Masses, fermions and generalized D-dimensional unitarity

TL;DR

This paper extends the D-dimensional unitarity method to include massive particles, enabling the numerical calculation of one-loop amplitudes involving massive fermions in QCD, with validation through explicit amplitude computations.

Contribution

The authors develop a generalized D-dimensional unitarity approach that incorporates massive particles, addressing algebraic and renormalization issues for more accurate amplitude calculations.

Findings

Successfully computed one-loop amplitudes with massive quarks and gluons.

Validated the method with QCD scattering amplitude calculations.

Enhanced the applicability of unitarity methods to massive particle processes.

Abstract

We extend the generalized D-dimensional unitarity method for numerical evaluation of one-loop amplitudes by incorporating massive particles. The issues related to extending the spinor algebra to higher dimensions, treatment of external self-energy diagrams and mass renormalization are discussed within the context of the D-dimensional unitarity method. To validate our approach, we calculate in QCD the one-loop scattering amplitudes of a massive quark pair with up to three additional gluons for arbitrary spin states of the external quarks and gluons.