$W\gamma \gamma$ Production at the Fermilab Tevatron Collider: Gauge Invariance and Radiation Amplitude Zero

Abstract

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

Comments: 37 pages,12 figures, postscript file also available via anonymous ftp at ftp://ucdhep.ucdavis.edu/han/vvv/Wgmgm.ps