Figure. The < Nbinary> -scaled ratio of hadron yields in central
peripheral Au+Au collisions, RCP, for two centrality classes as
a function of pT. The
curves are theoretical model comparisons.
Transverse momentum and collision energy dependence of high pT hadron suppression in Au+Au collisions at RHIC
The < Nbinary> -scaled ratio of particle yields in
central relative to
peripheral collisions, RCP is similar to RAB and also
large suppression of inclusive hadron production in central collisions.
The observed factor of 5
suppression in central collisions was shown by these high precision
measurements to be independent of pT
for 6 < pT < 12 GeV/c.
We compared the STAR measurements to the results of three theoretical
calculations: two models
based on pQCD incorporating shadowing, the Cronin effect and jet
quenching in dense matter (pQCD-I, pQCD-II) and a model incorporating gluon
in the incoming Au nuclei. The pQCD-based calculations contain one free
parameter, the energy density for central collisions, which is fit to
the data, yielding an initial density 30-50 times that of cold nuclear
matter. These calculations then successfully
describe the pT and centrality dependence of the inclusive
suppression for pT > 5 GeV/c. The saturation model also describes the
suppression and its pT-dependence for the 0-5%/40-60% ratio for
pT > 5 GeV/c.
These precision STAR data on inclusive charged hadron
suppression, covering wide centrality and kinematic range, are
well-described by widely differing models which attribute the
suppression either to jet quenching in dense matter in the final state
or to gluon saturation in the initial state. The resolution of this
ambiguity requires the isolation of
initial state nuclear effects in d+Au collisions.
Related STAR papers
Transverse momentum and collision energy dependence of high pT hadron suppression in Au+Au collisions at ultrarelativistic energies
Phys. Rev. Lett. 91 (2003) 172302
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