Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: System size dependence of two-particle angular correlations in p+p,
  Cu+Cu and Au+Au collisions   We present a systematic study of two-particle angular correlations in p+p,
Cu+Cu and Au+Au collisions over a broad range of pseudorapidity and azimuthal
angle. The PHOBOS detector has a uniquely large angular coverage for inclusive
charged particles, which allows for the study of correlations on both long- and
short-range scales. A complex two-dimensional correlation structure emerges
which is interpreted in the context of a cluster model. The cluster size and
its decay width are extracted from the two-particle pseudorapidity correlation
function. The cluster size found in semi-central Cu+Cu and Au+Au collisions is
comparable to that found in p+p but a non-trivial increase of cluster size with
decreasing centrality is observed. Moreover, the comparison between Cu+Cu and
Au+Au systems shows an interesting scaling of the cluster size with the
measured fraction of total cross section (which is related to $b/2R$),
suggesting a geometric origin. These results should provide insight into the
hadronization stage of the hot and dense medium created in heavy ion
collisions.

6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th