Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quark orbital motions from Wigner distributions   We investigate quark Wigner distributions in a light-cone spectator model.
Both the scalar and the axial-vector spectators are included. The light-cone
wave functions are derived from effective quark-spectator-nucleon vertex and
then generalized by adjusting the power of energy denominators. The gauge link
is taken into account by introducing relative phases to the light-cone
amplitudes, and the phases are estimated from one gluon exchange interactions.
The mixing distributions, which describe the correlation between transverse
coordinate and transverse momentum and represent quark orbital motions, are
calculated from the Wigner distributions. We find both $u$ quark and $d$ quark
have positive orbital angular momentum in a polarized proton at small $x$
region, but a sign change is observed at large $x$ region for the $d$ quark.
Besides, some model relations between Wigner distributions with different
polarization configurations are found.

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The categories of this paper are: q-bio
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: math
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
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The categories of this paper are: astro-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: dg-ga
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The categories of this paper are: cond-mat
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The categories of this paper are: bayes-an
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The categories of this paper are: physics
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The categories of this paper are: acc-phys
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The categories of this paper are: econ