Two-particle azimuthal correlations in $e^+e^-$ collisions at 91--209 GeV with archived ALEPH data at LEP-2

• Main Authors: Lee, Yen-Jie, Chen, Yu-Chen, Chen, Yi, Chang, Paoti, Maggi, Marcello
• Format: Journal Article
• Language: English
• Published: 21-11-2022
• Subjects: Physics - High Energy Physics - Experiment; Physics - Nuclear Experiment
• DOI: 10.48550/arxiv.2211.11995

We present the first measurement of two-particle angular correlations of
charged particles produced in $e^+e^-$ annihilation up to $\sqrt{s}=$ 209 GeV.
This analysis utilized the archived hadronic $e^+e^-$ data at center-of-mass
energy between 91 and 209 GeV collected with the ALEPH detector at LEP between
1992 and 2000. The angular correlation functions are measured over a broad
range of pseudorapidity and full azimuth as a function of charged particle
multiplicity for the first time with LEP-2 data. At 91 GeV, no significant
long-range correlation is observed in either the beam 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 the Z boson decays. Results with $e^+e^-$ data at higher collision energy
than 91 GeV, providing higher event multiplicity reach up to around 50, are
presented for the first time. The thrust axis analysis shows a long-range
near-side excess in the two-particle correlation function. We performed Fourier
series decomposition of the two-particle correlation functions. In high
multiplicity events with more than 50 particles, the extracted Fourier
coefficients $v_2$ and $v_3$ magnitudes in data are larger than the MC
reference.