Transverse-momentum parton densities: gauge links, divergences and soft factor
I.O. Cherednikov, N.G. Stefanis
TL;DR
This paper reviews the theoretical framework of transverse-momentum dependent parton densities, focusing on gauge links, divergences, and the soft factor, highlighting the advantages of lightcone axial gauge for consistent definitions.
Contribution
It provides an analysis of the renormalization, gauge link structure, and soft factor role in TMDs, emphasizing the benefits of lightcone axial gauge over other gauges.
Findings
Lightcone axial gauge simplifies TMD renormalization.
Gauge link structure affects divergence behavior.
Soft factor is crucial for TMD factorization.
Abstract
We discuss the state-of-the-art of the theory of transverse-momentum dependent parton densities (TMD)s, paying special attention to their renormalization properties, the structure of the gauge links in the operator definition, and the role of the soft factor in the factorization formula within the TMD approach to the semi-inclusive processes. We argue that the use of the lightcone axial gauge offers certain advantages for a consistent definition of TMDs as compared to the off-the-light-cone gauges, or covariant gauges with off-the-lightcone gauge links.
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