Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constraints on the polarized gluon density in the proton from charm
  photoproduction   We consider the possibility of a direct determination of the polarized gluon
density in the proton using charm production with polarized beams at HERA. We
study total cross sections and distributions at leading order using different
parametrizations of the polarized gluon density. We conclude that charm
photoproduction data can be used to constrain the polarized gluon density in
the proton if an integrated luminosity of 100~pb$^{-1}$ will be achieved at
HERA.

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The categories of this paper are: nucl-th
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The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
19
The categories of this paper are: eess
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
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The categories of this paper are: astro-ph
27
The categories of this paper are: comp-gas