Transition to the region of central collisions

The experimental results on the behaviour of the characteristics of secondary particles depending on the disintegration degree of nuclei are used to determine the region of central collisions. It was therefore possible that : - the correlation between the prosesses of total disintegration of nuclei and the central collisions of nuclei had been shown; - the existence of the regime change points in the behaviour of the considered characteristics of secondary particles depending on the disintegration degree of nuclei had been observed in the other earlier experiments as well. The number of all protons in 12CC-interactions at the momentum of 4.2 A GeV/c obtained from the 2-m propane bubble chamber exposed at the Dubna machine is considered as a disintegration degree of nuclei. The experimental results demonstrate that there are cases corresponding to the critical phenomena among the events with the central collisions of nuclei. For 12CC-interaction the behaviour of the number of the events, depending on Q also depends on the number of fragments and has a two-steps form. This result could be explained by the existence of nuclear clusters. The experimental results on the relation between the number of events, the angular distributions of protons and full number of protons are presented for 12CC-interactions at the momentum of 4.2 A GeV/c. The influence of nuclear fragmentation process on the results is also considered. The obtained results confirm the assumption that there exist the critical phenomena among the central collisions and it is necessary to use a percolation approach for the full description of the central collisions.