Analysis of Multi - Jet Final States in $e^+ e^-$ Annihilation

Data accumulated by the TASSO detector across the whole range of energies spanned at PETRA, 12⩽ s ⩽46.8 GeV , have been analysed in terms of cluster algorithms. Using parameters optimised at 35 GeV CM energy, three perturbative QCD+fragmentation models were compared with the data. The O( α s 2 ) model gives too few 4,5- cluster events, implying that higher order QCD contributions are required to describe the data. The parton cascade model, incorporating many orders in perturbation theory, gives a better description of the rates of ⩾ 4 clusters, but shows a lack of hard gluon emission by giving too few 3-, and too many 2-cluster events. When hard gluon emission is taken into account, by the cascade model incorporating the O( α s ) matrix element, all cluster rates are reproduced well. All the models describe the trend of the evolution of the cluster rates between 〈 s 〉 = 14 and 43.8 GeV. We find that the rate of 3-jet events seen in the data decreases as s increases in a manner consistent with the Q 2 dependence of α s as predicted by QCD.

ELECTRON POSITRON: COLLIDING BEAMS
COLLIDING BEAMS: ELECTRON POSITRON
ELECTRON POSITRON: ANNIHILATION
ANNIHILATION: ELECTRON POSITRON
JET: ELECTROPRODUCTION
ELECTROPRODUCTION: JET
JET: MULTIPLE PRODUCTION
MULTIPLE PRODUCTION: JET
FINAL STATE: (3JET)
(3JET): FINAL STATE

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Analysis of Multi - Jet Final States in e+e−e^+ e^-e+e− Annihilation

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Analysis of Multi - Jet Final States in $e^+ e^-$ Annihilation