PDF factorization in hadron-hadron collisions
Davison Soper (Oregon U.)

The cross section for an infrared safe observable in hadron-hadron collisions can be written as the convolution of parton distribution functions (PDFs) for the two hadrons and a perturbatively calculable hard scattering function, with power suppressed corrections. The arguments that this PDF factorization works at all orders of perturbation theory involves the cancellation of what are called Glauber singularities from soft gluons that interact with both hadrons. I illustrate the arguments used in a 1988 paper with Collins and Sterman by applying these arguments to graphs at the lowest order in which the Glauber problems appear. We can see in this simple example how the contributions from Glauber singularities disappear. This sort of analysis is perhaps useful for the analysis of "non-global" logarithms in certain observables.