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.

This month's issue has the following articles: (1) The Power of Partnership--Livermore researchers forge strategic collaborations with colleagues from other University of California campuses to further science and better protect the nation; (2) Collaborative Research Prepares Our Next-Generation Scientists and Engineers--Commentary by Laura R. Gilliom; (3) Next-Generation Scientists and Engineers Tap Lab's Resources--University of California Ph.D. candidates work with Livermore scientists and engineers to conduct fundamental research as part of their theses; (4) The Best and the Brightest Come to Livermore--The Lawrence Fellowship Program attracts the most sought-after postdoctoral researchers to the Laboratory; and (5) Faculty on Sabbatical Find a Good Home at Livermore--Faculty members from around the world come to the Laboratory as sabbatical scholars.

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