CSS Equation, etc, Follow from Structure of TMD Factorization

Abstract

I show that the forms of the Collins-Soper-Sterman and renormalization-group equations for the evolution of transverse-momentum-dependent (TMD) parton densities in QCD follow from the structure of TMD factorization. A derivation does not need to directly use detailed properties of the operator definition of the TMD parton densities.

Comments: 9 pages. Sign of right-hand-side of Eq. (7) corrected