The reaction A (pi,pipi) X on Ti and Fe nuclei has been studied at the energy E(pi) = 1.4 GeV. One of the final-state pions, moving forward with momentum > 0.7 GeV/c, is detected by a magnetic spectrometer. The second pion, emitted backward in the angular interval 120-degrees-150-degrees, is detected by the counters of a nonmagnetic hadron spectrometer. An anomalously large number of events corresponding to an interaction with the nucleus as a whole or with a cluster with mass considerably greater than that of an alpha particle are found at small energy transfer and at momentum transfer on the order of p(F). This interaction leaves the nucleus in a slightly excited state. These events may be interpreted as support for the hypothesis of nuclear critical opalescence. An alternative interpretation of the enhancement at small energy transfer might be the existence of a highly excited nuclear state (at 180 MeV) which decays through emission of a pi meson.

In the process of development of a measuring complex for the study of nuclear reactions at the Institute of Theoretical and Experimental Physics, the FOCUS apparatus was created for simultaneous investigation of the regions of target-nucleus fragmentation and impinging-particle fragmentation. The FOCUS apparatus is based on an MS-12 magnet and the elements of a nonmagnetic hadron spectrometer. The parameters of the apparatus and its calibration procedure are described.

The correlation functions of cumulative protons and also of protons and deuterons emitted at an angle theta = 120/sup 0/ are investigated and discussed as functions of their energies, separation angles, target--nucleus mass number, and the type and energy of the initial particle. Azimuthal correlations of cumulative protons are observed, which are stronger, the lighter is the nucleus.

Yields of protons and neutrons from various nuclei bombarded by 7.5-GeV/c protons are measured and discussed. Special attention is given to data obtained for the separated isotopes /sup 58/Ni, /sup 64/Ni, /sup 112/Sn, and /sup 124/Sn. It is shown that with increase of the neutron content of the isotope, the proton yields are practically unchanged while the neutron yields grow.

The shape of the region of production of cumulative particles has been studied by analysis of the distributions of pairs of cumulative protons emitted from Pb nuclei in the longitudinal and transverse components of the difference of their momenta. Indications are obtained that this region is nonspherical: The dimension which is longitudinal with respect to the direction of the incident particle is greater than the transverse dimension.

Correlations of cumulative baryons emitted from nuclei of Al, Cu, and Pb with small relative momenta are investigated. The nuclei were bombarded by protons with momentum 8.3 GeV/c. The secondary particles were recorded at angles 110--160/sup 0/ lab and had momenta 0.32--0.90 GeV/c. Information was obtained on the space-time characteristics of the region from which the cumulative particles are emitted.

The inclusive angular distributions for deep inelastic nuclear reactions are compared with the predictions of various models. A simple unified parametrization is proposed for all the invariant inclusive cross sections which have been studied.

Experimental data are reported on inclusive ..pi../sup -/ production at an angle of 62 mrad in the laboratory frame in proton--nucleus interactions at proton momenta of 3.95, 6.7, 8.8, and 9.7 GeV/c and on the inclusive production of ..pi../sup -/ mesons and protons at an angle of 188 mrad in proton--nucleus interactions at 9 GeV/c. The possibility of determining the cross sections for the interaction of ''young'' pions with the nucleons of the nucleus from the inclusive data is analyzed.

The reaction ..pi../sup -/A..-->..p/sub 1/p/sub 2/...pn+A'+ neutral particles has been studied in the nuclei C, Al, Cu, and Pb at a ..pi../sup -/-meson momentum of 3.7 GeV/c. It is shown that the spectra of protons emitted backwards in the lab in this reaction are similar to the inclusive spectra. Correlation of the protons has been studied. The shape of the proton spectrum at angles greater than 120/sup 0/ lab depends weakly on the total multiplicity of protons, the number of protons emitted backwards in the lab, and the momentum of the fast particles emitted forward. Indications are obtained that the size of the interaction region is of the order of the nuclear size.

Multiple production of hadrons in pA and ..pi../sup -/A interactions has been studied for the nuclei Be, C, Al, Cu, Cd, Pb, and U at momentum 7 GeV/c. Data are given on the differential multiplicities of protons and ..pi../sup -/ mesons, the topological cross sections, and two-particle correlations. The results are interpreted qualitatively in terms of fragmentation of the incident particle and target nucleus.

Multiple production of particles was investigated in inelastic proton-nuclear and pion-nuclear interactions at a momentum P=7 GeV/c for the nuclei Be, C, Al, Cu, Cd, Pb, and U. It was found that the distribution in the total multiplicity of the charged particles is described by the same universal function Psi (z) as for the pp interactions.

The construction of a solid-deuterium target 15 cm long is described and certain characteristics are given. The target operated for several months, and the liquid helium used as the coolant was added once or twice per week.