Zenith-Angular Characteristics of Particles in EASs with $E_0\simeq {10}^{18}$ eV According to the Yakutsk Array Data

Particle lateral distributions were investigated in cosmic ray air showers with energy $E_0\simeq {10}^{18}$ eV registered at the Yakutsk array with surface and underground scintillation detectors with $\simeq 1\times \sec \theta$~GeV threshold during the period of continuous observations from 1986 to 2016. The analysis covers events with arrival direction zenith angles $\theta \le {60}^{\circ }$ within five intervals with step $\mathrm{\Delta }\cos \theta =0.1$. Experimental values were compared to simulation results obtained with the use of CORSIKA code within the framework of QGSJet01 hadron interaction model. The whole dataset points at probable cosmic ray composition which is close to protons.