Two-loop QED and QCD corrections to massless fermion-boson scattering

We present the NNLO QCD virtual corrections for q (q) over bar --> ggamma, q (1) over bar --> gammagamma and the NNLO QED virtual corrections for e(-)e(+) --> gammagamma, and all processes related by crossing symmetry. We perform an explicit evaluation of the two-loop diagrams in conventional dimensional regularisation, and our results are renormalised in the MS scheme. The infrared pole structure of the amplitudes is in agreement with the prediction of Catani's general formalism for the singularities of two-loop amplitudes, while expressions for the finite remainder are given for all processes in terms of logarithms and polylogarithms that are real in the physical region. (C) 2002 Elsevier Science B.V. All rights reserved.