One-loop QCD corrections to massless quark scattering at NNLO

We present the O(alpha (4)(s)) virtual QCD corrections to massless unlike-quark q (q) over bar --> q '(q) over bar ' and massless like-quark scattering q (q) over bar --> q (q) over bar due to the interference of one-loop amplitudes with one-loop amplitudes. The structure of the infrared divergences agrees with that predicted by Catani, The results are expressed in an analytic form so that the relevant expressions for crossed scattering processes can be obtained in a straightforward manner. The one-loop contributions presented here, together with the interference of tree with two-loop amplitudes given recently, complete the 2 --> 2 virtual QCD corrections at NNLO for the massless quark scattering processes, (C) 2001 Elsevier Science B.V. All rights reserved.