title: Two-loop anomalous-dimension matrix for soft-gluon exchange.
abstract: The resummation of soft-gluon exchange for QCD hard scattering requires a matrix of anomalous dimensions. We compute this matrix directly for arbitrary 2-->n massless processes for the first time at two loops. Using color-generator notation, we show that it is proportional to the one-loop matrix. This result reproduces all pole terms in dimensional regularization of the explicit calculations of massless 2-->2 amplitudes in the literature, and it predicts all poles at next-to-next-to-leading order in any 2-->n process that has been computed at next-to-leading order. The proportionality of the one- and two-loop matrices makes possible the resummation in closed form of the next-to-next-to-leading logarithms and poles in dimensional regularization for the 2-->n processes.
authors.affiliation: C.N. Yang Institute for Theoretical Physics, Stony Brook University, Stony Brook, New York 11794-3840, USA.
authors.forename: S Mert
authors.initials: SM
authors.lastname: Aybat
authors.forename: Lance J
authors.initials: LJ
authors.lastname: Dixon
authors.forename: George
authors.initials: G
authors.lastname: Sterman