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

Study of Cronin effect and nuclear modification of strange particles in d-Au and Au-Au collisions at 200 GeV in PHENIX

Effects of strangeness on nuclear modification in d-Au and Au-Au collisions at 200 GeV are studied, in order to quantify the effects of quark content and mass. Measurements of ratios of the yields in central collisions to the yields in peripheral collisions are performed for lambda baryon and phi meson. Found results show little dependence of particle suppression or enhancement on mass and strange content, but rather prominent difference in nuclear modification between mesons and baryons.Comment: 4 pages, 4 figures, proceedings of the Seventeenth International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004

Hadron Production at Intermediate pTp_T at RHIC

Large proton and antiproton enhancement with respect to pions has been observed at intermediate transverse momentum $p_T \approx$ 2-5 GeV/$c$ in Au+Au collisions at RHIC. To investigate the possible source of this anomaly, the production of $\phi$ mesons and two particle angular correlations triggered by mid-$p_T$ baryons or mesons are studied. We also present the first measurement of proton and antiproton production at $\sqrt{s_{NN}} = 62.4$ GeV in Au+Au collisions, which aims to study the energy dependence of the observed baryon enhancement.Comment: 7 pages, 5 figures, proceedings of Hot Quarks 2004 workshop, Taos Valley, New Mexico, 18-24 Jul 2004,, to be published in J. Phys.

Fluctuation Results from PHENIX

The PHENIX Experiment at the Relativistic Heavy Ion Collider has made measurements of event-by-event fluctuations in the net charge, the mean transverse momentum, and the charged particle multiplicity as a function of collision energy, centrality, and transverse momentum in heavy ion collisions. The results of these measurements will be reviewed and discussed.Comment: Proceedings for the Workshop on Correlations and Fluctuations in Relativistic Nuclear Collisions, April 21-23, 2005; 10 pages, 17 figure

Traces of Thermalization at RHIC

I argue that measurements of Au+Au collisions at 20, 130 and 200 GeV of the centrality dependence of the mean p_t together with p_t and net-charge fluctuations reflect the approach to local thermal equilibrium.Comment: 4 pages, 4 eps figures, for proc. Quark Matter 2004, to be published in J. Phys.

Visible infrared spin-scan radiometer

The visible infrared spin-scal radiometer (VISSR) may be considered as a camera system capable of simultaneously providing both visible and infrared earth and cloud cover pictures every 20 minutes from the geostationary synchronous meteorological satellite (SMS). With a 0.9-kilometer resolution in the visible spectrum and a 9-kilometer resolution in the IR spectrum, the VISSR/SMS SYSTEM makes its possible to study atmospheric dynamics through 24-hour continuous observation of cloud altitudes, patterns, motion, and temperature distributions

PHENIX Measurement of High-pTp_T Hadron-hadron and Photon-hadron Azimuthal Correlations

High-$p_T$ hadron-hadron correlations have been measured with the PHENIX experiment in \Cu and \pp collisions at $\sqrt{s_{NN}}=200$ GeV. A comparison of the jet widths and yields between the two colliding systems allows us to study the medium effect on jets. We also present a first measurement of direct photon-hadron correlations in \Au and \pp collisions. We find that the near-side yields are consistent with zero in both systems. By comparing the jet yields on the away side, we observe a suggestion of the expected suppression of hadrons associated with photons in \Au collisions.Comment: 5 pages, proceeding for parallel talk on Quark Matter 200

Correlations of Electrons from Heavy Flavor Decay with Hadrons in Au+Au and p+p Collisions

Measurements of electrons from the decay of open-heavy flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled p+p collisions. These measurements indicate that charm and bottom quarks interact with the hot-dense matter produced in heavy-ion collisions much more than expected. Here we extend these studies to two-particle correlations where one particle is an electron from the decay of a heavy-flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interactions between heavy quarks and the matter, such as whether the modifcation of the away-side-jet shape seen in hadron-hadron correlations is present when the trigger particle is from heavy-meson decay and whether the overall level of away-side-jet suppression is consistent. We statistically subtract correlations of electrons arising from background sources from the inclusive electron-hadron correlations and obtain two-particle azimuthal correlations at $\sqrt{s_{NN}}$ =200 GeV between electrons from heavy-flavor decay with charged hadrons in p+p and also first results in Au+Au collisions. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to p+p collisions.Comment: talk given at Winter Workshop in Nuclear Dynamics 201

π/K/p\pi/K/p production and Cronin effect from p+p, d+Au and Au+Au collisions at sNN=200\sqrt{s_{NN}}= 200 GeV from the PHENIX experiment

We present results on identified particle production in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV at mid-rapidity measured by the PHENIX experiment. The centrality and flavor dependence of the Cronin effect in d+Au collisions is measured. The Cronin effect for the protons in d+Au is larger than that for the pions, but not large enough to account for the ``anomalous'' proton to pion ratio in central Au+Au collisions.Comment: 5 pages, 3 figures, contribution to the proceedings of the 17th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004

An assessment of J/Psi formation in the light of initial RHIC data

Predictions of J/Psi formation at RHIC via "off-diagonal" combinations of charm and anticharm quarks in a region of color deconfinement are confronted with initial data from the PHENIX collaboration. We find that the measured centrality behavior places significant constraints on the various parameters which control model calculations of J/Psi formation. Within present statistical and systematic uncertainties, one can map out a region of parameter space within which the contribution of formation in a deconfined phase is allowed. As these uncertainties decrease and new data from d-Au interactions becomes available, it is expected that definitive tests for the presence of this formation mechanism will be possible. We anticipate that the rapidity and transverse momentum spectra will prove decisive for a final determination.Comment: 6 pages, 5 figures, presented at SQM2003, March 12-17, 2003. To be published in J. Phys.