Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universal Behavior of Charged Particle Production in Heavy Ion
  Collisions at RHIC Energies   The PHOBOS experiment at RHIC has measured the multiplicity of primary
charged particles as a function of centrality and pseudorapidity in Au+Au
collisions at sqrt(s_NN) = 19.6, 130 and 200 GeV. Two kinds of universal
behavior are observed in charged particle production in heavy ion collisions.
The first is that forward particle production, over a range of energies,
follows a universal limiting curve with a non-trivial centrality dependence.
The second arises from comparisons with pp/pbar-p and e+e- data.
N_tot/(N_part/2) in nuclear collisions at high energy scales with sqrt(s) in a
similar way as N_tot in e+e- collisions and has a very weak centrality
dependence. This feature may be related to a reduction in the leading particle
effect due to the multiple collisions suffered per participant in heavy ion
collisions.

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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: atom-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
3
The categories of this paper are: physics
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The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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The categories of this paper are: cond-mat