Centrality and pseudorapidity dependence of elliptic flow for charged hadrons in Au+Au collisions at sqrt(sNN) = 200 GeV

This paper describes the measurement of elliptic flow for charged particles in Au+Au collisions at sqrt(sNN)=200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). The measured azimuthal anisotropy is presented over a wide range of pseudorapidity for three broad collision centrality classes for the first time at this energy. Two distinct methods of extracting the flow signal were used in order to reduce systematic uncertainties. The elliptic flow falls sharply with increasing eta at 200 GeV for all the centralities studied, as observed for minimum-bias collisions at sqrt(sNN)=130 GeV.Comment: Final published version: the most substantive change to the paper is the inclusion of a complete description of how the errors from the hit-based and track-based analyses are merged to produce the 90% C.L. errors quoted for the combined results shown in Fig.

Centrality Dependence of Charged Particle Multiplicity at Mid-Rapidity in Au+Au Collisions at sqrt(s_NN) = 130 GeV

We present a measurement of the pseudorapidity density of primary charged particles near mid-rapidity in Au+Au collisions at sqrt(s_NN) = 130 GeV as a function of the number of participating nucleons. These results are compared to models in an attempt to discriminate between competing scenarios of particle production in heavy ion collisions.Comment: 5 pages, 4 figures, revtex (submitted to Phys. Rev. Letters

Forward-Backward Multiplicity Correlations in sqrt(s_NN) = 200 GeV Gold-Gold Collisions

Forward-backward correlations of charged-particle multiplicities in symmetric bins in pseudorapidity are studied in order to gain insight into the underlying correlation structure of particle production in Au+Au collisions. The PHOBOS detector is used to measure integrated multiplicities in bins centered at eta, defined within |eta|<3, and covering intervals Delta-eta. The variance sigma^2_C of a suitably defined forward-backward asymmetry variable C is calculated as a function of eta, Delta-eta, and centrality. It is found to be sensitive to short range correlations, and the concept of "clustering'' is used to interpret comparisons to phenomenological models.Comment: 5 Pages, 5 Figures, submitted to Physical Review C -- Rapid Communication

Rapidity and k_T dependence of HBT correlations in Au+Au collisions at 200 GeV with PHOBOS

Two-particle correlations of identical charged pion pairs from Au+Au collisions at sqrt(s_NN) = 200 GeV were measured by the PHOBOS experiment at RHIC. Data for the most central (0--15%) events were analyzed with Bertsch-Pratt (BP) and Yano-Koonin-Podgoretskii (YKP) parameterizations using pairs with rapidities of 0.4 < y < 1.3 and transverse momenta 0.1 < k_T < 1.4 GeV/c. The Bertsch-Pratt radii decrease as a function of pair transverse momentum. The pair rapidity Y_pipi roughly scales with the source rapidity Y_YKP, indicating strong dynamical correlations.Comment: 5 pages, 2 figures. To appear in the proceedings of Seventeenth International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland, California from January 11-17, 2004. Submitted to Journal of Physics G: Nuclear and Particle Physic

Identified particles in Au+Au collisions at sqrt{s_NN} = 200 GeV

The yields of identified particles have been measured at RHIC for Au+Au collisions at sqrt{s_NN} = 200 GeV using the PHOBOS spectrometer. The ratios of antiparticle to particle yields near mid-rapidity are presented. The first measurements of the invariant yields of charged pions, kaons and protons at very low transverse momenta are also shown.Comment: 4 pages, 4 figures, Contribution to Quark Matter 2002, Nantes, France, July 200

Elliptic Flow in Au+Au Collisions at RHIC

Elliptic flow is an interesting probe of the dynamical evolution of the dense system formed in the ultrarelativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC). The elliptic flow dependences on transverse momentum, centrality, and pseudorapidity were measured using data collected by the PHOBOS detector, which offers a unique opportunity to study the azimuthal anisotropies of charged particles over a wide range of pseudorapidity. These measurements are presented, together with an overview of the analysis methods and a discussion of the results.Comment: Presented at Hot Quarks 2004; 7 pages, 6 figure

Recent Results from PHOBOS at RHIC

The PHOBOS experiment at RHIC has recorded measurements for Au-Au collisions spanning nucleon-nucleon center-of-mass energies from 19.6 GeV to 200 GeV. Global observables such as elliptic flow and charged particle multiplicity provide important constraints on model predictions that characterize the state of matter produced in these collisions. The nearly 4 pi acceptance of the PHOBOS experiment provides excellent coverage for complete flow and multiplicity measurements. Results including beam energy and centrality dependencies are presented and compared to elementary systems.Comment: 4 pages, 4 figures, proceedings from PANIC02 in Osaka, Japa

The Landscape of Particle Production: Results from PHOBOS

Recent results from the PHOBOS experiment at RHIC are presented, both from Au+Au collisions from the 2001 run and p+p and d+Au collisions from 2003. The centrality dependence of the total charged particle multiplicity in p+p and d+Au show features, such as Npart-scaling and limiting fragmentation, similar to p+A collisions at lower energies. Multiparticle physics in Au+Au is found to be local in (pseudo)rapidity, both when observed by HBT correlations and by forward-backward pseudorapidity correlations. The shape of elliptic flow in Au+Au, measured over the full range of pseudorapidity, appears to have a very weak centrality dependence. Identified particle ratios in d+Au reactions show little difference between the shape of proton and anti-proton spectra, while the absolute yields show an approximate m_T scaling.Comment: 8 Pages, 11 Figures, Plenary talk at Quark Matter 2004, Oakland, CA, January 11-18, 200

Ratios of charged antiparticles to particles near mid-rapidity in Au+Au collisions at sqrt(s_NN) = 130 GeV

We have measured the ratios of antiparticles to particles for charged pions, kaons and protons near mid-rapidity in central Au+Au collisions at sqrt(s_NN) = 130 GeV. For protons, we observe pbar/p = 0.60 +/- 0.04 (stat.) +/- 0.06 (syst.) in the transverse momentum range 0.15 < p_T < 1.0 GeV/c. This leads to an estimate of the baryo-chemical potential mu_B of 45 MeV, a factor of 5-6 smaller than in central Pb+Pb collisions at sqrt(s_NN) = 17.2 GeV.Comment: 4 page