We investigate small$-x$ resummation effects in QCD coefficient functions for $Z_0g$ and $Wg$ fusion processes, and we compare them with the known ones of $gamma g$ type. We find a strong process dependence, that we argue to be due to the possible presence of collinear singularities for either small or large $k$ of the exchanged gluon. For top quark production, we find that the $ggra tbar{t}$ and $Z_0gra tbar{t}$ channels have larger resummation enhancements than the $Wgra tbar{t}$ one.
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