Transverse moments of TMD parton densities and ultraviolet divergences

Abstract

I review some open questions relating to the large transverse momentum divergences in transverse moments of transverse momentum dependent (TMD) parton correlation func- tions. I also explain, in an abbreviated and summarized form, recent work that shows that the resulting violations of a commonly used integral relation are not perturbatively suppressed. I argue that this implies a need for more precise definitions for the correlation functions used to describe transverse moments.

Comments: 11 pages, review, version published in Modern Physics Letters A, Originally prepared for DIS2020, canceled due to the Covid-19 epidemic