Equality of Two Definitions for Transverse Momentum Dependent Parton   Distribution Functions
  We compare recent, seemingly different, approaches to TMD-factorization (due to Echevarria, Idilbi, and Scimemi and to Collins), and show that they are the same, apart from an apparent difference in their definition of the \MSbar{} renormalization scheme. 
John C. Collins and Ted C. Rogers
hep-ph hep-ex