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

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.