Higher-order corrections in threshold resummation

We extend the threshold resummation exponents G(N) in Mellin-N space to the fourth logarithmic ((NLL)-L-3) order collecting the terms alpha(2)(s) (as ln N)(n) to all orders in the strong coupling constant as. Comparing the results to our previous three-loop calculations for deep-inelastic scattering (DIS), we derive the universal coefficients B-q and B-g governing the final-state jet functions to order alpha(3)(S) extending the previous quark and gluon results by one and two orders. A curious relation is found at second order between these quantities, the splitting functions and the large-angle soft emissions in Drell-Yan type processes. We study the numerical effect of the (NLL)-L-3 corrections using both the fully exponentiated form and the expansion of the coefficient function in towers of logarithms. (c) 2005 Elsevier B.V. All rights reserved.