Measurement of the W+W-gamma Cross Section and Direct Limits on Anomalous Quartic Gauge Boson Couplings at LEP

TL;DR

This study measures the W+W-gamma production cross section at LEP and sets limits on possible anomalous quartic gauge couplings, confirming consistency with the Standard Model within experimental uncertainties.

Contribution

The paper provides the first measurement of the W+W-gamma cross section at LEP energies and establishes new limits on anomalous quartic gauge boson couplings.

Findings

Measured W+W-gamma cross section: 290 +/- 80 +/- 16 fb.

Set 95% CL limits on anomalous couplings: -0.043 to 0.043 GeV^-2 for a_0/Lambda^2.

Results are consistent with Standard Model predictions.

Abstract

The process e+e- -> W+W-gamma is analysed using the data collected with the L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W- candidates containing an isolated hard photon, the W+W-gamma cross section, defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80 +/- 16 fb, consistent with the Standard Model expectation. Including the process e+e- -> nu nu gamma gamma, limits are derived on anomalous contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 < a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2.