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arXiv · hep-ph/9912289

Quark Orbital Angular Momentum from Lattice QCD

N. Mathur·S. J. Dong·K. F. Liu·L. Mankiewicz·N. C. Mukhopadhyay
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Abstract

We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the $Z_2$ noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be $0.30 \pm 0.07$. From this and the quark spin content we deduce the quark orbital angular momentum to be $0.17 \pm 0.06$ which is $\sim 34$% of the proton spin. We further predict that the gluon angular momentum to be $0.20 \pm 0.07$, i. e. $\sim$ 40% of the proton spin is due to the glue.

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N. Mathur, S. J. Dong, K. F. Liu, L. Mankiewicz, N. C. Mukhopadhyay. 1999-12-10. Quark Orbital Angular Momentum from Lattice QCD. https://doi.org/10.1103/physrevd.62.114504

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