[en] The results of data handling for the E-184 experiment involving the irradiation of the active target, consisting of carbon, silicon, and lead plates by a 70-GeV proton beam are presented. When the two-prong neutral charmed meson decay signal was selected and the cross section for charm production at a near-threshold energy was estimated (σ(cc-bar) = 7.1 ± 2.4(stat.) ± 1.4(syst.) µb/nucleon), some properties of D⁰ and D-bar⁰ were investigated. These include the atomic-weight dependence of the cross section on the target mass number (its A dependence); the differential cross sections dσ/dp_t² and dσ/dx_F; and the dependence of the parameter α on x_F, p_t², and p_lab. The experimental results are compared with the predictions of the FRITIOF7.02 program.

[en] Results obtained by measuring fluctuations of the number of neutral pions in the SERP-E-190 Experiment (Thermalization Project) upon irradiating a liquid-hydrogen target of the SVD-2 setup with a beam of 50-GeV protons are presented. A simulation of the detection of photons from the decay of neutral pions with the aid of an electromagnetic calorimeter revealed a linear relation between the number of detected photons and the mean number of neutral pions in an event. After the introduction of corrections for the loss of charged tracks because of a limited acceptance of the setup, trigger operation, and the efficiency of the data-treatment system, distributions of the number of neutral pions, N₀, were obtained for each value of the total number of particles in an event, N_tot = N_ch + N₀. The fluctuation parameter ω = D/〈N₀〉 was measured. In the region N_tot > 22, fluctuations of the number of neutral pions increase, which, within statistical models (GCE, CE, MCE), indicates that the system involving a large number of pions approaches the pion-condensate state. This effect was observed for the first time.

[en] Project Thermalization (Experiment SERP-E-190 at IHEP) is aimed to study the pp interactions at 50 GeV with large number of secondary particles. In this report the experimentally measured topological cross sections have been presented taking into account the detector response and procession effciency. These data are in good agreement with gluon dominance model. The comparison with other models is also made and shows no essential discrepancies.

[en] Hadron and nuclear interactions at high energies in the region of extreme multiplicities (much higher than mean multiplicities) are reviewed. Collective phenomena such as Bose-Einstein condensation, Cherenkov gluon radiation, clustering, and an excess yield of soft photons may manifest themselves in this region. The phenomenological gluon-dominance model developed for describing extreme multiplicities predicts the restrictions on their values and the type of hadronization mechanism and makes it possible to estimate thee size of the hadronization region. The status of the research within the Thermalization project at the U-70 accelerator of the Institute for High Energy Physics (IHEP, Protvino) is reported, and information about searches for new collective phenomena and about studies of known ones in the region of extreme multiplicities is given.

[en] The results of an analysis of data from the SERP-E-184 experiment devoted to studying mechanisms of the production of charmed particles in proton–nucleus interactions at 70 GeV and their decays are presented. The data in question were obtained upon irradiating the SVD-2 active target consisting of carbon, silicon, and lead plates with a beam of 70-GeV protons. A detailed simulation on the basis of the FRITIOF7.02 and GEANT3.21 code packages made it possible to optimize event-selection criteria and to calculate the detection efficiency for Λ_c"+ baryons. After selecting a signal from the threebody decay of a Λ_c"+ baryon, the inclusive cross section for its production at near-threshold energies, its lifetime, and the parameter of the A dependence of the cross section were found. The Λ_c"+ -baryon yields are tabulated along with data from other experiments and theoretical predictions.