Search for Trilinear Neutral Gauge Boson Couplings in Z-gamma production at sqrt(s)=189GeV at LEP

TL;DR

This study analyzes LEP data at 189GeV to search for possible anomalous Z-gamma interactions, finding no deviations from the Standard Model and setting limits on neutral gauge couplings.

Contribution

First search for trilinear neutral gauge boson couplings in Z-gamma production at LEP energies, providing constraints on new physics beyond the Standard Model.

Findings

No significant deviations from Standard Model predictions.

Constraints placed on the strength of Z-gamma-Z and Z-gamma-gamma couplings.

Cross-section measurements consistent with theoretical expectations.

Abstract

The data recorded at a centre-of-mass energy of 189GeV by the OPAL detector at LEP are used to search for trilinear couplings of the neutral gauge bosons in the process e+e- --> Z-gamma. The cross-sections are measured for multihadronic events with an energetic isolated photon and for events with a high energy photon accompanied by missing energy. These cross-sections and the photon energy, polar angle and isolation angle distributions are compared to the Standard Model predictions and to the theoretical expectations of a model allowing for Z-gamma-Z and Z-gamma-gamma vertices. Since no significant deviations with respect to the Standard Model expectations are found, constraints are derived on the strength of neutral trilinear gauge couplings.