Evidence for the Absence of Gluon Orbital Angular Momentum in the Nucleon

Abstract

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.

13 pages, clarifications and refs. added, version to appear in PLB

References in corpus (3)

• What exactly is a parton density?
• Constraints on the gluon Sivers distribution via transverse single spin asymmetries at midrapidity in p(transv. polarized) p -> pi^0 X processes at BNL RHIC
• Discrete Symmetries on the Light Front and a General Relation Connecting Nucleon Electric Dipole and Anomalous Magnetic Moments

Cited by in corpus (13)

• Relations between generalized and transverse momentum dependent parton distributions
• Sivers Effect for Pion and Kaon Production in Semi-Inclusive Deep Inelastic Scattering
• Azimuthal and Single Spin Asymmetries in Hard Scattering Processes
• Heavy Quarkonium Production in Single Transverse Polarized High Energy Scattering
• Transverse Spin Structure of the Nucleon through Target Single Spin Asymmetry in Semi-Inclusive Deep-Inelastic $(e,e^{\prime }{\pi }^{\pm })$ Reaction at Jefferson Lab
• A quark model analysis of the Sivers function
• Connection between the Sivers function and the anomalous magnetic moment
• Model calculations of the Sivers function satisfying the Burkardt Sum Rule
• Measurement of Transverse Single-Spin Asymmetries for J/psi Production in Polarized p+p Collisions at sqrt(s) = 200 GeV
• Neutron single spin asymmetries from semi-inclusive deep inelastic scattering off transversely polarized ${}^3$He
• Phenomenological analysis of the nucleon spin contents and their scale dependence
• Orbital angular momentum of the proton and intrinsic five-quark Fock states
• The neutron transversity from semi-inclusive DIS off 3He