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The Gluon Spin in the Chiral Bag Model

H. -J. Lee·D. -P. Min·B. -Y. Park·M. Rho·V. Vento
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Abstract

We study the gluon polarization contribution at the quark model renormalization scale to the proton spin, $Γ$, in the chiral bag model. It is evaluated by taking the expectation value of the forward matrix element of a local gluon operator in the axial gauge $A^+=0$. It is shown that the confining boundary condition for the color electric field plays an important role. When a solution satisfying the boundary condition for the color electric field, which is not the conventionally used but which we favor, is used, the $Γ$ has a positive value for {\it all} bag radii and its magnitude is comparable to the quark spin polarization. This results in a significant reduction in the relative fraction of the proton spin carried by the quark spin, which is consistent with the small flavor singlet axial current measured in the EMC experiments.

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H. -J. Lee, D. -P. Min, B. -Y. Park, M. Rho, V. Vento. 2000-06-05. The Gluon Spin in the Chiral Bag Model. https://doi.org/10.1016/s0370-2693(00)01054-6

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