  We analyze transverse momentum ($Q_T$) resummation of a colorless final
state, e.g. Higgs production in gluon fusion or the production of a lepton pair
via the Drell-Yan mechanism, in the limit where the invariant mass of the final
state is much less then the center-of-mass energy, i.e. $Q^2\ll s$. We show how
the traditional resummation of logarithms of $Q_T/Q$ can be supplemented with
the resummation of the leading logarithmic contributions at small $x=Q^2/s$ and
we compute the necessary ingredients to perform such joint resummation.

High Energy Physics - Phenomenology