Operator analysis of pT-widths of TMDs

D. Boer*, M. G. A. Buffing, P. J. Mulders

*Corresponding author for this work

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Abstract

Transverse momentum dependent (TMD) parton distribution functions (PDFs), TMDs for short, are defined as the Fourier transform of matrix elements of non-local combinations of quark and gluon fields. The nonlocality is bridged by gauge links, which for TMDs have characteristic paths (future or past pointing), giving rise to a process dependence that breaks universality. It is possible, however, to construct sets of universal TMDs of which in a given process particular combinations are needed with calculable, process-dependent, coefficients. This occurs for both T-odd and T-even TMDs, including also the unpolarized quark and gluon TMDs. This extends the by now well-known example of T-odd TMDs that appear with opposite sign in single-spin azimuthal asymmetries in semi-inclusive deep inelastic scattering or in the Drell-Yan process. In this paper we analyze the cases where TMDs enter multiplied by products of two transverse momenta, which includes besides the p(T)-broadening observable, also instances with rank-2 structures. To experimentally demonstrate the process dependence of the latter cases requires measurements of second harmonic azimuthal asymmetries, while the p(T)-broadening will require measurements of processes beyond semi-inclusive deep inelastic scattering or the Drell-Yan process. Furthermore, we propose specific quantities that will allow for theoretical studies of the process dependence of TMDs using lattice QCD calculations.

Original languageEnglish
Article number053
Number of pages16
JournalJournal of High Energy Physics
Issue number8
DOIs
Publication statusPublished - 13-Aug-2015

Keywords

  • QCD Phenomenology
  • TRANSVERSE-SPIN ASYMMETRIES
  • PARTON DISTRIBUTION-FUNCTIONS
  • STATE INTERACTIONS
  • HARD PROCESSES
  • SINGLE-SPIN
  • DRELL-YAN
  • TWIST-4
  • QCD
  • LEPTOPRODUCTION
  • DISTRIBUTIONS

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