Jet Correlations with Identified Particles from PHENIX: Methods and Results

Azimuthal angle two particle correlations have been shown to be a powerful probe for extracting novel features of the interaction between hard scattered partons and the medium produced in Au+Au collisions at RHIC. At intermediate $p_T$, 2-5GeV/c, the jets have been shown to be significantly modified in both their particle composition and their angular distribution compared to p+p collisions. Additionally, angular two particle correlations with identified hadrons provide information on the possible role of modified hadronization scenarios such as partonic recombination, which might allow medium modified jet fragmentation by connecting hard scattered partons to low $p_T$ thermal partons. PHENIX has excellent particle identification capabilities and has developed robust techniques for extracting jet correlations from the large underlying event. We present recent PHENIX results from Au+Au collisions for a variety of $p_T$ and particle type combinations. We also present p+p measurements as a baseline. We show evidence that protons and anti-protons in the $p_T$ region of enhanced baryon and anti-baryon single particle production are produced in close angle pairs of opposite charge and that the strong modifications to the away side shape observed for charged hadron correlations are also present when baryons are correlated.Comment: talk given at XIth International Workshop on Correlations and Fluctuations in Multiparticle Production, Hangzhou China November 21-24 200

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

STAR Measurements of Bottom to Charm Ratio and Heavy Quark Interaction with the QCD Medium through Non-Photonic Electron-Hadron Correlations

We present STAR measurements of relative charm and bottom contributions to NPE from $p+p$ collisions at $\sqrt{s}$= 200 and 500 GeV energies. We report the total bottom quark production cross section from p+p collisions at $\sqrt{s}= 200$ GeV extracted from NPE spectrum and B to D ratios. We also present the NPE-hadron azimuthal correlations from $Au+Au$ collisions at \sqrtsNN = 200 GeV from the 2010 RHIC run where we have collected high statistics data set with low photonic conversion background.Comment: 4 pages, 3 figures. Proceedings for XXII International Conference on Ultra-relativistic Nucleus-Nucleus Collision (Quark Matter 2011), 22 - 28 May 2011, Annecy, Franc

Heavy Quarkonia Production in p+p Collisions from the PHENIX Experiment

Quarkonia provide a sensitive probe of the properties of the hot dense medium created in high energy heavy ion collisions. Hard scattering processes result in the production of heavy quark pairs that interact with the collision medium during hadronization. These in-medium interactions convey information about the fundamental properties of the medium itself and can be used to examine the modification of the QCD confining potential in the collision environment. Baseline measurements from p+p and d+Au collision systems are used to distinguish cold nuclear matter effects while measurements from heavy ion collision systems are used to quantify in-medium effects. The PHENIX experiment has the capability of detecting heavy quarkonia at $1.2<|\eta|<2.2$ via the $\mu^+\mu^-$ decay channel and at $|\eta|<0.35$ via the $e^+e^-$ decay channel. Recent runs have resulted in the collection of high statistics p+p data sets that provide an essential baseline reference for heavy ion measurements and allow for further critical evaluation of heavy quarkonia production mechanisms. The latest PHENIX results for the production of the $J/\psi$ in p+p collisions are presented and future prospects for $\psi'$, $\chi_{c}$ and $\Upsilon$ measurements are discussed.Comment: 4 pages, 2 figures, Proceedings for Quark Matter 200

Initial temperature and EoS of quark matter from direct photons

The time evolution of the quark gluon plasma created in gold-gold collisions of the Relativistic Heavy Ion Collider (RHIC) can be described by hydrodynamical models. Distribution of hadrons reflects the freeze-out state of the matter. To investigate the time evolution one needs to analyze penetrating probes, such as direct photon spectra. Distributions of low energy photons was published in 2010 by PHENIX. In this paper we analyze a 3+1 dimensional solution of relativistic hydrodynamics and calculate momentum distribution of direct photons. Using earlier fits of this model to hadronic spectra, we compare photon calculations to measurements and find that the initial temperature of the center of the fireball is at least 519+-12 MeV, while for the equation of state we get c_s= 0.36+-0.02.Comment: Talk at the VI Workshop on Particle Correlations and Femtoscopy, Kiev, September 14-18, 2010. 6 pages, 1 figure. This work was supported by the OTKA grant NK73143 and M. Csanad's Bolyai scholarshi

Recent PHENIX Results on Open Heavy Flavor

Throughout the history of the RHIC physics program, questions concerning the dynamics of heavy quarks have generated much experimental and theoretical investigation. A major focus of the PHENIX experiment is the measurement of these quarks through their semi-leptonic decay channels at mid and forward rapidity. Heavy quark measurements in $p+p$ collisions give information on the production of heavy flavor, without complications from medium effects. New measurements in $d+$Au and Cu+Cu indicate surprising cold nuclear matter effects on these quarks at midrapidity, and provide a new baseline for interpretation of the observed suppression in Au+Au collisions. When considered all together, these measurements present a detailed study of nuclear matter across a wide range of system size and temperature. Here we present preliminary PHENIX measurements of non-photonic electron spectra and their centrality dependence in $d$+Au and Cu+Cu, and discuss their implications on the current understanding of parton energy loss in the nuclear medium.Comment: 4 pages, 3 figures, to appear in the proceedings of Quark Matter 201

Quarkonium production in ultra-relativistic nuclear collisions: suppression vs. enhancement

After a brief review of the various scenarios for quarkonium production in ultra-relativistic nucleus-nucleus collisions we focus on the ingredients and assumptions underlying the statistical hadronization model. We then confront model predictions for J/$\psi$ phase space distributions with the most recent data from the RHIC accelerator. Analysis of the rapidity dependence of the J/$\psi$ nuclear modification factor yields first evidence for the production of J/$\psi$ mesons at the phase boundary. We conclude with predictions for charmonium production at the LHC.Comment: 8 pages, 6 figures, invited paper, Quark Matter 2006 conference, Shanghai, submitted to J. Phys.

Collective Flow Measurements from the PHENIX Experiment

Recent collective flow measurements including higher moment event anisotropy from the PHENIX experiment are presented, and the particle type, beam energy dependence and the relation with jet modification are discussed. The measured higher order event anisotropy with event plane defined at forward rapidities and the long range correlation with large $\eta$ gaps are both consistent with initial geometrical fluctuation of the participating nuclei. In 200 GeV Au+Au collisions, higher order event anisotropy, especially simultaneous description of v$_2$ and v$_3$, is found to give an additional constraining power on initial geometrical condition and viscosity in the hydrodynamic calculations. v$_2$, v$_3$ and v$_4$ are almost unchanged down to the lower colliding energy at 39 GeV in Au+Au. The measured two particle correlation with subtraction of the measured v$_n$ parameters shows a significant effect on the shape and yield in the associate particle $\Delta\phi$ distribution with respect to the azimuthal direction of trigger particles. However some medium responses from jet suppression or jet modification seems to be observed. Direct photon v$_2$ has been measured in 200 GeV Au+Au collisions. The measured v$_2$ is found to be small at high p$_{\rm T}$ as expected from non-suppressed direct photon R$_{\rm AA}$ $\simeq$ 1, which can be understood as being dominated by prompt photons from initial hard scattering. On the other hand, at lower p$_{\rm T}$ $<$ 4 GeV/c it is found to be significantly larger than zero, which is comparable to other hadron v$_2$, where thermal photons are observed.Comment: 8 pages, 10 figures, Quark Matter 2011 proceeding

Evidence for charmonium generation at the phase boundary in ultra-relativistic nuclear collisions

We investigate the transition from suppression to enhancement of J/psi mesons produced in ultra-relativistic nuclear collisions in the framework of the statistical hadronization model. The calculations are confronted with the most recent data from the RHIC accelerator. This comparison yields first direct evidence for generation of J/psi mesons at the phase boundary. Based on the success of this approach we make specific predictions for LHC energy.Comment: 5 pages, 2 figures; final version accepted for publication in Phys. Lett. B (Fig.1 containd a new set of calculations