30 research outputs found
Systematics of Global Observables in Cu+Cu and Au+Au Collisions at RHIC Energies
Charged particles produced in Cu+Cu collisions at \sqrt{s_{NN}} = 200 and
62.4 GeV have been measured in the PHOBOS experiment at RHIC. The comparison of
the results for Cu+Cu and Au+Au for the most central collisions at the same
energy reveals that the particle density per nucleon participant pair and the
extended longitudinal scaling behavior are similar in both systems. This
implies that for the most central events in symmetric nucleus-nucleus
collisions the particle density per nucleon participant pair does not depend on
the size of the two colliding nuclei but only on the collision energy. Also the
extended longitudinal scaling seems independent of the colliding energy and
species for central collisions. In addition, there is an overall factorization
of dN/dEta shapes as a function of collision centrality between Au+Au and Cu+Cu
collisions at the same energy.Comment: 3 pages, 2 figures. Contributed talk at PANIC '05 conference, Santa
Fe, NM, Oct 24-28, 200
Probing properties of hot and dense QCD matter with heavy flavor in the PHENIX experiment at RHIC
Hadrons carrying heavy quarks, i.e. charm or bottom, are important probes of the hot and dense medium created in relativistic heavy ion collisions. Heavy quarkantiquark pairs are mainly produced in initial hard scattering processes of partons. While some of the produced pairs form bound quarkonia, the vast majority hadronize into particles carrying open heavy flavor. Heavy quark production has been studied by the PHENIX experiment at RHIC via measurements of single leptons from semi-leptonic decays in both the electron channel at mid-rapidity and in the muon channel at forward rapidity. A large suppression and azimuthal anisotropy of single electrons have been observed in Au + Au collisions at 200 GeV. These results suggest a large energy loss and flow of heavy quarks in the hot, dense matter. The PHENIX experiment has also measured J/ψ production at 200 GeV in p + p, d + Au, Cu + Cu and Au + Au collisions, both at mid- and forward-rapidities, and additionally Cu + Au and U + U at forward-rapidities. In the most energetic collisions, more suppression is observed at forward rapidity than at central rapidity. This can be interpreted either as a sign of quark recombination, or as a hint of additional cold nuclear matter effects. The centrality dependence of nuclear modification factor, RAA(pT), for J/ψ in U + U collisions at √sNN = 193 GeV shows a similar trend to the lighter systems, Au + Au and Cu + Cu, at similar energy 200 GeV
Elliptic Flow and Initial Eccentricity in Cu+Cu and Au+Au Collisions at RHIC
We present a systematic study of elliptic flow as a function of centrality,
pseudorapidity, transverse momentum and energy for Cu+Cu and Au+Au collisions
from the PHOBOS experiment. New data on elliptic flow in Cu+Cu collisions at
22.4 GeV are shown. Elliptic flow scaled by participant eccentricity is found
to be similar for both systems when collisions with the same number of
participants or the same average area density are compared. This similarity is
observed over a wide range in pseudorapidity and transverse momentum,
indicating that participant eccentricity is the relevant quantity for
generating the azimuthal asymmetry leading to the observed elliptic flow.Comment: 5 pages, 4 figures, the 19th International Conference On Ultra
relativistic Nucleus-Nucleus Collisions (Quark Matter 2006), Shanghai China,
Nov. 14-20, 200