Automation of next-to-leading order computations in QCD: the FKS subtraction

TL;DR

This paper introduces a fully automated method for next-to-leading order QCD calculations using the FKS subtraction formalism, compatible with MadGraph, and effective for complex processes including BSM theories.

Contribution

It provides the first complete automation of the FKS subtraction method for NLO QCD computations, integrated with MadGraph and applicable to a wide range of theories.

Findings

Implementation is efficient for high-multiplicity final states.

Number of subtraction terms grows very mildly with multiplicity.

Demonstrated successful computation of sample processes.

Abstract

We present the complete automation of the universal subtraction formalism proposed by Frixione, Kunszt, and Signer for the computation of any cross section at the next-to-leading order in QCD. Given a process, the only ingredient to be provided externally is the infrared- and ultraviolet-finite contribution of virtual origin. Our implementation, currently restricted to the case of e+e- collisions, is built upon and works in the same way as MadGraph. It is particularly suited to parallel computation, and it can deal with any physical process resulting from a theory implemented in MadGraph, thus including the Standard Model as well as Beyond the Standard Model theories. We give results for some sample processes that document the performances of the implementation, and show in particular how the number of subtraction terms has an extremely mild growth with final-state multiplicity.