TMD-factorization, Factorization Breaking and Evolution

TL;DR

This paper reviews the current state of TMD-factorization in perturbative QCD, highlighting where it holds or breaks, recent progress in calculations and evolution, and future directions for phenomenology.

Contribution

It provides a comprehensive overview of TMD-factorization, including recent advances, challenges, and strategies for future implementation in phenomenological studies.

Findings

Identification of cases where TMD-factorization is valid or likely to fail.

Recent progress in TMD evolution calculations.

Discussion of future strategies for phenomenological applications.

Abstract

We give an overview of the current status of perturbative QCD factorization theorems in processes that involve transverse momentum dependent (TMD) parton distribution functions (PDFs) and fragmentation functions (FF). We enumerate those cases where TMD-factorization is well-established, and mention cases where it is likely to fail. We discuss recent progress in the implementation of specific TMD-factorization calculations, including the implementation of evolution. We also give examples of hard part calculations. We end by discussing future strategies for the implementation of TMD-factorization in phenomenological applications.