First results on measuring polarization in π - p →π°n reaction at 40 GeV/c are presented for the 4-momentum transfer range from 0.05 up to 0.4 (GeV/c)2. The experiment was carried out at the IHEP 70 GeV accelerator on a polarized proton target. Polarization in this reaction was earlier studied at incident momentum below 11.2 GeV/c/1–4/. Comparison of the present data with the previous ones allows us to see the polarization effect decreases with energy growth.

The cross sections for the production of ..pi../sup + -/ and K/sup + -/ mesons, protons, and antiprotons have been measured as a function of the mass number A of the target nucleus. The measurements were carried out at an angle of 90/sup 0/ in the c.m. system of the two nucleons for transverse momenta p/sub perpendicular/ between 0.5 and 2.5 GeV/c in collisions of protons with C, Al, Cu, Sn, and Pb nuclei at 70 GeV. Data are reported on the particle-yield ratios K/sup +//..pi../sup +/, K/sup -//..pi../sup -/, p/..pi../sup +/, and p-bar/..pi../sup -/ for these nuclei. These ratios are studied as a function of A. The results are compared with data at higher energies.

The methods to measure muon flux distributions in the muon filter of the IHEP neutrino beam are described. The construction and characteristics of the ionization chambers used as muon detectors are given. The detectors allow one to measure the muon fluxes with density from ⪆ 107 down to ∼102 muons/cm2 at ∼3 μs pulse duration. The system provides both monitoring of the neutrino beam and measuring of the total muon fluxes for neutrino spectrum reconstruction. The detector sensitivity was constant within the limits of 2–3% during a one-year period of operation in the neutrino beam.

The neutrino channel of the accelerator of the Institute of High-Energy Physics is described. The general characteristics of the systems for producing the neutrino beam and the properties of the neutrino and antineutrino beams are described. This paper is an introduction to a series of papers on this neutrino channel.