Analysis of the angular distributions of the direct Cherenkov light by the SPHERE-3 detector

In the present article we study the capability of a detector of the direct Cherenkov light intended for the future SPHERE-3 detector which is to separate the extensive air shower by the primary particle mass. For the purpose we analyze the angular distributions of light in detector and reveal the differences of their shapes for hydrogen, nitrogen and iron nuclei. Distribution shape are threated a few ways: with the use of threshold values and by approximating them with normal distribution. The lentgh of the distribution long axis is used as a parameter for the mass separation. We compare the efficiency of the parameter for the methods considered as well as for the integral and local criteria for different grid pitches of the angular distribution. In the conclusion we discuss the future plans to improve the approximation and to search for the other sensitive mass parameters.