Measurement of the W+W−γ cross-section and first direct limits on anomalous electroweak quartic gauge couplings

Abbiendi, G and Ackerstaff, K and Akesson, P F and Alexander, G and Allison, J and Anderson, K J and Arcelli, S and Asai, S and Ashby, S F and Axen, D and Azuelos, G and Bailey, I and Ball, A H and Barberio, E and Barlow, R J and Batley, J R and Baumann, S and Behnke, T and Bell, K W and Bella, G and Bellerive, A and Bentvelsen, S and Bethke, S and Betts, S and Biebel, O and Biguzzi, A and Bloodworth, I J and Bock, P and Bohme, J and Boeriu, O and Bonacorsi, D and Boutemeur, M and Braibant, S and Bright-Thomas, P and Brigliadori, L and Brown, R M and Burckhart, H J and Capiluppi, P and Carnegie, R K and Carter, A A and Carter, J R and Chang, C Y and Charlton, D G and Chrisman, D and Ciocca, C and Clarke, P E L and Clay, E and Cohen, I and Conboy, J E and Kartvelishvili, V (1999) Measurement of the W+W−γ cross-section and first direct limits on anomalous electroweak quartic gauge couplings. Physics Letters B, 471 (2-3). pp. 293-307. ISSN 0370-2693

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 183 pb(-1) of data recorded at root s = 189 GeV. From these data, 17 W+W- gamma candidates are selected with photon energy greater than 10 GeV, consistent with the Standard Model expectation. These events are used to measure the e(+)e(-) --> W+W- gamma 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 first 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 Published by Elsevier Science B.V. All rights reserved.