G. Abbiendi et al., Measurement of the W+W- gamma cross-section and first direct limits on anomalous electroweak quartic gauge couplings, PHYS LETT B, 471(2-3), 1999, pp. 293-307
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 183 pb(-1) of data recorde
d at root s = 189 GeV. From these data, 17 W+W- gamma candidates are select
ed with photon energy greater than 10 GeV, consistent with the Standard Mod
el expectation. These events are used to measure the e(+)e(-) --> W+W- gamm
a cross-section within a set of geometric and kinematic cuts, <(sigma)over
cap>(WW gamma) = 136 +/- 37 +/- 8 fb, where the first error is statistical
and the second systematic. The photon energy spectrum is used to set the fi
rst direct, albeit weak, limits on possible anomalous contributions to the
W+W- gamma gamma and W+W- gamma Z(0) vertices:
0.070GeV(-2) < a(0)/Lambda(2) < 0.070 GeV-2,
0.13GeV(-2) < a(c)/Lambda(2) < 0.19 GeV-2,
0.61GeV(-2) < a(n)/Lambda(2) < 0.57 GeV-2,
where Lambda represents the energy scale for new physics. (C) 1999 Publishe
d by Elsevier Science B.V. All rights reserved.