Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unintegrated parton distributions and pion production in pp collisions
  at RHIC's energies   We compare results of $2 \to 1$ $k_t$-factorization approach with
Kwieci\'nski unintegrated parton distributions and the standard collinear
factorization approach at RHIC and slightly smaller energies. Our approach
contains only one free parameter responsible for internal parton motion in
nucleons. In contrast to recent works in the literature our $k_t$-factorization
approach includes also quark degrees of freedom in addition to purely gluonic
terms. Both mid and forward rapidity regions are considered. We discuss
uncertainties due to fragmentation functions. In general, the
$k_t$-factorization approach gives a better description of the $p_t \sim$ 1 --
4 GeV region both at mid and forward rapidity regions. Our approach leads to
asymmetry in the production of $\pi^+$ and $\pi^-$, very similar to the one
observed very recently by the BRAHMS collaboration.

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The categories of this paper are: chem-ph
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The categories of this paper are: physics
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The categories of this paper are: q-alg
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: stat
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The categories of this paper are: adap-org
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The categories of this paper are: acc-phys
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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: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas