The observation of collective effects in central CNe and CCu collisions at a momentum of 4.5 GeV/c per nucleon

The transverse momentum technique is used to analyse charged-particle exclusive data in the central CNe and CCu interactions at a momentum of 4.5 GeV/c per nucleon. The results are presented in terms of the mean transverse momentum per nucleon projected onto the estimated reaction plane 〈P′x(Y)′ as a function of the rapidity Y in the laboratory system. The observed dependence shows the typical S-shape behaviour reflecting the presence of flow effects. The value of flow F is obtained that increases with the atomic number of the target. The Monte Carlo cascade Quark Gluon String Model (QGSM) is used for the comparison with the experimental data. The QGSM reproduces the spectra and the mean kinematical characteristics of the protons (〈Y〉…〈Np〉) but underestimates their transverse flow.