Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Single target-spin asymmetries in semi-inclusive pion electroproduction
  on longitudinally polarized protons   We evaluate the single target-spin sin(phi_h) and sin(2\phi_h) azimuthal
asymmetries in the semi-inclusive deep inelastic lepton scattering off
longitudinally polarized proton target under HERMES kinematic conditions. A
good agreement with the HERMES data can be achieved using only the twist-2
distribution and fragmentation functions.

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The categories of this paper are: physics
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The categories of this paper are: hep-th
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The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
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The categories of this paper are: stat
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The categories of this paper are: cond-mat
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The categories of this paper are: cs
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin