Automating scattering amplitudes with chirality flow

Andrew Lifson, Malin Sjödahl, Zenny Wettersten

Research output: Contribution to journalArticlepeer-review


Recently we introduced the chirality-flow formalism, a method which builds on the spinor-helicity formalism and is inspired by the color-flow idea in QCD. With this formalism, Feynman rules and diagrams are simplified to the extent that it is often possible to immediately, by hand, write down a helicity amplitude given a Feynman diagram. In this paper we show that the method can also speed up numerical evaluation of scattering amplitudes by considering e+e- going to n photons in a MadGraph-based tree-level implementation. We find that the computation time is reduced by roughly a factor ten for six photons, and that it scales better with the number of external particles than the default MadGraph5_aMC@NLO implementation. This performance gain is in part attributed to the more compact Lorentz structures involved, and in part due to a transparent choice of gauge reference vectors which reduces the number of Feynman diagrams considered.

Original languageEnglish
Article number535
JournalEuropean Physical Journal C
Issue number6
Publication statusPublished - 2022 Jun

Subject classification (UKÄ)

  • Other Physics Topics


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