Search

Azimuthal correlations between the same type of particles (protons or pions) in the target fragmentation region was studied in d, He, C+C, Ta (4.2A GeV/c, C+Ne, Cu (4.5A GeV/c) and p+C, Ta (10 GeV/c) interactions. The data were obtained from the SKM-200-GIBS streamer chamber and from the Propane Bubble Chamber (PBL-500) systems utilized at JINR. Study of multiparticle azimuthal correlations offers unique information about space-time evolution of the interactions. Azimuthal correlations were investigated by using correlation function $ C(\Delta\phi) = \mathrm{d} N/\mathrm{d} (\Delta\phi)$ , where $ \Delta\phi$ represents the angle between the sums of transverse momenta vectors for particles emitted in the forward and backward hemispheres. For protons “back-to-back” (“negative”) azimuthal correlations were observed in the above-mentioned interactions. The absolute values of the correlation coefficient $ \vert\xi\vert$ --the slope parameter of $ C(\Delta\phi)$, strongly depend on the mass number of the target ($ A_{T}$) nuclei in the nucleon-nucleus and nucleus-nucleus collisions. Namely, $ \vert\xi\vert$ decreases with increase of $ A_T$ in p+C and p+Ta collisions, while $ \vert\xi\vert$ initially decreases from d+C to C+Ne and then almost does not change with increase of $ A_P$, $ A_T$ in (d+He)Ta, C+Cu and C+Ta collisions. For pions “back-to-back” correlations were obtained for light targets (C, Ne), and “side-by-side” (“positive”) correlations for heavy targets (Cu, Ta). The $ \vert\xi\vert$ insignificantly changes with increase of the momenta per nucleon and almost does not change with increase of $ A_P$ and $ A_T$. Models used for description of the data, the Ultra relativistic Quantum Molecular Dynamic (UrQMD) and Quark-Gluon String Model (QGSM), satisfactorily describe the obtained experimental results.

In the collisions of 4.1 A GeV/c22Ne with AgBr emulsion nuclei, events exhibiting projectile and target fragmentation have been selected. The characteristics of these events are not reproduced by the cascade-evaporation model. The angular distributions and correlation between projectile and target fragments have shown the “bounce off” of the former and the “side splash” of the latter.

A study of general characteristics of events accompanied by the emission of fast hadrons into the backward hemisphere in the laboratory system has been carried out for interactions of protons and alpha-particles with nuclei at a momentum of 4.5 GeV/c per nucleon. A unified description of multiplicity distributions of these hadrons for interactions with light and heavy emulsion nuclei has been found. It is shown that the selection of events with fast hadrons flying backward leads to a complete destruction of light nuclei and a strong desintegration of heavy nuclei. A comparison with the cascade-evaporation model, carried out for αA interactions, shows that the model overestimates the multiplication of secondary particles, particularly for light target nuclei.

Average multiplicity of protons fromp, d, α andC interactions with carbon at 4.2 GeV/c/ N is shown to increase with the mass number of incident nucleus. ThisA dependence is stronger for fast protons than for the slow ones. Angular and momentum distributions are described by the Dubna Cascade Model. Some discrepancy is observed in the high momentum part of the distributions.

Correlations between secondary protons with small relative momenta have been studied in interactions of various light nuclei with the carbon target at 4.2 GeV/c per incident nucleon with the aim to determine the radius of the proton emission region. This radius is found to decrease with increasing momentum and transverse momentum of the proton pair, but it does not show any dependence on the mass of the projectile nucleus.

New experimental data on proton-nucleus interactions in emulsion at primary momentum 4.5 GeV/c are presented and discussed. The data are systematically compared with predictions of the cascade-evaporation model. The directions of development of the cascade-evaporation model in a region of incident momenta are considered, and some suggestions are made for giving it more precision.