Search for high-energy photons and neutrinos, producing air showers with energy above $10^{18}$ eV by the Yakutsk array data

Abstract

A complex analysis of the data of the Yakutsk array has been carried out to search for primary photons that generate extensive air showers with energies above 10^18 eV. Within the framework of the integrated approach, a sample of showers with energies above 10^19 eV and zenith angles more than 60 degrees is separately considered to search for EAS produced by neutrinos. On the basis of calculations and experimental data, selection criteria were constructed and samples were sampled by these criteria for showers close in their characteristics to showers formed by primary photons. According to these data, the upper limit of the primary photon flux in the cosmic radiation of the limiting energies is estimated.