One-loop Amplitudes: String Methods, Infrared Regularization, and Automation

TL;DR

This paper employs string-inspired methods to compute one-loop graviton amplitudes, introduces infrared regularization via higher-point kinematics, and offers code for automation.

Contribution

It presents a novel approach combining string techniques with infrared regularization and provides tools for automating amplitude calculations.

Findings

Infrared divergences are regulated using higher-point kinematics.

The method yields infrared finite tensor structure integrals.

Code implementation facilitates automation of amplitude computations.

Abstract

We calculate field theory loop amplitudes by string methods, applied to half-maximal 4-point one-loop graviton amplitudes. Infrared divergences are regulated similarly to soft-collinear effective field theory (SCET): new mass scales are introduced, here by higher-point kinematics. We use an analytically continued single-valued polylogarithm as generating function. The Feynman integrals for the new tensor structures are infrared finite. We provide code as a step towards automation.