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arXiv · 2312.07447

Simplifying QCD event generation with chirality flow, reference vectors and spin directions

Emil Boman·Andrew Lifson·Malin Sjodahl·Adam Warnerbring·Zenny Wettersten
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Abstract

The chirality-flow formalism, combined with good choices of gauge reference vectors, simplifies tree-level calculations to the extent that it is often possible to write down amplitudes corresponding to Feynman diagrams immediately. It has also proven to give a very sizable speedup in a proof of concept implementation of massless tree-level QED in MadGraph5_aMC@NLO. In the present paper we extend this analysis to QCD, including massive quarks. We define helicity-dependent versions of the gluon vertices, derive constraints on the spinor structure of propagating gluons, and explore the Schouten identity to simplify the four-gluon vertex further. For massive quarks, the chirality-flow formalism sheds light on how to exploit the freedom to measure spin along any direction to shorten the calculations. Overall, this results in a clear speedup for treating the Lorentz structure at high multiplicities.

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Emil Boman, Andrew Lifson, Malin Sjodahl, Adam Warnerbring, Zenny Wettersten. 2023-12-12. Simplifying QCD event generation with chirality flow, reference vectors and spin directions. https://arxiv.org/abs/2312.07447

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