Coordinate-space picture and $x\to 1$ singularities at fixed $k_{\perp }$

Abstract

We discuss ongoing progress towards precise characterizations of parton distributions at fixed transverse momentum, focusing on matrix elements in coordinate space and the treatment of endpoint singularities.

Comments: Based on talks given at the "HERA and the LHC" Workshop (Hamburg, March 2007) and at the "DIS07" Workshop (Munich, April 2007)