Integrand-reduction techniques for NLO and beyond

TL;DR

This paper reviews integrand-reduction techniques for NLO and higher-order calculations, highlighting the GoSam 2.0 framework's capabilities in automating one-loop computations and extending to NNLO and beyond.

Contribution

It introduces the GoSam 2.0 framework for automated one-loop calculations and discusses its extensions to NNLO and multivariate polynomial division methods for higher-loop reductions.

Findings

GoSam 2.0 effectively automates NLO calculations with Monte Carlo integration.

The framework has been extended to NNLO for real-virtual contributions.

A new approach for multivariate polynomial division for multi-loop integrand reduction.

Abstract

After a brief general introduction about the integrand-reduction method, we will review the main features of the GoSam 2.0 automated framework for one-loop calculations and illustrate its application to SM processes involving the production of massive particles in conjunction with jets and photons. These results have been obtained by interfacing GoSam with different Monte Carlo frameworks, thus combining the NLO calculation with parton shower effects. In the second part of the presentation, we will focus on the applications of GoSam beyond NLO. The code has already been used within NNLO calculations for the computation of real-virtual contributions and for the evaluation of the hard functions needed by approximate NNLO and resummation techniques. We will finally briefly discuss a promising approach for the reduction of scattering amplitudes beyond one loop based on integrand reduction via multivariate polynomial division.