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Multiplicity distributions of gluon and quark jets and a test of QCD analytic calculations

✍ Scribed by J.William Gary


Publisher
Elsevier Science
Year
1999
Tongue
English
Weight
479 KB
Volume
71
Category
Article
ISSN
0920-5632

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✦ Synopsis


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 mean and first few higher moments of the gluon jet charged particle multiplicity distribution are compared to the analogous results found for light quark (uds) jets, also defined inclusively. Large differences are observed between the mean, skew and curtosis values of the gluon and quark jets, but not between their dispersions. The cumulant factorial moments of the distributions are also measured, and are used to test the predictions of QCD analytic calculations. A calculation which includes nextto-next-to-leading order corrections and energy conservation is observed to provide a much improved description of the separated gluon and quark jet cumulant moments compared to a next-to-leading order calculation without energy conservation. There is good quantitative agreement between the data and calculations for the ratios of the cumulant moments between gluon and quark jets. The data sample used is the LEP-1 sample of the OPAL experiment at LEP.


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