LARGE PERTURBATIVE CORRECTIONS TO THE DRELL-YAN PROCESS IN QCD

The total cross section dσ dQ2 for the production of a muon pair of invariant mass Q2 via the Drell-Yan mechanism and the Feynman xF differential cross section d2σ dQ2dxF are calculated in QCD retaining all terms up to order αs(Q2. The calculations are performed using dimensional regularisation of the intermediary infrared and collinear singularities, but we present our results in a form independent of such details. The corrections to both these cross sections coming from radiative corrections to the lowest-order qq annihilation diagram are found to be large at present values of Q2 and S when the cross section is expressed in terms of parton densities derived from leptonproduction, for all Drell-Yan processes of practical interest. Numerical calculations are presented which show, for any reasonable parametrisation of the parton densities, that the neglect of higher-order terms in αs(Q2) is not justifiable. The quark-gluon diagrams on the other hand give small corrections in this order and are only important for PP scattering. © 1979.