  We present results on two-particle angular correlations in p+p and Cu+Cu
collisions over a broad range of ($\eta$,$\phi$). The PHOBOS detector has a
uniquely large angular coverage for inclusive charged particles. This allows
for the study of correlations on both long and short range pseudorapidity
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.
Relative to p+p collisions, Cu+Cu reactions show a non-trivial decrease of
cluster size with increasing centrality. These results may provide insight into
the hadronization stage of the hot and dense medium created in heavy ion
collisions.
