Non-global jet evolution at finite Nc Original Research Article

Resummations of soft gluon emissions play an important role in many applications of QCD, among them jet observables and small x saturation effects. For the case of non-global observables, Banfi, Marchesini, and Smye have cast the problem in terms of an evolution equation that exhibits a remarkable analogy with the BK equation used in the small x context. Here, this analogy is used to generalize the former beyond the leading Nc approximation. The result shows striking analogy with the JIMWLK equation describing the small x evolution of the color glass condensate. A Langevin description allows numerical implementation and provides clues for the formulation of closed forms for amplitudes at finite Nc. The proof of the new equation is based on amplitudes with ordered soft emission. It is fully independent of the derivation of the JIMWLK equation and thus sheds new light also on this topic.