Abstract

In a recent paper we introduced the chirality-flow formalism, a method for simple and transparent calculations of Feynman diagrams based on the left- and right-chiral mathfrak {sl}(2,mathbb {C}) nature of spacetime. While our previous work focused on massless QED and QCD at tree-level, we here extend the chirality-flow formalism to the full (tree-level) Standard Model, including massive particles and electroweak interactions – for which the W-interaction simplifies elegantly due to its chiral nature. We illustrate how values of Feynman diagrams can be immediately written down with some representative examples.

Highlights

  • In a recent paper [1] we introduced the chirality-flow formalism – a flow-like method for treating the Lorentz structure of scattering amplitudes – together with its tree-level Feynman rules in massless QED and QCD

  • For physics beyond the Standard Model, we note that it is possible to use chirality-flow to describe any theory for which the Lorentz structure can be written down in terms of momenta, the (Minkowski) metric, Dirac (Pauli) matrices, massless Weyl spinors, and polarization vectors

  • This vertex enters in the Standard Model only at loop level, but we include it here to complete the list of Standard Model Lorentz structures

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Summary

Introduction

In a recent paper [1] we introduced the chirality-flow formalism – a flow-like method for treating the Lorentz structure of scattering amplitudes – together with its tree-level Feynman rules in massless QED and QCD. This method builds on the spinor-helicity formalism [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17] and is inspired by the color-flow decomposition of the color structure of gluons into fundamental and anti-fundamental representations [18,19,20] It decomposes the Lorentz structure of spin-one bosons into the dotted and undotted left- and right-chiral fields of the Weyl-van-der-Waerden formalism [21,22,23,24,25,26,27,28,29], denoted by dotted and undotted lines respectively, and corresponding to the two sl(2, C) copies of spacetime.

Massless chirality-flow
Weyl spinors
Massless fourvectors
Polarization vectors
The chirality-flow formalism with massive particles
Linking objects
Massive fourvectors
Helicity and the eigenvalue decomposition
Dirac spinors from massless Weyl spinors
Helicity eigenstates
Triple vertices
Chirality-flow Feynman rules with massive particles
Four-boson vertices
Chirality-flow arrows and signs
Application
Examples
Conventions and the chiral representation
Relativistic spin operator for massive spinors
Explicit representations of spinors and their inner products
Full Text
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