https://doi.org/10.1007/s100520200926
Experimental physics
Particle multiplicity of unbiased gluon jets from e+e− three-jet events
Dipartimento di Fisica dell’ Università di Bologna and INFN, 40126, Bologna, Italy
Received:
25
October
2001
Revised:
20
January
2002
Published online:
5
April
2002
The charged particle multiplicities of two- and three-jet events from the reaction e
e
Z
are measured for Z
decays to light quark (uds) flavors. Using recent theoretical expressions to account for biases from event selection, results corresponding to unbiased gluon jets are extracted over a range of jet energies from about 11 to 30 GeV. We find consistency between these results and direct measurements of unbiased gluon jet multiplicity from 
and Z decays. The unbiased gluon jet data including the direct measurements are compared to corresponding results for quark jets. We perform fits based on analytic expressions for particle multiplicity in jets to determine the ratio 
of multiplicities between gluon and quark jets as a function of energy. We also determine the ratio of slopes, 
, and of curvatures, 
, where y specifies the energy scale. At 30 GeV, we find 
and 
, where the uncertainties are the statistical and systematic terms added in quadrature. These results are in general agreement with theoretical predictions. In addition, we use the measurements of the energy dependence of 
and 
to determine an effective value of the ratio of QCD color factors, 
. Our result, 
(total), is consistent with the QCD value of 2.25.
© Springer-Verlag Berlin Heidelberg / Società Italiana di Fisica, 2002
