Simple formula for the infrared singular part of the integrand of one-loop QCD amplitudes

Abstract

We show that a well-known simple formula for the explicit infrared poles of one-loop QCD amplitudes has a corresponding simple counterpart in unintegrated form. The unintegrated formula approximates the integrand of one-loop QCD amplitudes in all soft and collinear singular regions. It thus defines a local counterterm for the infrared singularities and can be used as an ingredient for the numerical calculation of one-loop amplitudes.