DOI 10.1007/s100529800885
Investigation of the splitting of quark and gluon jets
DELPHI Collaboration
P.Abreu21 - et al.
21 LIP, IST, FCUL - Av. Elias Garcia, 14-1o, 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 CA/CF.
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 . 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.
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