Exploration of the Tree-Level S-Matrix of Massless Particles

TL;DR

This paper investigates the boundary terms in the BCFW recursion relations for massless particles, proposing new on-shell recursion methods to better understand the perturbative structure of the S-matrix.

Contribution

It introduces a novel set of on-shell recursion relations applicable when amplitudes do not vanish at infinity, advancing the understanding of scattering amplitudes.

Findings

New recursion relations for non-vanishing boundary terms

Insights into the perturbation theory structure of the S-matrix

Enhanced computational techniques for scattering amplitudes

Abstract

In recent years, the BCFW construction provided a very powerful tool for computing scattering amplitudes as well as it shed light on the perturbation theory structure. In this talk, we discuss the long-standing issue of the boundary term arising when the amplitudes do not vanish as some momenta are taken to infinity along some complex direction. In particular, we provide a new set of on-shell recursion relations valid for such theories and discuss its consequences on our understanding on the perturbation theory structure of the S-Matrix.