Study of mass composition and energy spectrum of primary cosmic radiation by the imaging atmospheric Cherenkov technique

Imaging atmospheric Cherenkov telescopes (IACT) have proven to be, up to now, the most effective instruments for the observation of primary TeV gamma-radiation from astrophysical objects. The high detection rate as well as the capability of accurate reconstruction of air-shower parameters by the IACT technique also allow the use of the imaging technique for the study of the energy spectrum and mass composition of cosmic rays. In this paper we discuss the potential of this technique for the separation of different components of cosmic rays in the energy region 1-100 TeV amu(-1). We show that the imaging technique allows adequate separation of showers produced by protons from the contributions of all other nuclei, including alpha-particles, and thus allows a measurement of the energy spectrum of the proton component at TeV energies. Such measurements can currently be performed by operating single IACTs designed originally for gamma-ray astronomical purposes. The effective separation of different nucleus groups of the cosmic radiation is a more difficult problem. It benefits from the stereoscopic reconstruction of the shower development in the Earth's atmosphere. Our calculations show that simultaneous detection of air showers by two IACTs located at a distance of about 100 m from each other allows an effective separation of the proton, alpha-particle, medium (O), heavy (Si), and very heavy (Fe) groups of cosmic-ray nuclei.