The separation of air showers by the masses of the primary particles on the basis of the measured angular distributions of Cherenkov light at mountain level

A new method is considered for the separation of extensive air shower events according to the masses of primary particles on the basis of the directly measurable spatial-angular characteristics of Cherenkov light which is capable of distributing the showers between the three groups with small error probability in the framework of event-by-event approach in 1-100 PeV energy range. The results are described of the application of the method to the processing of the data of the optical part of the would-be detector setup of «Pamir-XXI» project. Quantitative indicators are given for the optimal and universal separation criteria, weak dependence of the latter on the night sky background and nuclear interaction model at super high energies and its superiority over the widely used Xmax parameter are demonstrated. The revealed characteristics of the method should be considered as the upper limits to approach to while constructing real detectors.