Sensitivity of the large muon detector with the Tibet air-shower array to measure the primary proton spectrum between 40 and 630 TeV

Abstract

Abstract The Tibet ASγ group has been continuously observing cosmic rays and cosmic gamma rays above several TeV using the muon detector array (MD) and high-density Tibet air-shower array (Tibet-III) installed on the Tibet plateau at an altitude of 4300 m. The MD is a water Cherenkov pool array with a large effective area of 3400 m2 and has an excellent capability of primary selection using the number of muons in the shower. We report the sensitivity of the proton spectrum measurements for energies 40–630 TeV obtained via Monte Carlo simulations for an air-shower experiment. It was found that protons could be separated with a purity of 90%, and the survival ratio of protons including model dependence was 14.2%–19.1% and 3.7%–7.4% at about 35 TeV and about 450 TeV, respectively. The maximum total systematic error of the proton flux depending on interaction models in air-shower development and composition models was ±37%. With a large effective area and high proton separation capability, the Tibet ASγ experiment can measure the proton spectrum in the energy range from tens to hundreds of TeV with high statistical accuracy.