Genuine Correlations of Like-Sign Particles in Hadronic Z0 Decays

TL;DR

This study investigates genuine correlations among like-sign hadrons in Z0 decays using high-statistics data, revealing strong positive correlations likely influenced by Bose-Einstein effects and evaluating simulation models.

Contribution

It provides a detailed analysis of like-sign particle correlations in Z0 decays using factorial cumulants, highlighting the role of Bose-Einstein correlations and testing Monte Carlo simulations.

Findings

Strong positive genuine correlations among like-sign hadrons.

Cumulants increase with decreasing phase space size and saturate in one dimension.

Monte Carlo models with Bose-Einstein effects reproduce measured correlations.

Abstract

Correlations among hadrons with the same electric charge produced in Z0 decays are studied using the high statistics data collected from 1991 through 1995 with the OPAL detector at LEP. Normalized factorial cumulants up to fourth order are used to measure genuine particle correlations as a function of the size of phase space domains in rapidity, azimuthal angle and transverse momentum. Both all-charge and like-sign particle combinations show strong positive genuine correlations. One-dimensional cumulants initially increase rapidly with decreasing size of the phase space cells but saturate quickly. In contrast, cumulants in two- and three-dimensional domains continue to increase. The strong rise of the cumulants for all-charge multiplets is increasingly driven by that of like-sign multiplets. This points to the likely influence of Bose-Einstein correlations. Some of the recently proposed algorithms to simulate Bose-Einstein effects, implemented in the Monte Carlo model PYTHIA, are found to reproduce reasonably well the measured second- and higher-order correlations between particles with the same charge as well as those in all-charge particle multiplets.