Test of QCD analytic predictions for the multiplicity ratio between gluon and quark jets

The OPAL Collaboration

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Gluon jets with about 39 GeV energy are identified in hadronic Z0 decays by tagging two jets in the same hemisphere of an event as quark jets. 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 rch. = 1.552 ± 0.041 (stat.) ± 0.061 (syst.) for the ratio of the mean charged particle multiplicity in gluon jets to that in light quark uds jets, where the uds jets are identified using an inclusive jet definition similar to that used for the gluon jets. Our result is in general agreement with the prediction of a recent analytic calculation which incorporates energy conservation into the parton shower branching processes, but is considerably smaller than analytic predictions which do not incorporate energy conservation.

Original languageEnglish
Pages (from-to)659-672
Number of pages14
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number3
StatePublished - 21 Nov 1996
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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