Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gluon Polarisation in the Nucleon and Longitudinal Double Spin
  Asymmetries from Open Charm Muoproduction   The gluon polarisation in the nucleon has been determined by detecting charm
production via D0 meson decay to charged K and pi in polarised muon scattering
off a longitudinally polarised deuteron target. The data were taken by the
COMPASS Collaboration at CERN between 2002 and 2006 and corresponds to an
integrated luminosity of 2.8 fb^-1. The dominant underlying process of charm
production is the photon-gluon fusion to a cc-bar pair. A leading order QCD
approach gives an average gluon polarisation of (Delta g/g)_x= -0.49 +-
0.27(stat) +- 0.11(syst) at a scale mu^2 ~ 13 (GeV/c)^2 and at an average gluon
momentum fraction (x) ~ 0.11. The longitudinal cross-section asymmetry for D0
production is presented in bins of the transverse momentum and the energy of
the D0 meson.

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The categories of this paper are: hep-th
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The categories of this paper are: astro-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
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The categories of this paper are: mtrl-th
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The categories of this paper are: eess