Measurements of Cosmic Ray Proton + Helium flux with the DAMPE experiment

This thesis concentrates on the measurement of cosmic-ray light component (proton + helium) spectrum with the Dark Matter Particle Explorer (DAMPE). In chapter one, an introduction on cosmic-ray history is given together with the acceleration mechanism and some recent experiments. A description on DAMPE system is presented in chapter two, which includes its sub-detectors, scientific targets and parameters. There are various challenges in measuring cosmic ray energy with a limited-size calorimeter (like the BGO of DAMPE). In chapter three, various unfolding methods for reconstructing the primary energy of cosmic ray nuclei are discussed. It turns out that the method based on the Bayes theorem has the best performance on reconstructing the cosmic-ray energy for DAMPE. The test results show that the Bayes method is capable of reconstructing nuclei energy with good accuracy on both MC samples (bias within 2%) and real data that come from the test beams at CERN (bias within 3%). In chapter four, a detailed description on the measurement of cosmic ray protons + helium spectrum is presented, which involves the candidates selection, energy reconstruction and calculation of the statistical and systematic uncertainties. Finally, the proton + helium spectrum with energy 40 GeV to 100 TeV is presented.