A sample of 4148 four-jet events observed in the ALEPH-detector at LEP in 1989 and 1990 is used to test the underlying gauge group of strong interactions. A fit to the ratios of the "colour factors" C(F), N(C) and T(F), which determine the differential cross sections, yields N(C)/C(F) = 2.24 +/- 0.32stat +/- 0.24syst and T(F)/C(F) = 0.58 +/- 0.17stat +/- 0.23syst. This is in agreement with the values expected from QCD: N(C)/C(F) = 2.25 and T(F)/C(F) = 0.375. The non-zero value of N(C)/C(F) constitutes direct evidence for the existence of the triple-gluon coupling and excludes any abelian gauge theory by more than five standard deviations.

EVIDENCE FOR THE TRIPLE-GLUON VERTEX FROM MEASUREMENTS OF THE QCD COLOR FACTORS IN Z-DECAY INTO 4 JETS

LUSIANI, Alberto;ROLANDI, LUIGI;LIGABUE, FRANCO;
1992

Abstract

A sample of 4148 four-jet events observed in the ALEPH-detector at LEP in 1989 and 1990 is used to test the underlying gauge group of strong interactions. A fit to the ratios of the "colour factors" C(F), N(C) and T(F), which determine the differential cross sections, yields N(C)/C(F) = 2.24 +/- 0.32stat +/- 0.24syst and T(F)/C(F) = 0.58 +/- 0.17stat +/- 0.23syst. This is in agreement with the values expected from QCD: N(C)/C(F) = 2.25 and T(F)/C(F) = 0.375. The non-zero value of N(C)/C(F) constitutes direct evidence for the existence of the triple-gluon coupling and excludes any abelian gauge theory by more than five standard deviations.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11384/3613
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