Automating dipole subtraction
K. Hasegawa, S. Moch, P. Uwer
TL;DR
Automates Catani-Seymour dipole subtraction to handle IR divergences in NLO QCD real emissions. The framework uses a Mathematica-based dipole generator to produce all subtraction terms and an interface to MadGraph to evaluate color-linked Born squared matrix elements and helicity-dependent CLBS, exporting optimized C/Fortran code. It is tested on high-multiplicity processes (e.g., gg → u ubar g, gg → u ubar ggg) and demonstrates generation of up to about 100 dipoles. The approach enables fully automatic, process-independent IR-safe calculations and plans for public release.
Abstract
We report on automating the Catani-Seymour dipole subtraction which is a general procedure to treat infrared divergences in real emission processes at next-to-leading order in QCD. The automatization rests on three essential steps: the creation of the dipole terms, the calculation of the color linked squared Born matrix elements, and the evaluation of different helicity amplitudes. The routines have been tested for a number of complex processes, such as the real emission process gg --> t anti-t ggg.