The many sources effect on the genuine multihadron correlations

Abstract

Here we report on a study aimed to explore the dependence of the genuine multiparticle correlations on the number of sources while the influence of other possible factors affecting the multihadron production is avoided. The analysis utilised the normalised cumulants, calculated in three-dimensional phase space, of the reaction e+e- -> Z -> hadrons using a large Monte Carlo event sample. The multi-sources reactions were simulated by overlaying a few independent single e+e- annihilation events. It was found that as the number of sources S increases, the cumulants do not change significantly their structure, but those of an order q>2 (i.e. more than 2 pions) decrease fast in their magnitude. This reduction can be understood in termsof combinatorial considerations of source mixing which dilutes the correlations by a factor of about 1/S^{q-1} which can also serve as a method to estimated the number of sources. This expected suppression is well reproduced by recent cumulant measurements in hadron and nucleus induced reactions both in one (rapidity) and two (rapidity vs. azimuthal angle) dimensions. The diminishing genuine correlations effect should also appear in other dynamical correlations like the Bose-Einstein in e+e- -> W+W- -> hadrons and in nucleus-nucleus reactions.