Measurement of the W+W-gamma Cross-section and First direct Limits on Anomalous Electroweak Quartic Gauge Couplings

TL;DR

This paper measures the W+W-gamma production cross-section at LEP and sets the first direct limits on anomalous electroweak quartic gauge couplings, providing insights into potential new physics beyond the Standard Model.

Contribution

It presents the first direct limits on anomalous electroweak quartic gauge couplings using W+W-gamma events at LEP, along with a measurement of the W+W-gamma cross-section.

Findings

Measured W+W-gamma cross-section: 136+-37+-8 fb.

Set limits on anomalous couplings: a_0, a_c, a_n.

Observed photon spectrum consistent with Standard Model.

Abstract

A study of W+W- events accompanied by hard photon radiation produced in e+e- collisions at LEP is presented. Events consistent with two on-shell W-bosons and an isolated photon are selected from 183pb^-1 of data recorded at root{s}=189GeV. From these data, 17 W+W-gamma candidates are selected with photon energy greater than 10GeV, consistent with the Standard Model expectation. These events are used to measure the e+e- to W+W-gamma cross-section within a set of geometric and kinematic cuts; sigma{W+W-gamma} = 136+-37+-8 fb, where the first error is statistical and the second systematic. The photon energy spectrum is used to set the first direct, albeit weak, limits on possible anomalous contributions to the {W+ W- gamma gamma} and {W+ W- gamma Z0} vertices: -0.070GeV^{-2} < a_0/Lambda^2 < 0.070GeV^{-2}, -0.13GeV^{-2} < a_c/Lambda^2 < 0.19GeV^{-2}, -0.61GeV^{-2} < a_n/Lambda^2 < 0.57GeV^{-2}, where Lambda represents the energy scale for new physics.