Study of the e^+e^- --> Z gamma Process at LEP and Limits on Triple Neutral-Gauge-Boson Couplings

TL;DR

This study measures the e^+e^- --> Z gamma process at LEP energies, confirming Standard Model predictions and setting limits on possible new physics through triple neutral-gauge-boson couplings.

Contribution

First precise measurement of the e^+e^- --> Z gamma process at LEP energies and the most stringent limits on anomalous neutral-gauge-boson couplings to date.

Findings

Measured cross sections agree with Standard Model

Set limits on anomalous couplings from 0.3 to 2.3 TeV

Constrained new physics energy scales

Abstract

The process e^+e^- --> Z gamma, where the Z boson decays into hadrons or neutrinos, is studied with data collected with the L3 detector at LEP at centre-of-mass energies from 189 GeV up to 209 GeV. The cross sections are measured and found to be in agreement with the Standard Model predictions. Limits on triple neutral-gauge-boson couplings, forbidden in the Standard Model at tree level, are derived. Limits on the energy scales at which the anomalous couplings could be manifest are set. They range from 0.3 TeV to 2.3 TeV depending on the new physics effect under consideration.