G. Abbiendi et al., Search for trilinear neutral gauge boson couplings in Z gamma production at root s=189 GeV at LEP, EUR PHY J C, 17(4), 2000, pp. 553-566
The data recorded at a centre-of-mass energy of 189 GeV by the OPAL detecto
r at LEP are used to search for trilinear couplings of the neutral gauge bo
sons in the process e(+)e(-) --> Z gamma. The cross-sections for multihadro
nic events with an energetic isolated photon, and for events with a high en
ergy photon accompanied by missing energy are measured. These cross-section
s and the photon energy, polar angle and isolation angle distributions are
compared to the Standard Model predictions and to the theoretical expectati
ons of a model allowing for Z gammaZ and Z gamma gamma vertices. Since no s
ignificant deviations with respect to the Standard Model expectations are f
ound, constraints are derived on the strength of neutral trilinear gauge co
uplings.