Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of pi0 and eta Mesons with PHENIX in sqrt(s_NN) = 200 GeV
  Au+Au Collisions at RHIC   The pi0 meson has been a crucial proble for observing jet quenching in
ultrarelativistic heavy-ion collisions at RHIC. Measurements of the eta meson
in the same collisions have also shed light on a possible dependence of the
observed suppression on the particle species. The preliminary pi0 nuclear
modification factor R_AA from the 2004 RHIC run allowed a first systematic
comparison between a precise measurement with high statistics and theoretical
calculations, constraining model parameters such as the initial gluon density
dN^g/dy, and the transport coefficient qhat. The final pi0 spectra and R_AA are
shown as well as the first eta results obtained with both PHENIX
electromagnetic calorimeters.

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The categories of this paper are: chem-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: astro-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: math
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The categories of this paper are: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: nlin
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The categories of this paper are: q-bio