# Measurements of two-particle correlations in $e^+e^-$ collisions at 91 GeV with ALEPH archived data

## TL;DR

This study analyzes two-particle angular correlations in electron-positron collisions at 91 GeV using archived ALEPH data, finding no significant long-range correlations and providing insights into hadronization models.

## Contribution

First measurement of two-particle correlations in $e^+e^-$ collisions at 91 GeV with detailed analysis, comparing data to event generators and serving as a baseline for other collision systems.

## Key findings

- No significant long-range correlations observed.
- Better agreement with PYTHIA v6.1 than HERWIG v7.1.5.
- Provides reference for correlations in other collision types.

## Abstract

Measurements of two-particle angular correlations of charged particles emitted in hadronic $Z$ decays are presented. The archived $e^+e^-$ annihilation data at a center-of-mass energy of 91 GeV were collected with the ALEPH detector at LEP between 1992 and 1995. The correlation functions are measured over a broad range of pseudorapidity and full azimuth as a function of charged particle multiplicity. No significant long-range correlation is observed in either the lab coordinate analysis or the thrust coordinate analysis, where the latter is sensitive to a medium expanding transverse to the color string between the outgoing $q\bar{q}$ pair from $Z$ boson decays. The associated yield distributions in both analyses are in better agreement with the prediction from the PYTHIA v6.1 event generator than from HERWIG v7.1.5. They provide new insights to showering and hadronization modeling. These results serve as an important reference to the observed long-range correlation in proton-proton, proton-nucleus, and nucleus-nucleus collisions.