Introduction

The goal of the analysis is to probe the perturbative QCD at the limits of its applicability by studying such inherently soft processes as jet fragmentation. The plots presented below compare the inclusive momentum spectra of charged particles in jets for variety of dijet masses and openning angles with the theoretical calculations carried out in the framework of the Modified Leading Log Approximation (MLLA). The data reproduces the MLLA predictions and, therefore, confirms that the domain of perturbative QCD may be expanded down to the cut-off scale Qeff of the order of LambdaQCD. Fits of different distributions consistently give Qeff=230+/-20 MeV.

Blessed plots

• inclusive momentum distribution of charged tracks within an opening angle 0.466 for events with a dijet mass around Mjj=390 GeV/c2 (x=p/Ejet in the dijet c.m. system). Fit is the MLLA Limiting Spectrum for gluon jets.
• Distributions for different dijet masses at a fixed opening angle. Fits are done according to the MLLA Limiting Spectrum.
• Evolution of inclusive momentum distribution with opening angle varying from 0.168 to 0.466. Fits are done according to the MLLA Limiting Spectrum.
• Peak position of the distributions vs (dijet mass)x(opening angle). Fit is the MLLA prediction. TASSO/OPAL/ALEPH data are superimposed for comparison.

Last updated June 6, 1996.