[en] Phenomenon of coplanar emission of hadrons in superhigh energy interactions is investigated by studying electromagnetic and nuclear cluster structure of γ-ray families detected in Pamir emulsion chamber experiment. Family selection by number of high energy clusters enable us to increase the effect/background ratio and to establish a clear energy threshold for production of coplanar events (E₀ ≅ 8 PeV)

[en] Parameters < R-bar >, < ER-bar > of gamma-hadron families with a visible energy Σ E_γ ≥ 100 TeV are analysed with the aim to prove their sensitivity to the mass composition of primary cosmic rays (PCR). The experimental values of these parameters are in agreement with the assumption that PCR become enriched with CNO nuclei at an energy ≥ 10¹⁶ PeV

[en] The attenuation length of the γ-families with Σ E_γ ≥ 100 TeV (N_fam = 1003), λ_att = (77 ± 3) g/cm² and their vertical intensity I_vert = 0.63 ± 0.04 m^-2·year^-1·sr^-1 are determined from the angular distribution. The experimental data are compared with model simulations

[en] The experimental spectrum of halo areas for gamma-families with Σ E_γ ≥ 500 TeV is obtained and compared with simulations in quark-gluon string model. The comparison suggests a ∼ 2 times decrease of the proton fraction in primary cosmic ray (PCR) composition in the energy region 10¹⁶/10¹⁷ eV. However at an energy above 10¹⁷ eV, the experimental flux of halo events with area exceeding 300/400 mm² is 5/10 times larger than the simulated one. Such a difference may be explained by the assumption that in this region the fraction of protons increases as much as 3 times, while the slope of the spectrum decreases (γ = 2.6/2.7)

[en] An appreciable fraction of gamma-families are accompanied by a halo, a narrow bundle of high-energy particles (energy density > 20 TeV/mm²) recorded in X-ray emulsion chambers as a diffuse dark spot in the central region of a gamma-family. Gamma-families in the experiment 'Pamir' are compared with simulations by three different codes of quark-gluon string model (MQ, MCO and QGSJet) based on extrapolating accelerator data up to energy E_o = 3 * 10¹⁸ eV and under various assumptions on mass composition of primary cosmic rays (PCR). The spectrum of halo area, S, is analyzed, especially at S > 100 mm². Simulations by different codes predict that at a PCR energy E_o ∼ 10¹⁸ eV the probability of initiating a halo with S ∼ 1000 mm² is 60% for primary protons and 40% for Fe nuclei. The fraction of protons in PCR composition at E₀ = 10¹⁶/10¹⁷ eV is estimated

[en] In the energy range above the PCR knee (5-1000 PeV), the emulsion chamber data exhibit some new features which are hard to explain in the framework of the Standard Model. In this survey (he results of a systematic quest of some new and exotic types of events which are observed in the Pamir emulsion chamber experiment are presented, namely, huge halo events, coplanar events, penetrating hadrons with abnormally weak absorption in lead, Centauro-type events. Possible theoretical approaches for their explanation are discussed

No abstract available

[en] The properties of atmospheric γ-families were studied at energy ranges below and above 500 TeV by aid of several emulsion chambers. Some characteristics of hadron interactions, e.g. the attenuation length in atmosphere, are discussed. Also presented are the energy spectra of γ-quanta and γ-families, multiplicity and lateral distance distributions, as well as energy-distance correlations. (BJ)

[en] Here we present a summary of joint discussions on the results of three mountain experiments with large-scale emulsion chambers, at Pamir, Mt. Fuji and Chacaltaya. Observations cover gamma quanta, hadrons and their clusters (called families). The following topics are covered, concerning the characteristics of nuclear interactions the energy region 10¹⁴-10¹⁶ eV: (i) rapid dissipation seen in atmospheric diffusion of high-energy cosmic-rays; (ii) multiplicity and Psub(t) increase in produced pi-mesons in the fragmentation region; (iii) existence of large-Psub(t) jets, (iv) extremely hadron-rich family of the Centauro type; (v) exotic phenomena in the extremely high energy region beyond 10¹⁶ eV. (orig.)

[en] The results of three-dimensional simulation of the nuclear and electromagnetic cascades (NEC) in atmosphere are presented. The simulation is based on the extrapolation of the accelerator data to the 10²-10⁵ TeV energy range assuming the existence of the Feynman scaling. (orig.)