Multiparticle correlations and intermittency in high energy collisions

In this work the analysis of the intermittency signal observed in high energy experi- ments is done using multiparticle distributions and correlation functions. The effect of the dimensional projection of the multiparticle distributions on one or two-dimensional subspace is discussed. The structure of the multiparticle cumulants is analyzed for the DELPHI e + e~ annihilation data. The language of the self-similar distribution func- tions, which is used in this work, is shown to be largely equivalent to the well known a-model. In the case of the ultrarelativistic nuclear collisions, where the Monte-Carlo simulations fail to reproduce the data, we argue that the observed intermittency pattern is a signal of some nonlinear effect beyond the simple superposition of nucleon-nucleon collisions. The model of spatiotemporal intermittency is discussed in details and is shown to reproduce qualitatively the dependence of the intermittency strength on the target and projectile nuclei. Similar effects are also observed in the statistical systems undergoing a higher order phase transition. We study in particular a 1-dimensional (ID) cellular-automaton (CA) and a ID forest-fire model. On the example of the noncritical ID Ising model we illustrate the difficulties of the scaled factorial moment (SFM) method in extracting genuine scaling behaviour. The problem of the finite-size effect in connection to the dimensional projection can be easily exemplified in the case of the 2D critical system with conformai symmetry. All these studies could serve as tools to test the sensibility of the SFM method as used in the analysis of the high energy production.