Scattering of Gravitons and Spinning Massive States from Compact Numerators

TL;DR

This paper introduces a new diagrammatic method within the scattering equations framework for efficiently computing tree-level amplitudes involving spinning massive particles, extending to non-integer spins and aiding classical gravity calculations.

Contribution

It presents a novel diagrammatic tool using exponential numerators for covariant amplitude calculations with spinning massive states, enabling non-integer spin extensions.

Findings

Efficient computation of amplitudes with spinning massive particles.

Extension of recurrence relations to non-integer spins.

Facilitation of classical gravity observable generation from on-shell amplitudes.

Abstract

We provide a new efficient diagrammatic tool, in the context of the scattering equations, for computation of covariant $D$-dimensional tree-level $n$-point amplitudes with pairs of spinning massive particles using compact exponential numerators. We discuss how this framework allows non-integer spin extensions of recurrence relations for amplitudes developed for integer spin. Our results facilitate the on-going program for generating observables in classical general relativity from on-shell tree amplitudes through the Kawai-Lewellen-Tye relations and generalized unitarity.