How Good are Present Analytical QCD-Predictions on Fluctuations in Angular Intervals ?

TL;DR

This paper evaluates the accuracy of current analytical QCD predictions on particle fluctuations and correlations in jet cones across various experiments, highlighting discrepancies and the importance of energy-momentum conservation.

Contribution

It compares experimental data with analytical QCD calculations, revealing the need to incorporate full energy-momentum conservation for better predictions.

Findings

Differential correlation functions deviate significantly from predictions.

Globally normalized correlation functions align well with data.

Emphasizes the importance of including energy-momentum conservation in models.

Abstract

Results on two-particle angular correlations in jet cones and on multiplicity fluctuations in one- and two- dimensional angular intervals, delivered by three experiments (DELPHI, L3 and ZEUS, at $\sqrt{s}$ from few to 183 GeV) are compared to present existing analytical QCD calculations, using the LPHD hypothesis. Two different types of functions have been tested. While the differentially normalized correlation functions show substantial deviations from the predictions, a globally normalized correlation function agrees surprisingly well. The role of the QCD parameters $\alpha_s$, $\Lambda$ and $n_f$ is discussed. The necessity to include full energy-momentum conservation into the analytical calculations is stressed.