Soft gluon evolution and non-global logarithms

René Ángeles Martínez, Matthew De Angelis, Jeffrey R. Forshaw, Simon Plätzer, Michael H. Seymour

    Research output: Contribution to journalArticlepeer-review


    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 αsN ∼ 1, along with successive perturbations that are parametrically suppressed by powers of 1/N. We also discuss how our approach relates to earlier work.

    Original languageEnglish
    Article number44
    JournalJournal of High Energy Physics
    Issue number5
    Publication statusPublished - 8 May 2018


    • 1/N Expansion
    • Perturbative QCD
    • Resummation
    • Scattering Amplitudes


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