Recently, the LHAASO collaboration published their latest result onPhys. Rev. Lett.. Using the observations with an array of thousands of particle detectors, LHAASO uncovered an important clue aboutthe cosmic rays that originate from outside of our Galaxy.

The cosmic rays pummeling Earth’s atmosphere are atoms stripped of their electrons and accelerated to high energies. Where and how cosmic rays are accelerated remains uncertain. The LHAASO measurement reveals the most precise characterization of the knee so far.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. Thisshed new light on the knee’s origin, which has perplexed astronomers and physicists for nearly 70 years.

The corresponding authors of this work are FENG Cun-feng, ZHANG Heng-yin and HE Hui-hai. FENG Chun-feng is the professor of Shandong University and ZHANG Heng-yin received her Ph.D. from Shandong University at 2021. Researchers in SDU have undertaken the work of theinvestigation and test of the particle detectors, as well as the development of the software framework, and have made remarkable achievements in a number of physical analysis.

Reference:

Z. Cao et al. (LHAASO Collaboration), “Measurements of all-particle energy spectrum and mean logarithmic mass of cosmic rays from 0.3 to 30 PeV with LHAASO-KM2A,” Phys. Rev. Lett. 132, 131002 (2024).