The Quark Orbital Angular Momentum in a Light-Cone Representation

Abstract

We perform an analysis of the quark angular momentum in a light-cone representation by taking into account the effect due to the Melosh-Wigner rotation and find that there is a relativistic correction factor connecting the quark orbital angular momentum with the quark model spin distribution: $L_q(x)=<M_L(x)>\Delta q_{QM}(x)$. The quark orbital angular momentum $L_q(x)$ and the quark helicity distribution $\Delta q(x)$ are connected to the quark model spin distribution $\Delta q_{QM}(x)$ by a relation: $\frac{1}{2}\Delta q(x)+L_q(x)=\frac{1}{2}\Delta q_{QM}(x)$, which means that one can decompose the quark model spin contribution $\Delta q_{QM}(x)$ by a quark helicity term $\Delta q(x)$ {\it plus} an orbital angular momentum term $L_q(x)$. There is also a new relation connecting the quark orbital angular momentum with the measurable quark helicity distribution and transversity distribution ($\delta q(x)$): $\Delta q(x)+L_q(x)=\delta q(x)$, from which we may have new sum rules connecting the quark orbital angular momentum with the nucleon axial and tensor charges.

20 latex pages, including an eps figure, to appear in Phys. Rev. D

References in corpus (5)

• Quantum Chromodynamics and Other Field Theories on the Light Cone
• Polarised Quark Distributions in the Nucleon from Semi-Inclusive Spin Asymmetries
• Melosh rotation: source of the proton's missing spin
• The Intrinsic Gluon Component of the Nucleon
• A positivity bound for the longitudinal gluon distribution in a nucleon

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