A coordinate description of partonic processes
  We review a perturbative description of amplitudes in coordinate space, aiming at an intuitive perspective on the roles of "long" and "short" distances. We begin with coordinate-space leading regions for fixed-angle scattering amplitudes, and develop approximations and factorizations in analogy to similar procedures in momentum space. There are also applications to products of Wilson lines, including the familiar cusp amplitude. We briefly discuss cross sections from the coordinate viewpoint, and the mechanism by which infrared singularities cancel in inclusive cross sections. 
Ozan Erdogan and George Sterman
hep-ph hep-th