Wγγ Production at the Fermilab Tevatron Collider : Gauge Invariance and Radiation Amplitude Zero

The electroweak process pp̄ → lνγγ is calculated at tree level, including finite W width effects. In order to obtain a gauge invariant amplitude, the imaginary parts of WWγ triangle graphs and WWγγ 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 pp̄ → Wγγ → lνγγ, and discuss how it may be observed in correlations of the γγ and lepton rapidities at the Fermilab Tevatron.