Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Single Spin Asymmetry in Inclusive Pion Production, Collins Effect and
  the String Model (revised version)   We calculated the single spin asymmetry in the inclusive pion production in
the fragmentation region of transversely polarized proton-proton collisions. We
generated the asymmetry at the level of fragmentation function (Collins effect)
by the Lund coloured string mechanism. We compared our results to the presently
available experimental data. We obtained a qualitative agreement with the data
after assuming that the transverse polarizations of the $u$ and the $d$ quarks
in the proton are +1 and -1, respectively, at x_B = 1.

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The categories of this paper are: acc-phys
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The categories of this paper are: econ
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con
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The categories of this paper are: adap-org