A new method for the UHECR mass composition studies

The detemination of the primary cosmic ray mass composition from the longitudinal development of atmospheric cascades is still an open problem. In this work we propose a new method of the multiparametric topological analysis and show that if both X${}_{max}$ - the depth of shower maximum and N${}_{max}$ - the number of charged particles in the shower maximum are used, reliable results can be obtained.