Improvements on dipole shower colour

Jack Holguin, Jeffrey R. Forshaw, Simom Plätzer

Research output: Contribution to journalArticlepeer-review


The dipole formalism provides a powerful framework from which parton showers can be constructed. In a recent paper (Forshaw et al. 2020), we proposed a dipole shower with improved colour accuracy and in this paper we show how it can be further improved. After an explicit check at O(αs2) we confirm that our original shower performs as it was designed to, i.e. inheriting its handling of angular-ordered radiation from a coherent branching algorithm. We also show how other dipole shower algorithms fail to achieve this. Nevertheless, there is an O(αs2) topology where it differs at sub-leading N c from a coherent branching algorithm. This erroneous topology can contribute a leading logarithm to some observables and corresponds to emissions that are ordered in k t but not angle. We propose a simple, computationally efficient way to correct this and assign colour factors in accordance with the coherence properties of QCD to all orders in α s.

Original languageEnglish
Article number364
JournalThe European Physical Journal C
Issue number4
Publication statusPublished - 27 Apr 2021


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