G. Alexander et al., TEST OF QCD ANALYTIC PREDICTIONS FOR THE MULTIPLICITY RATIO BETWEEN GLUON AND QUARK JETS, Physics letters. Section B, 388(3), 1996, pp. 659-672
Gluon jets with about 39 GeV energy are identified in hadronic Z(0) de
cays by tagging two jets in the same hemisphere of an event as quark j
ets. Identifying the gluon jet to be all the particles observed in the
hemisphere opposite to that containing the two tagged jets yields an
inclusive gluon jet definition corresponding to that used in analytic
calculations, allowing the first direct test of those calculations. In
particular, this jet definition yields results which are only weakly
dependent on a jet finding algorithm. We find r(ch)=1.552+/-0.041 (sta
t.)+/-0.061 (syst.) for the ratio of the mean charged particle multipl
icity in gluon jets to that in light quark uds jets, where the uds jet
s are identified using an inclusive jet definition similar to that use
d for the gluon jets. Our result is in general agreement with the pred
iction of a recent analytic calculation which incorporates energy cons
ervation into the parton shower branching processes, but is considerab
ly smaller than analytic predictions which do not incorporate energy c
onservation.