Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Charged Particle Multiplicities in Ultra-relativistic Au+Au and Cu+Cu
  Collisions   The PHOBOS collaboration has carried out a systematic study of charged
particle multiplicities in Cu+Cu and Au+Au collisions at the Relativistic
Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. A unique feature
of the PHOBOS detector is its ability to measure charged particles over a very
wide angular range from 0.5 to 179.5 deg. corresponding to |eta|<5.4. The
general features of the charged particle multiplicity distributions as a
function of pseudo-rapidity, collision energy and centrality, as well as system
size, are discussed.

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The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
10
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: q-alg
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The categories of this paper are: eess
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The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas