System size dependence of cluster properties from two-particle angular correlations in Cu+Cu and Au+Au collisions at sq root(s{sub NN})=200 GeV

Journal Article · Mon Feb 15 00:00:00 EST 2010 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.81.024904· OSTI ID:21386622

Alver, B; Ballintijn, M; Busza, W; Gulbrandsen, K; Henderson, C; Kane, J L; Kulinich, P; Li, W; Loizides, C; Reed, C; Roland, C; Roland, G; Stephans, G S. F.; Nieuwenhuizen, G J. van; Vaurynovich, S S; Verdier, R; Veres, G I; Wenger, E; Wyslouch, B ^[1]; Back, B B ^[2]

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1. Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States)
2. Argonne National Laboratory, Argonne, Illinois 60439-4843 (United States)

We present results on two-particle angular correlations in Cu+Cu and Au+Au collisions at a center-of-mass energy per nucleon pair of 200 GeV over a broad range of pseudorapidity (eta) and azimuthal angle (phi) values as a function of collision centrality. The PHOBOS detector at the Relativistic Heavy Ion Collider 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 in {Delta}{eta} and {Delta}{phi} emerges, which is interpreted in the context of a cluster model. The effective cluster size and decay width are extracted from the two-particle pseudorapidity correlation functions. The effective cluster size found in semicentral Cu+Cu and Au+Au collisions is comparable to that found in proton-proton collisions but a nontrivial decrease in size with increasing centrality is observed. Moreover, a comparison of results from Cu+Cu versus Au+Au collisions shows an interesting scaling of the effective cluster size with the measured fraction of total cross section (which is related to the ratio of the impact parameter to the nuclear radius, b/2R), suggesting a geometric origin. Further analysis for pairs from restricted azimuthal regions shows that the effective cluster size at {Delta}{phi}{approx}180 deg. drops more rapidly toward central collisions than the size at {Delta}{phi}{approx}0 deg. The effect of limited {eta} acceptance on the cluster parameters is also addressed, and a correction is applied to present cluster parameters for full {eta} coverage, leading to much larger effective cluster sizes and widths than previously noted in the literature. These results should provide insight into the hot and dense medium created in heavy ion collisions.

• OSTI ID: 21386622
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 81, Issue 2; Other Information: DOI: 10.1103/PhysRevC.81.024904; (c) 2010 The American Physical Society; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ANGULAR CORRELATION
ATOM-ATOM COLLISIONS
BROOKHAVEN RHIC
CHARGED PARTICLES
CLUSTER MODEL
COLLISIONS
COMPARATIVE EVALUATIONS
COPPER
CORRECTIONS
CORRELATION FUNCTIONS
GEV RANGE 100-1000
GOLD
HEAVY ION REACTIONS
IMPACT PARAMETER
MASS
NUCLEONS
PROTON-PROTON INTERACTIONS
TOTAL CROSS SECTIONS
TWO-DIMENSIONAL CALCULATIONS
ACCELERATORS
ATOM COLLISIONS
BARYON-BARYON INTERACTIONS
BARYONS
CORRELATIONS
CROSS SECTIONS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY RANGE
EVALUATION
FERMIONS
FUNCTIONS
GEV RANGE
HADRON-HADRON INTERACTIONS
HADRONS
HEAVY ION ACCELERATORS
INTERACTIONS
MATHEMATICAL MODELS
METALS
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEON-NUCLEON INTERACTIONS
PARTICLE INTERACTIONS
PROTON-NUCLEON INTERACTIONS
STORAGE RINGS
TRANSITION ELEMENTS