Evidence for the absence of gluon orbital angular momentum in the nucleon

Stanley J. Brodsky, Susan Gardner

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


The Sivers mechanism for the single-spin asymmetry in unpolarized lepton scattering from a transversely polarized nucleon is driven by the orbital angular momentum carried by its quark and gluon constituents, combined with QCD final-state interactions. Both quark and gluon mechanisms can generate such a single-spin asymmetry, though only the quark mechanism can explain the small single-spin asymmetry measured by the COMPASS Collaboration on the deuteron, suggesting the gluon mechanism is small relative to the quark mechanism. We detail empirical studies through which the gluon and quark orbital angular momentum contributions, quark-flavor by quark-flavor, can be elucidated.

Original languageEnglish
Pages (from-to)22-28
Number of pages7
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number1
StatePublished - Nov 30 2006

Bibliographical note

Funding Information:
Work supported in part by the US Department of Energy under contracts DE-AC02-76SF00515 and DE-FG02-96ER40989.

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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