Multiplicity distributions of
gluon and quark jets and tests
of
QCD analytic predictions
OPAL Collaboration, K. Ackerstaff8 et al.
8 CERN, European Organisation for Particle Physics, CH-1211 Geneva 23, Switzerland
Received: 1 August 1997
Abstract
Gluon jets are identified in e+e- hadronic
annihilation events by tagging two quark jets in
the same hemisphere of an event.
The gluon jet is defined inclusively
as all the particles in the opposite hemisphere.
Gluon jets defined in this manner
have a close correspondence to gluon jets as
they are defined for analytic calculations,
and are almost independent of a
jet finding algorithm.
The charged particle multiplicity distribution
of the gluon jets is presented,
and is analyzed for its mean, dispersion, skew,
and curtosis values,
and for its factorial and cumulant moments.
The results are compared to the analogous
results found for a sample of light quark (uds) jets,
also defined inclusively.
We observe differences between the mean,
skew and curtosis values of gluon and quark jets,
but not between their dispersions.
The cumulant moment results are compared to the
predictions of QCD analytic calculations.
A calculation which includes
next-to-next-to-leading order corrections
and energy conservation
is observed to provide a much improved description
of the data compared to a next-to-leading order
calculation without energy conservation.
There is agreement between the data and
calculations for the ratios of the cumulant moments
between gluon and quark jets.
Copyright Springer-Verlag
