Long-range particle correlations and wavelets

The problem of long-range correlations of particles produced in high-energy collisions is discussed. Long-range correlations may involve large groups of particles, as exemplified by the ring-like and elliptic flow patterns of individual high-multiplicity events in the polar and azimuthal angle planes. To identify such structures, a wavelet-analysis technique has been proposed and applied to some central lead-lead collisions at an energy of 158 GeV per nucleon. In the present paper, previous attempts at obtaining long-range correlations are discussed and recent wavelet-analysis results for high energy nucleus-nucleus interactions are reviewed.