Search for Delayed and Advanced Particles in the Interaction of Ultrahigh-Energy Cosmic Rays with the Earth’s Atmosphere in the Flow of EAS Muons at the MSU EAS Setup

The results obtained by studying temporal distributions of particles of energy in excess of 5 GeV in extensive air showers (EAS) of energy above \(10^{15}\) eV at distances shorter than 200 m from the EAS axis with the aim of searches in data from the MSU EAS setup for delayed and advanced new particles that could arise in the interactions of primary cosmic rays in the Earth’s atmosphere are presented. These investigations were performed with the aid of an unshielded ground-based detector and an underground detector shielded by a ground layer 20 m.w.e. thick. It is shown that delayed particles having a delay time between 100 and 300 ns and an exponentially descending temporal distribution with an exponent of 120 ns exhibit a higher ionizing ability than relativistic muons. The flow of such particles is attenuated by the ground layer between the unshielded and shielded detectors by a factor of about 30. Particles moving ahead of the EAS disk were not detected in the present study. Properties of delayed particles are discussed. Special features of calibrations and auxiliary tests confirming data from the present measurements are analyzed.