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Perturbative corrections to quark TMDPDFs in the background-field method: Gauge invariance, equations of motion, and multiple interactions

Swagato Mukherjee1, Vladimir V. Skokov2, Andrey Tarasov2,3,*, and Shaswat Tiwari2,†

  • *Contact author: ataraso@ncsu.edu
  • †Contact author: sstiwari@ncsu.edu
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Phys. Rev. D 111, 114034 – Published 26 June, 2025

DOI: https://doi.org/10.1103/zrz3-3rbh

Abstract

We calculate the perturbative corrections in the strong coupling to the unpolarized quark transverse-momentum dependent parton distribution function (TMDPDF) operator within a background-field framework, extending the approach of Mukherjee et al. [Phys. Rev. D 109, 034035 (2024)]. We focus on ensuring gauge invariance, identifying two key components needed: a gauge-invariant TMDPDF operator with a transverse gauge link at spatial infinity, and accounting of the equations of motion (EoM) of the background fields. We go beyond next-to-leading order in strong coupling expansion, considering multiple interactions with the background field at all orders of strong coupling. By examining the interplay between quark and gluon contributions, we show that spurious singularities, proportional to EoM, can be misinterpreted as genuine divergences in quantum chromodynamics factorization unless properly identified and removed.

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Unified description of DGLAP, CSS, and BFKL evolution: TMD factorization bridging large and small x

Swagato Mukherjee, Vladimir V. Skokov, Andrey Tarasov, and Shaswat Tiwari
Phys. Rev. D 109, 034035 (2024)

Article Text

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Phys. Rev. D 111, 114034– Published 26 June, 2025
  • Received 27 March 2025
  • Accepted 3 June 2025
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