We review status and perspectives of the search of the η-mesic nuclei at the synchrotron NUCLOTRON. This article present the results obtained at the spectrometer “SCAN” and the plans to study the interaction of eta-meson with nucleon and modification of the particle properties in the nuclear matter.

Nonstatistical fluctuations of particle production in relativistic collisions have been studied using the method of scaled factorial moments. Such fluctuations may be used to signal the formation of a quark-gluon plasma in the early stage of heavy ion interactions at high energies. The experimental data of Pb-208 nuclei at 158 A GeV/c taken with nuclear emulsion have been analysed. The dependences of intermittency parameter lambda(q) on the order of factorial moment q have been studied for O-16 and Pb-208 induced interactions.

Fe-, Kr- and Xe-induced heavy-ion reactions at ∼ 1 A GeV show factorization in the production cross-sections only for light fragments. Both "strong" and "weak" factorization are found for light fragments. The cross-sections of these fragments are described in detail within the prescription of cold breakup of spectator residues.

Angular distributions of spectator particles in dp and 4 Hep reactions in the region of a few GeV have been studied. Significant asymmetries of the spectator particle distributions have been observed for reactions where π -mesons are produced in the final state. Results of calculations in the framework of a spectator model taking into account the nuclear wave function, flux factor and the energy dependence of the NN elementary cross-sections, have been compared to experimental data. A good agreement has been observed for the fragments momenta, where the one-pole mechanism dominates.

. Using emulsion detector the collective flow signals in inelastic interactions of 84 Kr nuclei with Ag(Br) at 950 MeV/nucleon are studied. A transverse momentum analysis is performed to determine the reaction plane. The bounce-off of spectator fragments is observed. In azimuthal distributions relative to the reaction plane squeeze-out and side-splash of participants are seen.

The He-4 p--> H-3 pn pi(+) reaction channel has been investigated at an incident 4He momentum of 8.6 GeV/c in an exclusive approach. It has been shown that the reaction mainly proceeds via pp--> pn pi(+) interaction with (p pi(+)) from Delta(++), while triton is a spectator. The anisotropic angular distribution of the nucleons causes the splitting of ((3)Hn) invariant mass and leads to a natural separation of the interactions occuring either in proton or 4He vertices. Effects such as the shift of peak position in the (p pi(+)) invariant mass distribution have not been observed. [S0556-2813(98)07912-6].

The ${}^{4}\mathrm{He} \stackrel{\ensuremath{\rightarrow}}{p}{ }^{3}\mathrm{H} \mathrm{pn}{\ensuremath{\pi}}^{+}$ reaction channel has been investigated at an incident ${}^{4}\mathrm{He}$ momentum of $8.6 \mathrm{GeV}/c$ in an exclusive approach. It has been shown that the reaction mainly proceeds via $p\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{pn}{\ensuremath{\pi}}^{+}$ interaction with $(p{\ensuremath{\pi}}^{+})$ from ${\ensuremath{\Delta}}^{++},$ while triton is a spectator. The anisotropic angular distribution of the nucleons causes the splitting of ${(}^{3}\mathrm{H}n)$ invariant mass and leads to a natural separation of the interactions occuring either in proton or ${}^{4}\mathrm{He}$ vertices. Effects such as the shift of peak position in the $(p{\ensuremath{\pi}}^{+})$ invariant mass distribution have not been observed.

Emission of projectile and target fragments in inelastic interactions of Kr-84 nuclei with Ag (Br) at 0.95 GeV per nucleon is investigated with the aim of detecting collective flow. A transverse-momentum analysis is performed in the reaction plane. The bounce-off of projectile fragments is observed. This effect is found to become stronger with decreasing impact parameter.

Inelastic mechanisms of meson-free fragmentation of the He-4 nucleus are discussed. Spatial correlations between secondary particles and the slopes of the differential cross sections d sigma/dt are investigated. Final-state interactions are shown to play an important role in the formation of deuterons and fragments of the 4He nucleus through coalescence. In the reaction (4)Hep --> dppn, the observed strong increase in the ratio of the proton and neutron yields for emission angles close to 180 degrees is consistent with the assumption that the effect of an intermediate Delta isobar is significant.

Inelastic interactions induced by84Kr nuclei at 800–950 MeV/nucleon have been studied using a high angular resolution emulsion detector. Data on multiplicities of the produced particles, projectile and target fragments are shown. Comparisons with cascade calculations have been performed.

Data on the deuteron momentum, the Wilkin angle, and the 4-momentum transfer squared in the reactions (3)Hep --> dpp and (3)Hep --> pppn are obtained under experimental conditions permitting complete kinematic reconstruction. Final-state interactions leading to deuteron formation are shown to play a significant role.

Characteristics of reactions dp --> ppppi-, np --> pppi-, dp --> dppi+pi-, np --> dpi+pi-, dp --> dnpi+ at 1.7 GeV/c per nucleon have been studied. By comparison of dp and np interactions the different mechanisms in deuteron reactions were separated and it was shown that the quasi free nucleon-proton process is dominant. More unambiguous selection of spectators was demonstrated simultaneously. Their momenta distributions were well described by the known deuteron wave functions up to 0.4 GeV/c. It was shown that exotic effects at high momenta contribute in less than 3% of events.

4He-p collisions at two values of4He momenta 8.6 GeV/c and 13.6 GeV/c as well as the3He-p collisions at 13.5 GeV/c have been studies using the one-meter JINR hydrogen bubble chamber. Total, elastic, topological and reaction cross sections have been measured. The cross sections have been determined on a sample of minimum biased events.

4He-p collisions at two values of4He momenta-8·6 GeV/c and 13·6 GeV/c — have been studied using the one-metre JINR hydrogen bubble chamber. Total, elastic and topological cross sections have been measured. The results are in agreement with other published data. The elastic differential cross section was compared with the predictions of the Glauber model formalism.