One-loop leading logarithms in electroweak radiative corrections - II. Factorization of collinear singularities

We discuss the evaluation of the collinear single-logarithmic contributions to virtual electroweak corrections at high energies. More precisely, we pr ove the factorization of the mass singularities originating from loop diagr ams involving collinear virtual gauge bosons coupled to external legs. We d iscuss, in particular, processes involving external longitudinal gauge boso ns, which are treated using the Goldstone-boson equivalence theorem. The pr oof of factorization is performed within the 't Hooft-Feynman gauge at one- loop order and applies to arbitrary electroweak processes that are not mass -suppressed at high energies. As basic ingredients we use Ward identities f or Green functions with arbitrary external particles involving a gauge boso n collinear to one of these. The Ward identities are derived from the BRS i nvariance of the spontaneously broken electroweak gauge theory.