can produce a cascade of electromagnetic particles called preshower. Such cascade can initiate air showers in the Earth’s atmosphere that gamma-ray telescopes, such as the next-generation gamma-ray observatory Cherenkov Telescope Array, can detect through Cherenkov emission. In this paper, we study the feasibility of detecting such phenomenon using Monte-Carlo simulations of nearly horizontal air showers for the example of the La Palma site of the Cherenkov Telescope Array. We investigate the efficiency of multivariate analysis in correctly identifying preshower events initiated by 40 EeV photons and cosmic ray dominated background simulated in the energy range 10 TeV – 10 EeV. The effective areas for such kind of events are also investigated and event rate predictions related to different ultra-high energy photons production models are presented. While the expected number of preshowers from diffuse emission of UHE photons for 30 hours of observation is estimated around 3.3 × 10 − 5 based on the upper limits put by the Pierre Auger Observatory, this value is at the level of 2.7 × 10 − 4 ( 5.7 × 10 − 5 ) when considering the upper limits of the Pierre Auger Observatory (Telescope Array) on UHE photon point sources. However, UHE photon emission may undergo possible ”boosting” due to gamma-ray burst, increasing the expected number of preshower events up to 0.17 and yielding a minimum required flux of ~ 0.2 km − 2 yr − 1 to obtain one preshower event, which is about a factor 10 higher than upper limits put by the Pierre Auger Observatory and Telescope Array (0.034 and 0.019 km − 2 yr − 1 , respectively).

中文翻译：

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利用伽马射线望远镜通过预淋浴效应寻找超高能光子：CTA-North 效率研究

摘要 随着超高能光子（EeV 及更高）从其产生源传播到地球，可能会发生辐射物质相互作用，从而对入射通量进行有效屏蔽。在这个能量域中，光子在与周围的地磁场相互作用时可以产生 e + / e - 对，这反过来又可以产生一系列称为预淋浴的电磁粒子。这种级联可以在地球大气层中引发空气淋浴，伽马射线望远镜，例如下一代伽马射线天文台切伦科夫望远镜阵列，可以通过切伦科夫辐射进行探测。在本文中，我们以切伦科夫望远镜阵列的拉帕尔马站点为例，研究了使用近乎水平的空气淋浴的蒙特卡罗模拟来检测这种现象的可行性。我们研究了多变量分析在正确识别由 40 EeV 光子和在 10 TeV – 10 EeV 能量范围内模拟的宇宙射线主导背景引发的阵雨前事件的效率。还研究了此类事件的有效区域，并提出了与不同超高能光子产生模型相关的事件率预测。虽然根据皮埃尔·奥格天文台设定的上限，在 30 小时的观测中，UHE 光子漫射产生的预流星雨的预期数量估计约为 3.3 × 10 - 5，但该值处于 2.7 × 10 - 4 的水平（ 5.7 × 10 − 5 ) 当考虑到皮埃尔俄歇天文台（望远镜阵列）在 UHE 光子点源上的上限时。然而，由于伽马射线爆发，UHE 光子发射可能会受到“增强”，