Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session H13: Minisymposium on Correlations and Jets in Heavy-Ion Collisions |
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Sponsoring Units: DNP Chair: Jim Thomas, Lawrence Berkeley National Laboratory Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis F |
Sunday, April 13, 2008 8:30AM - 9:06AM |
H13.00001: Correlations and Jets in Heavy-Ion Collisions Invited Speaker: Interactions of jets with the medium produced in heavy-ion collisions can provide important insight into the properties of the medium. This can be explored via particle correlations. Two-particle correlations with high $p_{T}$ triggers have shown modified structures on both the near-side and away-side. The near-side shows a ``ridge'', a structure that is correlated in azimuth but exhibits a long range structure in pseudo-rapidity. The ridge could be explained by partons bent in chromo-magnetic fields, couplings with longitudinal flow, or other mechanisms. The away-side shows a broadened and even double peaked structure in azimuth. Conical emission from Mach-cone shock waves or \v{C}eronkov gluon radiation along with other physics mechanisms have been suggested to explain this modification. Three-particle correlations and correlations with identified particles have been employed to provide further insight into both the near-side and away-side modifications. This talk will review medium responses to jet probes studied with 2-particle and 3-particle correlations. [Preview Abstract] |
Sunday, April 13, 2008 9:06AM - 9:18AM |
H13.00002: Decomposition of awayside components of dijet correlation in Au+Au collisions at $\sqrt{S_{NN}}=200$ GeV at PHENIX Chin-Hao Chen At intermediate transverse momentum, dijet angular correlations show a local minimum at $\Delta\phi$, peaking one radian away from $\pi$. This structure indicates that the awayside jet is modified by the medium created in heavy ion collisions. We present the measurement of inclusive photon-hadron $\Delta\eta$ - $\Delta\phi$ correlations from $\sqrt{s_{NN}}=200$ GeV Au+Au collisions in PHENIX. In central collisions, an enhancement in per trigger associated hadrons in the near-side (trigger) jet is observed for $0.5<\Delta\eta<0.7$. The awayside components, as a function of $\Delta\eta$, are decomposed using $\delta\phi$ into a head region, corresponding to the ``punch through'' jet, and a shoulder region containing the medium response. The awayside components are found to be independent of $\Delta\eta$. $p_T$ weighted yields allow investigation of how the transverse momentum is distributed between near- and away-side associated particles. [Preview Abstract] |
Sunday, April 13, 2008 9:18AM - 9:30AM |
H13.00003: Jet study in doubly triggered $h^\pm$-$h^\pm$ correlations in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV Eric Vazquez A hot dense medium exceeding the critical energy density for the formation of a partonic state of matter is created in Au+Au collisions at RHIC. This dense matter is extremely opaque to high energy partons and therefore leads to strong modifications of di-jets traversing the medium. These modifications are typically studied by comparing the di-hadron azimuthal correlation functions in Au+Au collisions to those in p+p collisions. However, a surface bias occurs in events triggered on a single hadron due to the larger probability of a high-$p_T$ parton emerging with little or no energy loss from production points near the surface of the medium. This effect can be minimized, and in fact controlled, by studying events in which the production of two high-$p_T$ hadrons at large azimuthal separation is required. We present preliminary results of such an analysis performed in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. [Preview Abstract] |
Sunday, April 13, 2008 9:30AM - 9:42AM |
H13.00004: Study of Baryon to Meson Ratios of Associated Hadrons in Di-Hadron Correlation Maria Cristina Suarez We present results on baryon and meson ($\bar{p}$, $p$ and $\pi^{\pm}$) spectra and ratios of associated hadrons in the di-hadron correlations with a high-$p_{T}$ hadron trigger. We will discuss the differences between the inclusive (non-triggered) ratios and the observed ratios in ``jet'' and ``ridge'' parts of 2-dimensional di-hadron $\Delta \phi$ - $\Delta \eta$ correlations from 200 GeV central Au+Au collisions. We will discuss these results in conjunction with our measurements from d+Au collisions, also we will compare the ratios to those from inclusive $pp$ and $e^{+}$$e^{-}$ data and various models. [Preview Abstract] |
Sunday, April 13, 2008 9:42AM - 9:54AM |
H13.00005: Direct measurement of fragmentation photons in p+p collisions at $\sqrt{s} = 200$~GeV with the PHENIX experiment Ali Hanks In heavy ion collisions direct photons are an important observable because they are penetrating, and therefore remain largely insensitive to the final state effects that lead to jet quenching. Perturbative QCD calculations predict a contribution to the direct photon yield of up to $30\%$ from photons produced through fragmentation. In heavy ion collisions it is expected that this contribution is modified due to additional stimulated photon bremsstrahlung as well as energy loss of the partons through gluon radiation prior to fragmentation. A measure of such photons would provide direct observation of the energy loss of jets in the medium. Thus measurements of the fragmentation component to direct photon yields in both p+p and Au+Au collisions provides an important test of pQCD predictions and of the nuclear modification factor. Photons produced through jet fragmentation can be measured by selecting photons associated with jets using hadron-photon correlations, providing a natural way of extracting properties of the jet. However, this signal is small compared to the contributions to the inclusive yield from photons produced through $\pi^{0}$ , $\eta$, and other mesonic decays, requiring a precise determination of these backgrounds. We present results from the application of this approach to PHENIX p+p data and discuss its potential for signal extraction in heavy ion collisions. [Preview Abstract] |
Sunday, April 13, 2008 9:54AM - 10:06AM |
H13.00006: Photon-hadron Correlations Measured in Au-Au Collisions at $\sqrt{s_{NN}}=200$ GeV with the PHENIX Detector Megan Connors Two particle correlations are used to understand the jet tomography of heavy ion collisions at RHIC. In particular, photon-hadron correlations are an excellent probe of medium affects. Using the photon momentum to tag the momentum of the opposing jet, we can study jet energy loss and measure the modified fragmentation function. This talk will present the photon-hadron correlations in Au-Au collisions measured from data collected during Run7 by the PHENIX experiment. To make this correlation, we employ an established statistical procedure to extract the direct photon yield which subtracts the background from decay photons from our inclusive measurement. Previous measurements are improved by the increase in statistics achieved in Run 7. [Preview Abstract] |
Sunday, April 13, 2008 10:06AM - 10:18AM |
H13.00007: Measurement of High $p_T$ Flow and Jet Correlation in Au+Au Measurement of High $p_T$ Flow and Jet Correlation in Au+Au Collisions at $\sqrt{S_{NN}}=200GeV$ from PHENIX Rui Wei Single hadron yields at high transverse momentum $p_T$ are observed to be strongly suppressed in central Au+Au collisions. This suppression is thought to be the result of jet quenching, and the observed high $p_T$ hadrons are thought to be dominated by fragmentation of hard scattered partons emitted from the surface of the overlap region. Although extremely simplistic, this picture would lead to a small but finite $v_2$ and a relatively unmodified near-side jet shape for these high $p_T$ hadrons. A combined study of the $v_2$ and near-side jet correlations of leading hadrons can improve our understanding of the particle production mechanism and geometrical bias in this $p_T$ region. PHENIX experiment installed a new reaction-plane detector and collected 5.5 billion Au+Au events in RUN7. The significantly improved ability to determine the reaction-plane and large statistics allow a more detailed study of flow and jet correlation. Results on the elliptic flow and jet correlation for high $p_T$ hadrons are presented. [Preview Abstract] |
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