Measurement of Two-Particle Correlations of Hadrons in $e^{+}e^{-}$ Collisions at Belle

TL;DR

This paper reports on two-particle angular correlation measurements in high-multiplicity electron-positron collisions at 10.52 GeV using Belle data, finding no significant collective behavior and providing constraints for phenomenological models.

Contribution

First measurement of two-particle correlations in $e^+e^-$ collisions at this energy, analyzing both beam and thrust axes, and comparing results to event generator predictions.

Findings

No significant anisotropic collective behavior observed.

Near-side jet correlations are absent in the thrust axis analysis.

Results provide new constraints for low-energy phenomenological models.

Abstract

The measurement of two-particle angular correlation functions in high-multiplicity $e^+e^-$ collisions at $\sqrt{s}=10.52$ GeV is reported. In this study, the $89.5~{\text{fb}}^{-1}$ of hadronic $e^+e^-$ annihilation data collected by the Belle detector at KEKB are used. Two-particle angular correlation functions are measured in the full relative azimuthal angle ($\Delta \phi$) and three units of pseudorapidity ($\Delta \eta$), defined by either the electron beam axis or the event-shape thrust axis, and are studied as a function of charged-particle multiplicity. The measurement in the thrust axis analysis, with mostly outgoing quark pairs determining the reference axis, is sensitive to the region of additional soft gluon emissions. No significant anisotropic collective behavior is observed with either coordinate analyses. Near-side jet correlations appear to be absent in the thrust axis analysis. The measurements are compared to predictions from various event generators and are expected to provide new constraints to the phenomenological models in the low-energy regime.