Expected energy spectrum of cosmic ray protons and helium below 4 PeV measured by LHAASO * * Supported by the National Key R&D Program of China (2018YFA0404201, 2018YFA0404202), the Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, CAS (Y5113D005C) and National Natural Science Foundation (NSFC) (11563004, 11775248)

Abstract

The Large High Altitude Air Shower Observatory (LHAASO) is a composite cosmic ray observatory consisting of three detector arrays: kilometer square array (KM2A), which includes the electromagnetic detector array and muon detector array, water Cherenkov detector array (WCDA) and wide field-of-view Cherenkov telescope array (WFCTA). One of the main scientific objectives of LHAASO is to precisely measure the cosmic rays energy spectrum of individual components from eV to eV. The hybrid observation will be employed by the LHAASO experiment, in which the lateral and longitudinal distributions of extensive air shower can be observed simultaneously. Thus, many kinds of parameters can be used for primary nuclei identification. In this paper, high purity cosmic ray simulation samples of the light nuclei component are obtained using multi-variable analysis. The apertures of 1/4 LHAASO array for pure proton and mixed proton and helium (H&He) samples are and , respectively. Prospect of obtaining proton and H&He spectra from 100 TeV to 4 PeV is discussed.