Unification of the kT and threshold resummations

We derive a resummation formula for a kT-dependent parton distribution function at threshold, where kT is a parton transverse momentum. The derivation requires infrared cutoffs for both longitudinal and transverse loop momenta as evaluating soft gluon emissions in the Collins–Soper resummation framework. This unified resummation exhibits suppression at large b, b being the conjugate variable of kT, which is similar to the kT resummation, and exhibits enhancement at small b, similar to the threshold resummation.