FeynCalc 10.2 and FeynHelpers 2: Multiloop calculations streamlined

TL;DR

This paper introduces FeynCalc 10.2 and FeynHelpers 2, expanding multiloop capabilities by linking FeynCalc with external tools for diagram generation (QGRAF), IBP reduction (FIRE, KIRA), and numerical evaluation (FIESTA, pySecDec), while enabling parallelization to harness multicore CPUs. It also presents a robust strategy for handling zero Gram determinant problems via FCLoopFindTensorBasis and outlines a streamlined workflow for end-to-end calculations within Mathematica. The work highlights practical demonstrations, including a two-loop H → gg example, and discusses maintenance and usability challenges inherent to public multi-software frameworks. Together, these updates make complex multiloop computations more accessible, reproducible, and scalable for researchers, with future plans for broader integration (LoopScalla) and extended interfaces.

Abstract

We present new versions of the Mathematica package FeynCalc and the FeynHelpers add-on that represent an important contribution to the collection of public codes for semi-automatic evaluation of multiloop Feynman diagrams. FeynHelpers enables interfacing between FeynCalc and selected programs routinely used in multiloop calculations such as QGRAF, FIRE, KIRA, FIESTA or pySecDec. In addition to that FeynCalc now supports parallelizing the execution of selected routines on multicore CPUs and can handle tensor integrals with zero Gram determinants where the traditional tensor reduction breaks down.