Figure. (a) The ratio of hadron production in d+Au and Au+Au to p+p collisions as a
function of pT.
(b) The azimuthal angular correlation of pairs of high pT
hadrons in p+p, d+Au, and central Au+Au
collisions.
|
Evidence from d+Au measurements for final-state suppression of high pT hadrons in Au+Au collisions at RHIC
The factor of five suppression of high pT hadron production
and the suppression of away-side jets in
central Au+Au collisions compared to proton+proton collisions are some of
the most exciting results
produced by STAR. The interpretation of these effects as due to
final-state
interactions of jets in the dense matter formed in the collision requires
the demonstration that such effects
do not occur in high energy nuclear collisions in which no medium is
formed. The d+Au collisions from RHIC
Run-III provide such a testing ground.
The top panel of the figure shows the ratio of hadron production in d+Au
and Au+Au collisions to that in
p+p collisions, scaled to account for the nuclear geometry, as a function
of pT. High pT hadron production
is enhanced in d+Au collisions (R_AB>1), similar to the Cronin enhancement
observed in experiments at lower
energies, in contrast to the results from Au+Au collisions where only 20%
of the expected hadrons are
observed.
The lower panel shows the azimuthal angular correlation of pairs of high
transverse momentum
particles in p+p, d+Au and central Au+Au collision. The peaks seen at
small angular separation are
characteristic of jet production, while those seen at 180 degrees in p+p
and d+Au are characteristic of
di-jets. The absence of the second peak in Au+Au collisions demonstrates
that the second jet has been
absorbed by the medium created in the collisions. These pieces taken
together provide strong evidence
that the density of the medium generated in central Au+Au collisions is
many times that of cold nuclear
matter.
Related STAR papers
Evidence from d+Au measurements for final-state suppression of high pT hadrons in Au+Au collisions at RHIC
Phys. Rev. Lett. 91 (2003) 072304
e-Print Archives (nucl-ex/0306024):
Abstract |
PS |
PDF
Journal article:
Phys. Rev. Lett. server
Centrality Dependence of High pT Hadron Suppression in Au + Au Collisions at sqrt(snn) = 130 GeV
Phys. Rev. Lett. 89 (2002) 202301
e-Print Archives (nucl-ex/0206011):
Abstract |
PS |
PDF
Journal article:
Phys. Rev. Lett. server
Disappearance of back-to-back high pT hadron correlations in central Au + Au collisions at sqrt(snn) = 200 GeV
Phys. Rev. Lett. 90 (2003) 082302
e-Print Archives (nucl-ex/0210033):
Abstract |
PS |
PDF
Journal article:
Phys. Rev. Lett. server
| 
