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arXiv · 2411.13793

Unveiling the nature of the knee in the cosmic ray energy spectrum

Huihai He·Hengying Zhang·Qinyi Cheng·Lingling Ma·Cunfeng Feng
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Abstract

The knee-like structure around 4 PeV is the most striking feature in the cosmic ray energy spectrum, whose origin remains enigmatic. We propose a novel concept of the total logarithmic mass energy spectrum to characterize the knee, taking into account LHAASO measurements of the all-particle energy spectrum and the mean logarithmic mass. The predominant role of proton in the knee formation is unearthed. The case of a mass-dependent knee is ruled out with a significance of 22.9${\sigma}$ and the rigidity-dependent knee feature is revealed. An ankle-like structure stemming from the excess of iron is discovered at 9.7${\pm}$ 0.2 PeV with a significance of 25.9${\sigma}$. Our findings pierce the mist of the puzzling knee for the first time since its discovery.

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Huihai He, Hengying Zhang, Qinyi Cheng, Lingling Ma, Cunfeng Feng. 2024-11-21. Unveiling the nature of the knee in the cosmic ray energy spectrum. https://arxiv.org/abs/2411.13793

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