Measurements of All-Particle Energy Spectrum and Mean Logarithmic Mass of Cosmic Rays from 0.3 to 30 PeV with LHAASO-KM2A
Z. Cao, F. Aharonian, Axikegu, Y. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, A. V. Bukevich, Qiku Cao, Wenjing Cao, Zhe Cao, J. Chang, Jin Chang, A. M. Chen, E. S. Chen, H. X. Chen, Liang Chen, Lin CHEN, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, Shaw H. Chen, Shaw H. Chen, S. Z. Chen, T. L. Chen, Yuyi Chen, Ning Cheng, Yaodong Cheng, Maxwell Cui, S. W. Cui, Xiaohong Cui, Y. D. Cui, B. Z. Dai, H. L. Dai, Zi-Gao Dai, Danzengluobu Danzengluobu, X. Q. Dong, K. K. Duan, J. H. Fan, Yi-Zhong Fan, Jun Fang, J. H. Fang, Kun Fang, C. Feng, H. Feng, Lei Feng, S. H. Feng, X. T. Feng, Y. L. Feng, Y. L. Feng, S. Gabici, Bo Gao, C. D. Gao, Qi Gao, W. Gao, W. K. Gao, M. M. Ge, Li‐Sheng Geng, Gwenael Giacinti, G. Gong, Q. B. Gou, M. H. Gu, Fulai Guo, X. L. Guo, Y. Q. Guo, H. H. He, Y. A. Han, M. Hasan, X. B. He, H. N. He, Jiafa He, Y. He, Y. K. Hor, B. W. Hou, C. Hou, X. T. Hou, H. B. Hu, Qiang Hu, S. C. Hu, D. Huang, T. Q. Huang, W. J. Huang, X. T. Huang, X. Y. Huang, Yuanyuan Huang, Xiangdong Ji, H. Y. Jia, K. Jia, K. Jiang, X. W. Jiang, Z. J. Jiang, M. Jin, M.M Kang, T. Ke, D. Kuleshov, K. Kurinov, Bing Li
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.