Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Boer-Mulders function of the pion in the MIT bag model   We apply the MIT bag model to study the Boer-Mulders function of the pion, a
$T$-odd function that describes the transverse polarization distribution of the
quark inside the pion. We simulate the effect of the gauge link through the
"one-gluon-exchange" approximation. We consider both the quark helicity nonflip
and double-flip contributions. The result in the MIT bag model is compared with
those in the spectator models.

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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
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The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: astro-ph