A novel method to study fluctuations in distributions of reaction products has been applied to investigate the process of chemical and thermal equilibration of nuclear matter in Ru+Ru reaction at 1.69 A GeV. The analysed data were obtained with the FOPI detector. Nontrivial fluctuations of the chemical composition and of transverse momenta, and their dependence on centrality were studied. Fluctuations of pion multiplicity were found to decrease with increasing centrality. This kind of dependence is less evident in the case of proton transversal momentum fluctuations.

PACS numbers: 24.60.Ky, 25.75.Ld