Cold Nuclear Matter Effects and Heavy Quark Production in PHENIX

The PHENIX experiment uses semileptonic decay channels to measure open and closed heavy flavor cross sections across the rapidity range $-2.2 < y < 2.4$. High luminosity data are now available for p+p, d+Au, Cu+Cu and Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV, and for Au+Au collisions at $\sqrt{s_{NN}}$= 62 GeV. We discuss recent d+Au results for open heavy flavor and $J/\psi$ production, and discuss their implications for the cold nuclear matter contributions to heavy flavor production in heavy ion collisions.Comment: 8 pages, 9 figures. Proceedings for talk at Hard Probes 201

Dilepton radiation measured in PHENIX probing the strongly interacting matter created at RHIC

PHENIX has measured $e^+e^-$ pairs from p+p and Au+Au collisions as function of mass and $p_T$. The data can be used to probe the properties of dense matter formed in Au+Au collision. The relation between electron pairs and virtual photons is discussed.Comment: 4 pages, 3 figures, To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Open Heavy Flavor Production in Heavy Ion Collisions

The interaction of heavy partons, charm and beauty, with the matter created in heavy ion collisions has been of great interest in recent years. Heavy partons were predicted to interact less strongly with the matter than light partons. In apparent contrast to these predictions, unexpectedly strong suppression of non-photonic electrons from heavy flavor decays has been seen. However, significant experimental uncertainties remain, both in the measurements themselves and in the separation of the contribution from charm and beauty, which have complicated the interpretation of these results. The current experimental situation is critically reviewed and prospects for making these measurements more easily interpretable discussed.Comment: 8 pages, 5 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee v2: typos correcte

Highlights from PHENIX II: Exploring the QCD medium

Much of the present experimental effort at RHIC is now directed towards understanding the properties of the hot and dense colored medium created in A+A collisions. Recent results from PHENIX on the dynamical evolution of the medium and its response to high momentum probes are presented, and their impact on our overall understanding of heavy-ion collisions is discussed.Comment: 8 pages, 6 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee. Revised versio

Direct Photon Measurements at PHENIX

PHENIX has measured direct photons in p+p and Au+Au collisions at sqrt{s_{NN}}=200 GeV. The p+p measurement is in good agreement with pQCD expectations. The nuclear modification factor in Au+Au is found to be consistent with unity for all centralities, and is compared to theoretical models. The data are found in agreement with models that take into account initial state modifications, as well as with those that account also for final state modifications.Comment: 2 pages, 2 figures, to appear in the proceedings of Hard Probes 201

High pTp_T Parton Energy Loss from Jet Pair Correlation Observables in the PHENIX Experiment

By tuning several experimental observables, such as momentum and reaction plane, the PHENIX experiment has performed a systematic study of high $p_T$ parton energy loss in hot nuclear matter, as well as jet induced medium modifications, such as the ridge and shoulder. Baseline d+Au measurements are also studied to provide the comparison as control of cold nuclear matter effect.Comment: 4 pages, 6 figures. To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee, with minor correctio

Jet-Medium Interactions with Identified Particles

Identified particles have long been of great interest at RHIC in large part because of the baryon/meson differences observed at intermediate $p_T$ and the implications for hadronization via quark coalescence. With recent high statistics data identified particles are also now central to understanding the details of the jet-medium interactions and energy loss and hadron formation at intermediate and high $p_T$. In particular, high $p_T$ identified particle spectra along with two-particle correlations triggered with direct photons, neutral pions or electrons from heavy flavor decay with hadrons can provide information about how medium modifications to jet fragmentation depend on parton type. I will review recent results with identified particles both in heavy ion systems and the reference measurements in p+p collisions.Comment: Proceedings for Quark Matter 2009, Knoxville T

Weakness or Strength in the Golden Years of RHIC and LHC?

Recent LHC data suggest that perturbative QCD provides a qualitatively consistent picture of jet quenching. Constrained to RHIC pi0 suppression, zero parameter WHDG energy loss predictions agree quantitatively with the charged hadron v2 and D meson RAA measured at LHC and qualitatively with the charged hadron RAA. On the other hand, RHIC-constrained LHC predictions from fully strongly-coupled AdS/CFT qualitatively oversuppress D mesons compared to data; light meson predictions are on less firm theoretical ground but also suggest oversuppression. More detailed data from heavy, especially B, mesons will continue to help clarify our picture of the physics of the quark-gluon plasma. Since the approach of pQCD predictions to LHC data occurs at momenta >~ 15 GeV/c, a robust consistency check between pQCD and both RHIC and LHC data requires RHIC jet measurements.Comment: 4 pages. 3 figures. Proceedings for Hard Probes 2012. Minor grammatical and reference changes from v

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