Scaling violations of quark and gluon jet fragmentation functions in e+e- annihilations at sqrt(s) = 91.2 and 183-209 GeV

TL;DR

This study measures quark and gluon jet fragmentation functions at different energies in e+e- collisions, observing stronger scaling violations in gluon jets and comparing results with theoretical models and simulations.

Contribution

It provides detailed measurements of fragmentation functions at multiple energies and compares them with theoretical predictions and Monte Carlo models, highlighting discrepancies especially for gluon and b jets.

Findings

Scaling violations are stronger for gluon jets than quark jets.

Monte Carlo models agree well with data, but theoretical NLO calculations do not fully describe the results.

Fragmentation functions are consistent with previous experiments and show energy dependence.

Abstract

Flavour inclusive, udsc and b fragmentation functions in unbiased jets, and flavour inclusive, udsc, b and gluon fragmentation functions in biased jets are measured in e+e- annihilations from data collected at centre-of-mass energies of 91.2, and 183-209 GeV with the OPAL detector at LEP. The unbiased jets are defined by hemispheres of inclusive hadronic events, while the biased jet measurements are based on three-jet events selected with jet algorithms. Several methods are employed to extract the fragmentation functions over a wide range of scales. Possible biases are studied in the results are obtained. The fragmentation functions are compared to results from lower energy e+e- experiments and with earlier LEP measurements and are found to be consistent. Scaling violations are observed and are found to be stronger for the fragmentation functions of gluon jets than for those of quarks. The measured fragmentation functions are compared to three recent theoretical next-to-leading order calculations and to the predictions of three Monte Carlo event generators. While the Monte Carlo models are in good agreement with the data, the theoretical predictions fail to describe the full set of results, in particular the b and gluon jet measurements.