We evaluate the strength of rapidity correlations as measured by bin-averaged multiplicity moments for hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for comparable c.m. energies √s ∼20 GeV. The strength of the correlation decreases rapidly with increasing complexity of the reaction. Although statistically significant cumulant moments, ${\mathit{K}}_2$, ${\mathit{K}}_3$, and ${\mathit{K}}_4$ are found in hadron-hadron (NA22) collisions, higher moments are strongly suppressed (except for ${\mathit{K}}_3$ in KLM Collaboration proton-emulsion data) when nuclei are involved. When ordinary factorial moments are decomposed into cumulant moments, the former are seen to be dominated by combinatoric contributions of the (experimentally determined) cumulant moment ${\mathit{K}}_2$. Hence rapidity fluctuations and intermittent effects are significantly decreased by the use of nuclei as targets and/or projectiles. This result could possibly be reversed at the onset (at higher energy) of a new phase having strong fluctuations, for example, the long-sought quark-gluon plasma.

• Received 13 May 1991

DOI:https://doi.org/10.1103/PhysRevC.44.1629