Centrality dependence of the N(Ω)/N(ϕ)N(\Omega)/N(\phi) ratios and ϕ\phi v2v_{2} - a test of thermalization in Au+Au collisions at RHIC

We present the centrality dependence of the $N(\Omega)/N(\phi)$ ratios and $\phi$ $v_{2}$ measured in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by the STAR experiment at RHIC. The results are compared to measurements of other identified particles and recombination model expectations in order to gain insight into the partonic collectivity and possible thermalization of the produced medium.Comment: 4 pages, 2 figures, Quark Matter 2006 conference proceeding

Phi-meson Production in Heavy-Ion Collisions at RHIC

We present the first elliptic flow, $v_{2}$, measurement for the $\phi$-meson in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. At low $p_{T}$ (<2 GeV/c), the $v_{2}$ is consistent with mass ordering expected from hydrodynamics, while at higher $p_{T}$ (>4 GeV/c), it follows the same trend as the $K^{0}_{S}$ $v_{2}$ and a parameterization for number of quarks = 2. The nuclear modification factor, $R_{CP}$, has also been measured and it follows the same trend as the $K^{0}_{S}$ rather than the $\Lambda$ which confirms the baryon/meson-type dependence of $R_{CP}$ at RHIC. A model based on the recombination of thermal s-quarks describes the central $\phi$-meson $p_{T}$ spectrum as well as the baryon/meson ratio of $\Omega/\phi$ up to $p_{T}$ ~4 GeV/c.Comment: Submitted to J. Phys. G (Proceedings of the 9th International Conference on Strangeness in Quark Matter, Los Angeles, USA, March 26-31) 4 pages, 3 figure

Physics with Identified Particles at STAR

New physics results with identified particles at STAR are presented. Measurements at low $p_T$ address bulk properties of the collision, while those at high $p_T$ address jet energy loss in the bulk matter produced. Between these extremes, measurements at intermediate $p_T$ address the interplay between jets and the bulk. We highlight: measurements of $v_2$ fluctuations as a new, sensitive probe of the initial conditions and the equation of state; correlations involving multi-strange particles, along with ratios of identified particles to test coalescence as a mechanism of particle production at intermediate $p_T$; three particle azimuthal correlation to search for conical emission; and the energy and particle-type dependence of hadron production at high $p_T$ to study quark and gluon jet energy loss.Comment: 9 pages, 7 figures. To appear in the proceedings of the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2006), Shanghai, China, November 14-20, 200

First Results from Photon Multiplicity Detector at RHIC

We present the first measurement of multiplicity and pseudorapidity distributions of photons in the pseudorapidity region 2.3 < eta < 3.7 for different centralities in Au + Au collisions at sqrt{s_NN} = 62.4 GeV. The pseudorapidity distribution of photons, dominated by neutral pion decays, has been compared to those of identified charged pions, photons, and inclusive charged particles from heavy ion and nucleon-nucleon collisions at various energies. Scaling of photon yield with number of participating nucleons and limiting fragmentation scenario for inclusive photon production has been studied.Comment: Talk given at 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma (February 8 - 12, 2005); 4 pages and 6 figure

Jet-like correlations between Forward- and Mid- rapidity in p+p, d+Au and Au+Au collisions from STAR at 200 GeV

In this proceedings we present STAR measurements of two particle azimuthal correlations between trigger particles at mid-rapidity ($|\eta|<$ 1) and associated particles at forward rapidities (2.7 $<|\eta|<$ 3.9) in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. Two particle azimuthal correlations between a mid-rapidity trigger particle and forward-rapidity associated particles preferably probe large-x quarks scattered off small-x gluons in RHIC collisions. Comparison of the separate d- and Au-side measurements in d+Au collisions may potentially probe gluon saturation and the presence of Color Glass Condensate. In Au+Au collisions quark energy loss can be probed at large rapidities, which may be different from gluon energy loss measured at mid-rapidity.Comment: Quark Matter 06 Conference proceedings, submitted to Journal of Phys.

Event Structure at RHIC from p-p to Au-Au

Several correlation analysis techniques are applied to p-p and Au-Au collisions at RHIC. Strong large-momentum-scale correlations are observed which can be related to local charge and momentum conservation during hadronization and to minijet (minimum-bias parton fragment) correlations.Comment: 6 pages, 6 figures, 20th Winter Workshop on Nuclear Dynamics, Trelawny Beach, Jamaica, March 15-20, 200

Proton - Lambda correlations in Au-Au Collisions at sNN=200\sqrt{s_{NN}} = 200 GeV from the STAR experiment

The space-time evolution of the source of particles formed in the collision of nuclei can be studied through particle correlations. The STAR experiment is dedicated to study ultra-relativistic heavy ions collisions and allows to measure non-identical strange particle correlations. The source size can be extracted by studying $p-\Lambda$, $\bar{p}-\bar{\Lambda}$, $\bar{p}-\Lambda$ and $p-\bar{\Lambda}$ correlation functions. Strong interaction potential has been studied for these systems using an analytical model. Final State Interaction (FSI) parameters have been determined and has shown a significant annihilation process present in $\bar{p}-\Lambda$ and $p-\bar{\Lambda}$ systems not present in $p-\Lambda$ and $\bar{p}-\bar{\Lambda}$.Comment: contribution to the 20th Winter Workshop on Nuclear Dynamic

Centrality Dependence of Azimuthal Anisotropy of Strange Hadrons in 200 GeV Au+Au Collisions

Measurements of azimuthal anisotropy for strange and multi-strange hadrons are presented for the first time in their centrality dependence. The high statistics results of v2(pT) allow for a more detailed comparison to hydrodynamical model calculations. Number-of-constituent-quark scaling was tested for different centrality classes separately. Higher order anisotropies like v4(pT) are measured for multi-strange hadrons. While we observe agreement between measured data and models a deeper understanding and refinement of the models seem to be necessary in order to fully understand the details of the data.Comment: 4 pages, 2 figures; Strange Quark Matter 2006 conference proceedings, to appear in J. Phys.

Upsilon cross section in p+p collisions at STAR

The main focus of the heavy flavor program at RHIC is to investigate the properties of the dense matter produced in heavy-ion collisions by studying its effect on open heavy flavor and quarkonia production. This in turn requires a detailed understanding of their production in elementary p+p collisions so that the dense matter effects can be later unfolded. In this paper, we present the first mid-rapidity cross section measurement of bottomonium at $\sqrt{s}=200$ GeV with the STAR experiment. We compare our results with perturbative QCD calculations. A brief status on the study of charmonium in STAR is given.Comment: 4 pages, 4 figures. To appear in the proceedings of Quark Matter 2006 as a special issue of Journal of Physics G: Nuclear and Particle Physic

The first measurement of BB meson semi-leptonic decay contribution to non-photonic electrons at RHIC

We present the first measurement for the $B$ meson semi-leptonic decay contribution to non-photonic electrons at RHIC using non-photonic electron azimuthal correlations with charged hadrons in p+p collisions at $\sqrt{s_{NN}} = 200$ GeV from STAR.Comment: 4 pages, 3 figures, Quark Matter 2006 Proceedings, to appear in J. Phys.