Estimation of the composition of ultra-high energy cosmic rays using the muon correlation method based on Yakutsk EAS array data

In this article a new method is proposed for estimating the mass composition of cosmic rays in individual events with energies above $1.25\times 10^{19}$ eV. It is based on a joint analysis of experimental data and simulation results obtained using the QGSjet-II.04 model for muons with threshold energy $E_\mu= 1.0\times\cos\theta$ GeV in air showers with zenith angles up to $60^\circ$. The data from ground-based and underground scintillation detectors of the Yakutsk EAS array were used. Separate groups of nuclei and other primary particles were found.