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Abstract.The results of E-190 experiment (project Thermalization) with 50 GeV proton beam irradiation of SVD-2 setup are presented. MC simulation has shown the linear dependence of number of photons detected in electromagnetic calorimeter and the average number of neutral pions. Multiplicity distribution of neutral pion, N 0 , for total number of particles in the event, N tot = N ch + N 0 , are obtained with corrections on the setup acceptance, triggering and efficiency of the event reconstruction. The scaled variance of neutral pion fluctuations, ω = D/ < N 0 >, versus total multiplicity is measured. The fluctuations increase at N tot > 18. According to quantum statistics models this behavior can indicate a pion condensate formation in the high pion multiplicity system. This effect has been observed for the first time.

The stages of development and the current status of the versatile "Spectrometer with a Vertex Detector" setup designed for physics experiments at the U 70 accelerator of the Institute for High Energy Physics (Protvino) is described. The main detectors of the setup are the vertex detector based on silicon microstrip detectors, the wide aperture magnetic spectrometer based on multiwire proportional chambers, and the lead glass hodoscope γ detector. In the setup, there is a fast two level trigger system for selecting required particle interactions. The key characteristics of the setup systems are presented, and the physical results obtained on it are briefly listed. * To study the dependence of the cross sections on the atomic number of the nucleus, a passive target-a lead foil 220 µm thick-is located at a point with Z coordinate of +8 mm, and the passive target-a carbon plate 500 µm thick-is located at a point with Z coordinate of +16 mm.

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