Measurements of All-Particle Energy Spectrum and Mean Logarithmic Mass of 
Cosmic Rays from 0.3 to 30 PeV with LHAASO-KM2A

LHASSO Collaboration; Cao, Zhen; Aharonian, F.; Axikegu,; Y. X., Bai; Bao, Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Bian, W.; Bukevich, A. V.; Cao, Q.; Cao, W. Y.; Cao, Zhe; Chang, J.; Chang, J. F.; Chen, A. M.; Chen, E. S.; Chen, H. X.; Chen, Liang; Chen, Lin; Chen, Long; Chen, M. J.; Chen, M. L.; Chen, Q. H.; Chen, S.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen, Y.; Cheng, N.; Cheng, Y. D.; Cui, M. Y.; Cui, S. W.; Cui, X. H.; Cui, Y. D.; Dai, B. Z.; Dai, H. L.; Dai, Z. G.; Danzengluobu ,; X. Q., Dong; Duan, K. K.; Fan, J. H.; Fan, Y. Z.; Fang, J.; Fang, J. H.; Fang, K.; Feng, C. F.; Feng, H.; Feng, L.; Feng, S. H.; Feng, X. T.; Feng, Y.; Feng, Y. L.; Gabici, S.; Gao, B.; Gao, C. D.; Gao, Q.; Gao, W.; Gao, W. K.; Ge, M. M.; Geng, L. S.; Giacinti, G.; Gong, G. H.; Gou, Q. B.; Gu, M. H.; Guo, F. L.; Guo, X. L.; Guo, Y. Q.; Guo, Y. Y.; Han, Y. A.; Hasan, M.; He, H. H.; He, H. N.; He, J. Y.; He, Y.; Hor, Y. K.; Hou, B. W.; Hou, C.; Hou, X.; Hu, H. B.; Hu, Q.; Hu, S. C.; Huang, D. H.; Huang, T. Q.; Huang, W. J.; Huang, X. T.; Huang, X. Y.; Huang, Y.; Ji, X. L.; Jia, H. Y.; Jia, K.; Jiang, K.; Jiang, X. W.; Jiang, Z. J.; Jin, M.; Kang, M. M.; Karpikov, I.; Kuleshov, D.; Kurinov, K.; Li, B. B.; Li, C. M.; Li, Cheng; Li, Cong; Li, D.; Li, F.; Li, H. B.; Li, H. C.; Li, Jian; Li, Jie; Li, K.; Li, S. D.; Li, W. L.; Li, W. L.; Li, X. R.; Li, Xin; Li, Y. Z.; Li, Zhe; Li, Zhuo; Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu, C.; Liu, D.; Liu, D. B.; Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.; Liu, Y.; Liu, Y. N.; Luo, Q.; Luo, Y.; Lv, H. K.; Ma, B. Q.; Ma, L. L.; Ma, X. H.; Mao, J. R.; Min, Z.; Mitthumsiri, W.; Mu, H. J.; Nan, Y. C.; Neronov, A.; Ou, L. J.; Pattarakijwanich, P.; Pei, Z. Y.; Qi, J. C.; Qi, M. Y.; Qiao, B. Q.; Qin, J. J.; Raza, A.; Ruffolo, D.; Sáiz, A.; Saeed, M.; Semikoz, D.; Shao, L.; Shchegolev, O.; Sheng, X. D.; Shu, F. W.; Song, H. C.; Stenkin, Yu. V.; Stepanov, V.; Su, Y.; Sun, D. X.; Sun, Q. N.; Sun, X. N.; Sun, Z. B.; Takata, J.; Tam, P. H. T.; Tang, Q. W.; Tang, R.; Tang, Z. B.; Tian, W. W.; Wang, C.; Wang, C. B.; Wang, G. W.; Wang, H. G.; Wang, H. H.; Wang, J. C.; Wang, Kai; Wang, Kai; Wang, L. P.; Wang, L. Y.; Wang, P. H.; Wang, R.; Wang, W.; Wang, X. G.; Wang, X. Y.; Wang, Y.; Wang, Y. D.; Wang, Y. J.; Wang, Z. H.; Wang, Z. X.; Wang, Zhen; Wang, Zheng; Wei, D. M.; Wei, J. J.; Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, Q. W.; Wu, S.; Wu, X. F.; Wu, Y. S.; Xi, S. Q.; Xia, J.; Xiang, G. M.; Xiao, D. X.; Xiao, G.; Xin, Y. L.; Xing, Y.; Xiong, D. R.; Xiong, Z.; Xu, D. L.; Xu, R. F.; Xu, R. X.; Xu, W. L.; Xue, L.; Yan, D. H.; Yan, J. Z.; Yan, T.; Yang, C. W.; Yang, C. Y.; Yang, F.; Yang, F. F.; Yang, L. L.; Yang, M. J.; Yang, R. Z.; Yang, W. X.; Yao, Y. H.; Yao, Z. G.; Yin, L. Q.; Yin, N.; You, X. H.; You, Z. Y.; Yu, Y. H.; Yuan, Q.; Yue, H.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zha, M.; Zhang, B. B.; Zhang, F.; Zhang, H.; Zhang, H. M.; Zhang, H. Y.; Zhang, J. L.; Zhang, Li; Zhang, P. F.; Zhang, P. P.; Zhang, R.; Zhang, S. B.; Zhang, S. R.; Zhang, S. S.; Zhang, X.; Zhang, X. P.; Zhang, Y. F.; Zhang, Yi; Zhang, Yong; Zhao, B.; Zhao, J.; Zhao, L.; Zhao, L. Z.; Zhao, S. P.; Zhao, X. H.; Zheng, F.; Zhong, W. J.; Zhou, B.; Zhou, H.; Zhou, J. N.; Zhou, M.; Zhou, P.; Zhou, R.; Zhou, X. X.; Zhou, X. X.; Zhu, B. Y.; Zhu, C. G.; Zhu, F. R.; Zhu, H.; Zhu, K. J.; Zou, Y. C.; Zuo, X.

doi:10.1103/PhysRevLett.132.131002

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Measurements of All-Particle Energy Spectrum and Mean Logarithmic Mass of Cosmic Rays from 0.3 to 30 PeV with LHAASO-KM2A

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Aharonian, F.
Division Prof. Dr. James A. Hinton, MPI for Nuclear Physics, Max Planck Society;

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https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.132.131002
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https://arxiv.org/pdf/2403.10010.pdf
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Citation

LHASSO Collaboration, Cao, Z., Aharonian, F., Axikegu, Y. X., B., Bao, Y., et al. (2024). Measurements of All-Particle Energy Spectrum and Mean Logarithmic Mass of Cosmic Rays from 0.3 to 30 PeV with LHAASO-KM2A. Physical Review Letters, 132(13): 131002. doi:10.1103/PhysRevLett.132.131002.

Cite as: https://hdl.handle.net/21.11116/0000-000F-1E44-4

Abstract

We present the measurements of all-particle energy spectrum and mean logarithmic mass of cosmic rays in the energy range of 0.3–30 PeV using data collected from LHAASO-KM2A between September 2021 and December 2022, which is based on a nearly composition-independent energy reconstruction method, achieving unprecedented accuracy. Our analysis reveals the position of the knee at 3.67±0.05±0.15 PeV. Below the knee, the spectral index is found to be −2.7413±0.0004±0.0050, while above the knee, it is −3.128±0.005±0.027, with the sharpness of the transition measured with a statistical error of 2%. The mean logarithmic mass of cosmic rays is almost heavier than helium in the whole measured energy range. It decreases from 1.7 at 0.3 PeV to 1.3 at 3 PeV, representing a 24% decline following a power law with an index of −0.1200±0.0003±0.0341. This is equivalent to an increase in abundance of light components. Above the knee, the mean logarithmic mass exhibits a power law trend towards heavier components, which is reversal to the behavior observed in the all-particle energy spectrum. Additionally, the knee position and the change in power-law index are approximately the same. These findings suggest that the knee observed in the all-particle spectrum corresponds to the knee of the light component, rather than the medium-heavy components.