Phenomena have been observed in mountain high-energy cosmic-ray experiments, namely, a delayed absorption of high-energy cascades initiated by cosmic-ray hadrons in a lead absorber at $E_0\gtrsim {10}^{14} \mathrm{e}\mathrm{V}$ (so-called long-flying component), a coplanarity of most energetic particles in the central region of γ-ray−hadron superfamilies, and the so-called Tien Shan effect in EAS cores at $E_0\gtrsim {10}^{16} \mathrm{e}\mathrm{V} \left(\sqrt{s}>5 \mathrm{T}\mathrm{e}\mathrm{V}\right)$. These effects are not described by theoretical models. The coplanarity is explained by the process of coplanar generation of most energetic secondary particles in interactions of superhigh-energy hadrons with the nuclei of air atoms. The other two phenomena are possibly explained with a high cross section for fragmentation-region charmed-hadron generation. To investigate these phenomena, a cosmic-ray detector array, including a very thick ionization calorimeter, is being upgraded to study EAS cores.

The study describes the experimental complex of the station located in the Tien Shan mountains at an elevation of 3340 m above sea level. The complex consists of detectors of different types scattered across the station area, such as scintillation particles detectors, Cherenkov detectors, radio emission detectors for the measurement of the electron component of extensive air showers (EAS) created by the (1–1000) PeV cosmic ray particles, an ionization calorimeter and neutron detectors for the study of the nuclear-active component of EAS cores, and the underground particle detectors for the detection of cosmic ray muons. The data acquisition system allows the simultaneous recording of parameters from various stand-alone detectors registering an EAS, and storage of the acquired data in the database. As an illustration of research capability, the results of the EAS study are presented here which were obtained during the last few years at the different experimental set-ups constituting the Tien Shan complex.

In high-altitude experiments to study the central cores of EAS at E₀ ≳ 10¹⁶ eV (√s ≳ 5 TeV) using X-ray emulsion chambers and ionization calorimeters, phenomena such as the coplanarity of the arrival of the most energetic particles in super families of γ-rays and hadrons and a so-called Tien Shan effect (too slow absorption of cascades initiated by high-energy hadrons in the calorimeter) were observed. These effects could not be reproduced within the framework of theoretical models of the 80s and 90s. The coplanarity is explained via a process of coplanar generation of the most energetic secondary particles in interactions of super high-energy hadrons with nuclei of air atoms. Perhaps the Tien Shan effect could be explained using a high cross section for the generation of fragmentation-region charmed hadrons. To study these phenomena, a new set of detectors has been developed, including the world’s highest high-mountain ionization calorimeter, “Hadron-55”. This paper presents the initial experimental results.

The problem of the dependence of multiparticle reaction-product formation on the interactionregion size is considered both at cosmic-ray and accelerator energies. In cosmic rays, a comparative...