The European Physical Journal C

ISSN: 1434-6044 (printed version)
ISSN: 1434-6052 (electronic version)

Table of Contents

Abstract Volume 4 Issue 1 (1998) pp 1-17
DOI 10.1007/s100529800885

experimental physics:
Investigation of the splitting of quark and gluon jets

DELPHI Collaboration , P. Abreu et al. (21)

(21) LIP, IST, FCUL - Av. Elias Garcia, 14-1°, PT-1000 Lisboa Codex, Portugal

Received: 18 February 1998 / Published online: 24 April 1998

Abstract. The splitting processes in identified quark and gluon jets are investigated using longitudinal and transverse observables. The jets are selected from symmetric three-jet events measured in Z decays with the Delphi detector in 1991-1994. Gluon jets are identified using heavy quark anti-tagging. Scaling violations in identified gluon jets are observed for the first time. The scale energy dependence of the gluon fragmentation function is found to be about two times larger than for the corresponding quark jets, consistent with the QCD expectation $C_A/C_F$. The primary splitting of gluons and quarks into subjets agrees with fragmentation models and, for specific regions of the jet resolution $y$, with NLLA calculations. The maximum of the ratio of the primary subjet splittings in quark and gluon jets is $2.77\pm0.11\pm0.10$. Due to non-perturbative effects, the data are below the expectation at small $y$. The transition from the perturbative to the non-perturbative domain appears at smaller $y$ for quark jets than for gluon jets. Combined with the observed behaviour of the higher rank splittings, this explains the relatively small multiplicity ratio between gluon and quark jets.

Article in PDF-Format
Article in (gzipped) PS-Format

Online publication: June 10, 1998
LINK Helpdesk
© Springer-Verlag Berlin Heidelberg 1998