Multiplicity fluctuations and correlations in $^{16}$O–AgBr collisions at AGS and SPS energies

Abstract

Dependence of multiplicity distributions (MDs) and their moments $\sigma$, C$_2$, $\gamma _2$ and f$_2$ on the width and position of pseudorapidity($\eta$) windows are examined by analyzing the experimental data on the interactions of AgBr nuclei with $^{16}$O beam at 14.6A GeV from AGS, BNL and at 60A and 200A GeV from SPS, CERN. The findings indicate the presence of correlations and fluctuations of dynamical origin. The results also suggest that these features of the data, if looked into using the data of limited centrality, where geometrical fluctuations due to impact parameter variations are under control, might lead to some interesting conclusions on the strength and length of the correlations present. The study of intensive variable–the scaled variance ($\omega$) in two pseudorapidity windows of varying widths, one placed in forward and the other in the backward $\eta$ regions, suggests that MDs in the backward $\eta$ region are rather non smooth and wider as compared to that in the forward $\eta$ region and the correlations present are of short range in nature. The ranges of the correlations are, however, observed to increase with increasing beam energy. The results based on the experimental data are nicely supported by AMPT model. URQMD model, however, predicts somewhat wider MDs as compared to the data.