The standard theoretical tool of QCD, fixed-order perturbation theory, often leads to series expansions in the coupling that are insufficiently convergent to be of direct practical use. This is especially true when making predictions for hadronic final states. Over the past 20 years methods have been developed for analytically calculating dominant contributions at all orders of perturbation theory. These “resummation” techniques have been applied with success to comparisons with a number of experimentally well-measured observables.
The first part of this talk will introduce the ideas and structures that appear in resummed calculations, many of which are of remarkable simplicity. Despite this simplicity, actually carrying out resummations has in the past proved to be a delicate craft. Recently however, significant progress has been made towards developing a systematic framework for final-state resummations, as will be described in the second part of this talk.

LPTHE Jussieu/CNRS