Results on Identified Charged Hadrons from the PHENIX Experiment at RHIC

Recent results on identified hadrons from the PHENIX experiment in Au+Au collisions at mid-rapidity at $\sqrt{s_{NN}}$ = 200 GeV are presented. The centrality dependence of transverse momentum distributions and particle ratios for identified charged hadrons are studied.Comment: 10pp. To appear in the proceedings of The XVI International Conference on Particles and Nuclei (PaNic02), Osaka, Japan, September 30 - October 4, 200

High p_T identified hadron ratios in sqrt(s_NN)=200GeV Au+Au Collisions

The PHENIX detector at RHIC measured high p_T identified hadron ratios in sqrt(s_NN) = 200GeV Au+Au collisions. Within the current systematic and statistical errors, pbar/p ratios that are measured up to 3.8GeV/c are almost independent of both p_T and centrality. The baryon to meson ratio is measured through p/pi and pbar/pi ratios up to 3.8GeV/c, showing they are strongly centrality dependent.Comment: 4 pages, 4 figures. Talk presented at Quark Matter 2002, Nantes, France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A

Results on Identified Hadrons from the PHENIX Experiment at RHIC

Recent results on identified hadrons from the PHENIX experiment in Au+Au collisions at mid-rapidity at $\sqrt{s_{NN}}$ = 200 GeV are presented. The centrality dependence of transverse momentum distributions and particle ratios for identified charged hadrons are studied. The transverse flow velocity and freeze-out temperature are extracted from $p_{T}$ spectra within the framework of a hydrodynamic collective flow model. Two-particle HBT correlations for charged pions are measured in different centrality selections for a broad range of transverse momentum of the pair. Results on elliptic flow measurements with respect to the reaction plane for identified particles are also presented.Comment: 10 pages, 10 figures. Talk presented at Quark Matter 2002, Nantes, France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A

High pTp_{T} Inclusive Charged Hadron Spectra from Au+Au Collisions at sNN\sqrt{s_{NN}} = 200 GeV

The STAR Collaboration presents new measurements of inclusive charged hadron distributions for $p_{T} <$ 12 GeV/c from Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. Charged hadron suppression at high $p_{T}$ is similar in shape and magnitude at all centralities to that observed previously at $\sqrt{s_{NN}}$ = 130 GeV for $p_{T} <$ 6 GeV/c. The ratio of spectra from central and peripheral Au+Au collisions shows that hadron suppression is approximately constant within 6 $< p_{T} <$ 12 GeV/c. The ratios of charged hadron spectra at the two beam energies show a 15-20% increase in yield at low $p_{T}$. At high $p_{T}$, the ratios show a larger increase that agrees well with pQCD calculations of the $\sqrt{s_{NN}}$ dependence of particle production in Au+Au collisions.Comment: 4 pages, 4 figures, Quark Matter 2002 Proceeding

Charge Particle Multiplicity and Transverse Energy Measurements in Au-Au collisions in PHENIX at RHIC

We present results on charged particle and transverse energy densities measured at mid-rapidity in Au-Au collisions at sqrt(s_{NN})=200 GeV. The mean transverse energy per charged particle is derived. The results are presented as a function of centrality, which is defined by the number of participating nucleons, and compared to results obtained in Au-Au collisions at sqrt{s_{NN})=130 GeV. A comparison with calculations from various theoretical models is performed.Comment: 4 pages, 5 figures. Talk presented at Quark Matter 2002, Nantes, France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A

Dynamics of Particle Production in Relativistic Nuclear Collisions

Saturation models for particle production in relativistic nuclear collisions are discussed. In particular, I show that the predictions from the high density QCD for the qualitative shape of $dN/dy$ are very sensitive to the form of the unintegrated gluon distribution.Comment: 4 pages, 4 figures, Proceedings for Quark Matter 200

Source Parameters from Identified Hadron Spectra and HBT Radii for Au-Au Collisions at sqrt(s_NN)=200 GeV in PHENIX

The characteristics of the particle emitting source are deduced from low transverse momentum identified hadron spectra (transverse mass less than 1 GeV) and HBT radii using a hydrodynamic interpretation. From the most peripheral to the most central data, the single particle spectra are fit simultaneously for all pions, kaons, and (anti-)protons using the parameterization in [1] and assuming a linear transverse flow profile. Within the systematic uncertainties, the expansion parameters called the freeze-out temperature and flow velocity, respectively decrease and increase with the number of participants, saturating for both at mid-centrality. The expansion using analytic calculations of the kT dependence of HBT radii in [2] is fit to the data but no chi-squared minimum is found.Comment: 4 pages, 4 figures, Contribution to Quark Matter 2002, Nantes, France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A

Jet Fragmentation in Vacuum and Medium with gamma-hadron Correlations in PHENIX

Jet fragmentation in p+p and Au+Au collisions is studied via back-to-back correlations of direct photons and charged hadrons. The direct photon correlations are obtained by statical subtraction of the background from decay photons. Results on the nuclear modification to the associated charged hadron yields are reviewed. Further studies of jet fragmentation in p+p using isolated direct photons are also presented. A kT-smeared LO pQCD calculation is used to interpret the data. The sensitivity of the data to the underlying fragmentation function is tested and the results are found to be compatible with expectations of a sample dominated by quark jet fragmentation.Comment: Talk presented at Hot Quarks 2010, June 21-26, La Londe Les Maures, France. To be published in Journal of Physics: Conference Series (JPCS

High-p_T pi^0 suppression in Au+Au collisions at sqrt(s_NN) = 200 GeV

Neutral pions with p_T = 1 - 8 GeV/c have been measured for 9 different centrality classes in Au+Au collisions at sqrt(s_NN) = 200 GeV by the PHENIX experiment at RHIC. The pi^0 multiplicity in central reactions is significantly below the binary collision scaled yields from both peripheral Au+Au and pp reactions. The observed suppression sets in for the 50-70% centrality class and increases with p_T and centrality. For the most central bin, the deficit amounts to a factor ~2.5 at p_T ~ 2 GeV/c gradually increasing to a factor ~6 at p_T ~ 8 GeV/c.Comment: 4 pages, 4 figures. Talk given at Quark Matter 2002 (QM 2002), Nantes, Bretagne, France, 18-24 Jul 2002. Minor corrections in tex

What can we learn from hydrodynamic analysis at RHIC?

We can establish a new picture, the perfect fluid sQGP core and the dissipative hadronic corona, of the space-time evolution of produced matter in relativistic heavy ion collisions at RHIC. It is also shown that the picture works well also in the forward rapidity region through an analysis based on a new class of the hydro-kinetic model and that this is a manifestation of rapid increase of entropy density in the vicinity of QCD critical temperature, namely deconfinement.Comment: 8 pages, 4 figures, talk given at Workshop on Quark-Gluon-Plasma Thermalization, Vienna, Austria, 10-12 Aug 200