CSW rules for a massive scalar

TL;DR

This paper extends the CSW diagrammatic rules to include massive scalars in four-dimensional Yang-Mills theory, introducing new vertices and simplifying amplitude calculations involving mass.

Contribution

It derives novel CSW rules for massive scalars directly from an action, expanding the applicability of these rules beyond massless cases.

Findings

New vertices for massive scalars are introduced.

Rules are validated against known results.

Simplifies proofs of on-shell recursion relations.

Abstract

We derive the analog of the Cachazo-Svrcek-Witten (CSW) diagrammatic Feynman rules for four dimensional Yang-Mills gauge theory coupled to a massive colored scalar. The mass term is shown to give rise to a new tower of vertices in addition to the CSW vertices for massless scalars in non-supersymmetric theories. The rules are derived directly from an action, once through a canonical transformation within light-cone Yang-Mills and once by the construction of a twistor action. The rules are tested against known results in several examples and are used to simplify the proof of on-shell recursion relations for amplitudes with massive scalars.