Two-particle angular correlations in $e^+ e^-$ collisions to hadronic final states in two reference coordinates at Belle

TL;DR

This paper analyzes two-particle angular correlations in electron-positron collisions at Belle, comparing coordinate systems and providing new measurements at energies around the Upsilon(4S) resonance, enhancing understanding of correlation structures.

Contribution

It introduces the use of the event thrust axis as a coordinate system for correlation analysis in $e^+ e^-$ collisions and presents the first such measurement at the Upsilon(4S) energy.

Findings

Correlation structures vary with charged-particle multiplicity.

Event thrust axis offers a useful perspective for correlation interpretation.

Qualitative agreement with Monte Carlo simulations is observed.

Abstract

We present the analysis of two-particle angular correlations using coordinate systems defined with the conventional beam axis and the event thrust axis, and propose the latter to be a useful representation for the correlation structure interpretation in the $e^+ e^-$ collision system. The $e^+ e^-$ collisions to hadronic final states at center-of-mass energies of $\sqrt{s} = 10.52$ GeV and $10.58$ GeV are recorded by the Belle detector at KEKB. In this paper, results on the first dataset are supplementary to the previous Belle publication arXiv:2201.01694 while the latter one is the first two-particle correlation measurement at a collision energy on the $\Upsilon(4S)$ resonance and sensitive to its decay products. Measurements are reported as a function of the charged-particle multiplicity. Finally, a qualitative understanding of the correlation structure is discussed using a combination of Monte Carlo simulations and experimental data.