38 research outputs found
Characteristics of Parton Energy Loss Studied with High-p_T Particle Spectra from PHENIX
In the first three years of the physics program at the Relativistic Heavy Ion
Collider (RHIC) a picture was established in which the suppression of hadrons
at high transverse momenta (p_T) in central Au+Au collisions is explained by
energy loss of quark and gluon jets in a medium of high color-charge density.
Measurements of single particle spectra for a smaller nucleus (Cu), for
different center-of-mass energies and with higher statistics were performed in
the subsequent years and are used to test predictions and assumptions of jet
quenching models in more detail. The measurements presented here are consistent
with a parton energy loss scenario so that these models can be used to relate
the observed suppression to properties of the created medium.Comment: To appear in the proceedings of 20th International Conference on
Ultra-Relativistic Nucleus-Nucleus Collisions: Quark Matter 2008 (QM2008),
Jaipur, India, 04-10 Feb 200
Are High-pT Pions Suppressed in Pb+Pb Collisions at sqrt(sNN) = 17.3 GeV?
Transverse momentum spectra of neutral pions in the range 0.7 < pT < 3.2
GeV/c have been measured at 2.3 < eta < 3.0 by the WA98 experiment in p+C and
p+Pb collisions at sqrt(sNN) = 17.3 GeV. Scaled by the number of
nucleon-nucleon collisions (Ncoll) the pi^0 yields in p+C and p+Pb at pT ~ 2.0
- 2.5 GeV/c are higher than the respective yields in central Pb+Pb collisions
with Npart > 300. This observation is qualitatively consistent with
expectations from parton energy loss.Comment: 4 pages, 3 figures, To appear in the proceedings of the Quark Matter
2006 conference, Shanghai, China, 14-20 Nov 200
Interferometry of direct photons in Pb+Pb collisions at 158 AGeV
We present final results from the WA98 experiment which provide first
measurements of Bose-Einstein correlations of direct photons in
ultrarelativistic heavy ion collisions. Invariant interferometric radii were
extracted in the range MeV/c and compared to interferometric
radii of charged pions. The yield of direct photons for MeV/c was
extracted from the correlation strength parameter and compared to the yield of
direct photons measured in WA98 at higher with the statistical
subtraction method, and to predictions of a fireball model.Comment: 4 pages, 3 figures, proceedings for Quark Matter 200
Event anisotropy in 4.2A GeV/c C+C collisions
The directed and elliptic flow of protons and negative pions in 4.2A GeV/c
C+C collisions is studied using the Fourier analysis of azimuthal
distributions. It is found that the protons exhibit pronounced directed flow,
while the flow of pions is either non existent or too weak to be detected
experimentally. Also, it is found that in the entire rapidity interval the
elliptic flow is very small if not zero. These results are confirmed by the
Quark-Gluon-String Model (QGSM) and the relativistic transport model (ART 1.0),
except that these models predict very weak antiflow of pions. The more detailed
comparison with the QGSM suggests that the decay of resonances and rescattering
of secondaries dominantly determine the proton and negative pion flow at this
energy.Comment: 7 pages, 3 figures, TeX file changed from double to single-spacin