Improvements on dipole shower colour

Jack Holguin; Jeffrey R. Forshaw; Simon Plätzer

doi:10.1140/epjc/s10052-021-09145-1

paper

Improvements on dipole shower colour

arXiv:2011.15087 · doi:10.1140/epjc/s10052-021-09145-1

Abstract

The dipole formalism provides a powerful framework from which parton showers can be constructed. In a recent paper, 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 $O (α_{s}^{2})$ 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 $O (α_{s}^{2})$ 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 $α_{s}$ .

arXiv comment26 pages, 2 appendices, 9 figures. Version 2 contains small changes and is inline with the version published in EPJ C

Improvements on dipole shower colour

Abstract

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