Threshold resummation in momentum space from effective field theory

Methods from soft-collinear effective theory are used to perform the threshold resummation of Sudakov logarithms for the deep-inelastic structure function F-2(x,Q(2)) in the end-point region x -> 1 directly in momentum space. An explicit all-order formula is derived, which expresses the short-distance coefficient function C in the convolution F-2=C circle times phi(q) in terms of Wilson coefficients and anomalous dimensions defined in the effective theory. Contributions associated with the physical scales Q(2) and Q(2)(1-x) are separated from nonperturbative hadronic physics in a transparent way. A crucial ingredient to the momentum-space resummation is the exact solution to the integro-differential evolution equation for the jet function, which is derived. The methods developed in this Letter can be applied to many other hard QCD processes.