We propose to use high energy, k(perpendicular-to)-dependent, factoriz
ation (HEF) in electroweak fusion processes in order to systematically
improve the effective W approximation (EWA) at collider energies. Sta
rting from the example of top production, we show that HEF provides co
rrectly all quasi constant terms in the production cross section, i.e.
not only the ones O(1/M(W)2) which are typical of the EWA and are due
to longitudinal polarizations of exchanged bosons, but also the ones
O(1/M(t)2) which are partly due to transverse polarizations. It turns
out that the latter contributions cannot be accounted for by collinear
factorization only, but also come from longitudinal off-shell effects
, typical of broken gauge theories, which are explicitly evaluated her
e.