Production of single W Bosons at √s = GeV and measurement of WWγ gauge couplings

Single W boson production in electron-positron collisions is studied with the L3 detector at LEP. The data sample collected at a centre-of-mass energy of √s = 188.7 corresponds to an integrated luminosity of 176.4 pb −1 . Events with a single energetic lepton or two acoplanar hadronic jets are selected. Within phase-space cuts, the total cross-section is measured to be 0.53±0.12±0.03 pb, consistent with the standard model expectation. Including our single W boson results obtained at lower √s, the WWγ gauge couplings κ γ and λ γ are determined to be κ γ =0.93±0.16±0.09 and λ γ =−0.31 +0.68 −0.19 ±0.13.