A Study of Parton Fragmentation in Hadronic Z0 Decays Using Lambda-Lambdabar Correlations

TL;DR

This paper investigates Lambda-Lambdabar baryon correlations in Z0 decays, testing fragmentation models and revealing short-range quantum number compensation, with JETSET providing the best but improvable fit.

Contribution

It provides the first detailed analysis of Lambda-Lambdabar correlations in 2- and 3-jet Z0 decays, testing and comparing fragmentation models against experimental data.

Findings

JETSET model best describes the data but needs parameter tuning.

MOPS and HERWIG models do not fit the data satisfactorily.

Short-range quantum number compensation is supported in di-lambda production.

Abstract

The correlated production of Lambda and Lambdabar baryons has been studied using 4.3 million multihadronic Zo decays recorded with the OPAL detector at LEP. Di-lambda pairs were investigated in the full data sample and for the first time also in 2-jet and 3-jet events selected with the k_t algorithm. The distributions of rapidity differences from correlated Lambda-Lambdabar pairs exhibit short-range, local correlations and prove to be a sensitive tool to test models, particularly for 2-jet events. The JETSET model describes the data best but some extra parameter tuning is needed to improve agreement with the experimental results in the rates and the rapidity spectra simultaneously. The recently developed modification of JETSET, the MOdified Popcorn Scenarium (MOPS), and also HERWIG do not give satisfactory results. This study of di-lambda production in 2- and 3-jet events supports the short-range compensation of quantum numbers.