Soft gluon evolution and non-global logarithms

Rene Angeles Martinez, Matthew De Angelis, Jeffrey R. Forshaw, Simon Plätzer, Michael H. Seymour

We consider soft-gluon evolution at the amplitude level. Our evolution algorithm applies to generic hard-scattering processes involving any number of coloured partons and we present a reformulation of the algorithm in such a way as to make the cancellation of infrared divergences explicit. We also emphasise the special role played by a Lorentz-invariant evolution variable, which coincides with the transverse momentum of the latest emission in a suitably defined dipole zero-momentum frame. Handling large colour matrices presents the most significant challenge to numerical implementations and we present a means to expand systematically about the leading colour approximation. Specifically, we present a systematic procedure to calculate the resulting colour traces, which is based on the colour flow basis. Identifying the leading contribution leads us to re-derive the Banfi-Marchesini-Smye equation. However, our formalism is more general and can systematically perform resummation of contributions enhanced by the t'Hooft coupling alpha N-s similar to 1, along with successive perturbations that are parametrically suppressed by powers of 1/N. We also discuss how our approach relates to earlier work.

Particle Physics
External organisation(s)
Polish Academy of Sciences (PAS), University of Manchester, European Organization for Nuclear Research (CERN)
Journal of High Energy Physics
No. of pages
Publication date
Peer reviewed
Austrian Fields of Science 2012
103012 High energy physics
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