Next-to-next-to-leading logarithmic threshold resummation for deep-inelastic scattering and the Drell-Yan process

The soft-gluon resummation exponents GN in moment space are investigated for the quark coefficient functions in deep-inelastic structure functions and the quark-antiquark contribution to the Drell-Yan cross section d sigma /dM. Employing results from two- and three-loop calculations we obtain the next-to-next-to-leading logarithmic terms alpha (s) (alpha (s) ln N)(n) of G(N) to all orders in the strong coupling constant alpha (s). These new contributions facilitate a reliable assessment of the numerical effect and the stability of the large-N expansion. (C) 2001 Elsevier Science B.V. All rights reserved.