Correlation between multiplicities in windows separated in azimuth and rapidity

摘要

The forward-backward (FB) multiplicity correlations in two windows separated in rapidity and azimuth are analyzed in the framework of the model with independent identical sources (strings). Along with the short-range (SR) contribution, originating from the correlation between particles produced by a single string, the long-range (LR) contribution, originating from the fluctuation in the number of strings, is taken into account. The connection of the FB multiplicity correlation coefficient with the two-particle correlation function is traced. The dependencies of the correlation coefficient on the rapidity and azimuthal acceptance of the windows and on the corresponding gaps between them are studied. It is shown that the analysis of these dependencies enables to separate the contributions of two above mechanisms. The comparison of the results with the preliminary experimental data of ALICE shows the strong increase of the LR correlation with the growth of energy from 0.9 to 7 TeV, whereas the contribution of the SR correlations, characterizing the properties of a single source, remains practically the same. In the frame work of the model it corresponds to a three fold increase of the event-by-event fluctuations in the number of emitting sources (strings) with this growth of energy.