Gauge invariant formulation of strong WW scattering
  Models of strong $WW$ scattering in the $s$-wave can be represented in a gauge invariant fashion by defining an effective scalar propagator that represents the strong scattering dynamics. The $\sigma(qq \ra qqWW)$ signal may then be computed in U-gauge from the complete set of tree amplitudes, just as in the standard model, without using the effective $W$ approximation (EWA). The U-gauge ``transcription'' has a wider domain of validity than the EWA, and it provides complete distributions for the final state quanta, including experimentally important jet distributions that cannot be obtained from the EWA. Starting from the usual formulation in terms of unphysical Goldstone boson scattering amplitudes, the U-gauge transcription is verified by using BRS invariance to construct the complete set of gauge and Goldstone boson amplitudes in $R_{\xi}$ gauge. 
Michael S. Chanowitz