The origin of ultra-high energy cosmic rays (UHECRs) is a long-standing mystery in astrophysics. Two collaborations are running experiments, the Telescope Array in the northern hemisphere and the Pierre Auger Observatory in the southern hemisphere, recording the signals coming from the extensive air showers made by the most energetic particles observed in nature, in search of their origin. We review the issues raised by the experimental results and discuss the possible origins of UHECR.

中文翻译：

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超高能宇宙射线

超高能宇宙射线（UHECR）的起源是天体物理学中一个长期存在的谜。两个合作正在进行实验，北半球的望远镜阵列和南半球的皮埃尔·奥格天文台，记录了自然界中观察到的最高能粒子产生的大范围风淋的信号，以寻找其起源。我们回顾了实验结果提出的问题，并讨论了UHECR的可能起源。