A trigger of events with a high multiplicity of charged particles at the SVD-2 setup

The Thermalization project is currently under way on the extracted proton beam of the U-70 accelerator at the Institute for High Energy Physics. The main goal of this experiment is to study the collective behavior of secondary particles produced in a multiparticle pp interaction at beam energy E = 50–70 GeV. The region of high charged-particle multiplicities n ch ≥ 10 is investigated. In this region, a significant portion of energy in the center-of-mass system is dissipated on production of secondary particles, which results in formation of a hadronic system. At the initial instant of evolution, the density of this system is high, which may be responsible for the collective behavior of the secondary particles. The investigations are performed at the SVD-2 wide-aperture magnetic spectrometer. A multichannel trigger scintillation hodoscope used to select rare events with a large number of charged particles exceeding the predetermined value is described. The main flow of low-multiplicity events is suppressed by the trigger system by a factor of ∼10 2 .