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 non-perturbative matrix elements for the infrared-divergence factors. We comment on re-summation of perturbative single and double logarithms in 1-x. 
Xiangdong Ji, Jian-Ping Ma, and Feng Yuan