Speaker
Description
Light component (H&He) energy spectrum of 125 TeV - 3 PeV is measured by the ARGO-YBJ detector with a wide field-of-view imaging Cherenkov telescope.
1.filling the gap between the direct observations of CREAM and the EAS xperiment, such as KASCADE;
2.The knee of (700±230_stat.±70_sys.) TeV is found with a significance of 4.2 sigma;
3.Spectra index: β_1=-2.56 ± 0.05 below the knee; β_2=-3.24 ± 0.36 above the knee;
4.Energy resolution: ~25% with offset <3%.
With the minimal assumption, the knee of the pure proton spectrum is derived to be at the same energy of 700 TeV. Taking into account the constraint of CREAM’s measurement at energies below 100 TeV, the proton and Helium spectra above the knee are discussed even if they are model dependent. The bending energy of Helium spectrum above 4X700 TeV, as the expectation of the model with E_b proportional to A, seems to be ruled out. A high precision measurement of the H&He and pure proton spectra in the energy range from 0.7 to 3 PeV is very crucial. LHAASO as the next generation high altitude EAS array with a combination of many detecting techniques will finish the measurement in few years.
