Resummation in Heavy Quark and Jet Cross Sections

We discuss corrections from the elastic limit (partonic threshold) in hadronic hard-scattering cross sections. We show why these corrections can be large at all orders in perturbation theory, and describe their resummation to arbitrary logarithmic accuracy. In particular, we discuss the role of color exchange in the hard scattering. This enables us to generalize the resummation of the Drell-Yan cross section to QCD reactions. As an example, we give the explicit resummed hard-scattering cross section for heavy-quark production through light quark annihilation, which takes into account next-to-leading logarithms to all orders.