Factorization of large-x quark distributions in a hadron

We present a factorization formula for valence quark distributions in a hadron in x -> 1 limit. For the example of pion, we arrive at the form of factorization by analyzing momentum flow in the leading and high-order Feynman diagrams. The result confirms the well-known 1 - x scaling rule to all orders in perturbation theory, providing the nonperturbative matrix elements for the infrared divergence factors. We comment on resummation of perturbative single and double logarithms in 1 - x. (c) 2005 Elsevier B.V. All rights reserved.