The electroweak process $p\overline{p}{\mathcal{l}}^{\pm }\nu \gamma \gamma$ is calculated at the tree level, including finite $W$ width effects. In order to obtain a gauge-invariant amplitude, the imaginary parts of $\mathrm{WW}\gamma$ triangle graphs and $\mathrm{WW}\gamma \gamma$ box diagrams have to be included, in addition to resumming the imaginary contributions to the $W$ vacuum polarization. We demonstrate the existence of a radiation amplitude zero in $p\overline{p}\to W^{\pm }\gamma \gamma \to {\mathcal{l}}^{\pm }\nu \gamma \gamma$, and discuss how it may be observed in correlations of the $\gamma \gamma$ and lepton rapidities at the Fermilab Tevatron.

• Received 19 February 1997

DOI:https://doi.org/10.1103/PhysRevD.56.140