Principal value resummation

We present a new resummation formula for the Drell-Yan cross section. The formal resummation of threshold corrections in Drell-Yan hard-scattering functions produces an exponent with singularities from the infrared pole of the QCD running coupling. Our reformulation treats such "infrared renormalons" by a principal value prescription, analogous to a modified Borel transform. The resulting expression includes all large threshold corrections to the hard-scattering function as an asymptotic series in α_s, but is a finite function of Q². We find that the ambiguities of the resummed perturbation theory imply the presence of higher twist corrections to quark-antiquark hard-scattering functions that begin at v{inverted}_QCD/Q. This suggests an important role for higher twist in the phenomenology of hadron-hadron inclusive cross sections. We also discuss the numerical evaluation of the exponent and its asymptotic perturbation series for representative values of Q².