Bulletin of the American Physical Society
APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011; Anaheim, California
Session E10: Mini-symposium on Early-Time and Long-Range Correlations in Relativistic Heavy Ion Collisions II |
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Sponsoring Units: DNP Chair: Prof. Steffen Bass, Duke University Room: Garden 1 |
Saturday, April 30, 2011 3:30PM - 3:42PM |
E10.00001: Azimuthal correlations of charged hadrons in Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV Eric Appelt Azimuthal correlations of charged hadrons were measured in $\sqrt{s_{NN}}$ = 2.76 TeV Pb+Pb collisions by the CMS experiment. The distributions exhibit anisotropies that are correlated with the event-by-event orientation of the reaction plane. Several methods were employed to extract the strength of the signal: the event-plane, cumulant and Lee-Yang Zeros methods. These methods have different sensitivity to correlations that are not caused by the collective motion in the system (non-flow correlations due to jets, resonance decays, and quantum correlations). The second Fourier coefficient of the charged hadron azimuthal distributions was measured as a function of transverse momentum, pseudorapidity and centrality in a broad kinematic range: $0.3 < p_T < 12.0$ GeV/c, $|\eta| < 2.4$, and in 9 centrality classes. [Preview Abstract] |
Saturday, April 30, 2011 3:42PM - 3:54PM |
E10.00002: Higher Harmonic Jet Tomography as a Probe of Fluctuating Initial Condition Geometries in A+A Barbara Betz, Giorgio Torrieri, Miklos Gyulassy While 2nd Fourier harmonics of jet quenching has been thoroughly explored in the literature and shown to be sensitive to (1) the underlying jet path length dependence of energy loss and (2) the differences between the mean eccentricity predicted by Glauber and CGC models of initial conditions, the sensitivity of higher harmonics, $v_n(p_T, b)$, to differences between the fluctuation spectrum of geometries has remained relatively unexplored. We demonstrate that higher azimuthal jet harmonics ($n\ge 3$) of $R_AA(p_T,\phi)$ and $I_AA(p_T,\phi)$ are remarkably insensitive to the differences of geometrical density fluctuations comparing between Glauber and KLN/CGC models of the initial conditions. Therefore, the differential elliptic $v_2(p_T)$ vs. $v_2^{I_{AA}}(p_T)$ moment correlation between the 2nd moment of monojet $R_{AA}$ and dijet $I_{AA}$ nuclear modifications factors remains the most sensitive probe to differentiate between CGC and Glauber initial state sQGP geometries. [Preview Abstract] |
Saturday, April 30, 2011 3:54PM - 4:06PM |
E10.00003: Elliptic flow measurement in $\sqrt{s_{NN}}$ = 2.76 TeV Pb+Pb collisions with the Lee-Yang Zeros method Shengquan Tuo Event-by-event azimuthal correlations of charged hadrons produced in high energy heavy ion collisions are likely to contain crucial information on the hot and dense matter produced in the early stages of the collisions. Such correlations may be caused by the collective motion in the system (flow), or by jets, resonance decays, and quantum correlations (non-flow). The Lee-Yang Zeros method of extracting elliptic flow (the second Fourier coefficient of the charged hadron azimuthal distributions) can successfully remove most of the non-flow correlations. We present the CMS measurement of elliptic flow in $\sqrt{s_{NN}}$ = 2.76 TeV Pb+Pb collisions as a function of transverse momentum, pseudorapidity and centrality obtained with the Lee-Yang Zeros method. The effect of jets on the signal extraction is also studied. [Preview Abstract] |
Saturday, April 30, 2011 4:06PM - 4:18PM |
E10.00004: $K_S^0$ and $\Lambda$ elliptic flow from the Beam Energy Scan at RHIC Jie Zhao In 2010, the first phase of the RHIC Beam Energy Scan (BES) program was successfully completed, with data collected at $\sqrt{s_{NN}}$ = 39, 11.5 and 7.7 GeV. The main goal of the BES is the search for the critical point and phase boundary predicted by QCD. Collective flow reflects dynamical evolution in high-energy heavy ion collisions. In particular, the strange hadron elliptic flow is believed to reflect early collision dynamics [1]. In this talk we will present the elliptic flow results for $K_S^0$ and $\Lambda$ from the RHIC beam energy scan. \\[4pt] [1]. J. Adams, et al., (STAR Collaboration), Nucl. Phys. A757, 102 (2005). [Preview Abstract] |
Saturday, April 30, 2011 4:18PM - 4:30PM |
E10.00005: Viscous hydrodynamic radial and elliptic flow from RHIC to LHC Chun Shen, Ulrich Heinz Using viscous hydrodynamics with a state-of-the-art equation of state (s95p-PCE) we present an excellent fit for the spectra and elliptic flow of all charged hadrons as well as identified pions and protons from Au+Au collisions of all centralities measured at the Relativistic Heavy Ion Collider (RHIC). We use this global fit to RHIC data as the basis for an extrapolation to Large Hadron Collider (LHC) energies and predict the analogous observables for Pb+Pb collisions at $\sqrt{s}=$\,2.76 and 5.5\,$A$\,TeV, assuming the same constant specific shear viscosity $\eta/s$ and thermalization time at both collision energies. Comparison with recent ALICE measurements of the elliptic flow of charged hadrons shows that the model slightly over-predicts the data, which indicates a possible temperature dependence of $(\eta/s)(T)$. The predicted centrality and transverse momentum dependence of spectra and elliptic flow for identified hadrons will be tested by upcoming experimental results. This will further test the model and shed additional light on possible variations of the quark-gluon transport coefficients between RHIC and LHC energies. [Preview Abstract] |
Saturday, April 30, 2011 4:30PM - 4:42PM |
E10.00006: Initial eccentricity fluctuations and their relation to higher-order flow harmonics Roy Lacey Considerable effort is currently being devoted to the quantitative extraction of the specific shear viscosity $\eta/s$, from flow measurements made at the Relativistic Heavy Ion Collider (RHIC). The initial eccentricity of the collision zone, as welll as its associated fluctuations, have proven to be an essential ingredient for such extractions. Experimental measurements of the eccentricity have not been possible to date and theoretical eccentricity estimates give results which differ by as much as 25-30\% -- a difference which leads to an approximate factor of two uncertainty in the extracted $\eta/s$ value. I will discuss the possible utility of higher-order flow measurements ($v_n$) as a constraint for distinguishing between the primary models used for eccentricity estimates. Such a constraint could be important for a more precise determination of the specific shear viscosity. [Preview Abstract] |
Saturday, April 30, 2011 4:42PM - 4:54PM |
E10.00007: Possibility to disentangle anisotropic flow, flow fluctuation, and nonflow Li Yi, Aihong Tang, Fuqiang Wang We suggest the possibility to disentangle anisotropic flow, flow fluctuation, and nonflow using two-, four-, six-particle azimuthal moments assuming Gaussian fluctuations. We show that such disentanglement is possible when the flow fluctuation are large, comparable to the average flow magnitude. When fluctuations are small, the disentanglement becomes difficult. We verify our results with toy-model Monte Carlo simulation. We plan to use this method in real data analysis. [Preview Abstract] |
Saturday, April 30, 2011 4:54PM - 5:06PM |
E10.00008: The Power Spectrum and Viscosity in Heavy Ion Collisions Agnes Mocsy In this talk we discuss the analogy between data from heavy-ion collisions and the Cosmic Microwave Background. We identify $p_T$ correlations data as the heavy-ion analogy to the CMB and extract a power-spectrum from the heavy-ion data. We define the ratio of the final state power-spectrum to the initial coordinate-space eccentricity as the transfer-function. From the transfer-function we find that higher n terms are suppressed and we argue that the suppression provides information on length scales like the mean-free-path. We make a rough estimate of the mean-free-path and find that it is larger than estimates based on the centrality dependence of $v_2$. [Preview Abstract] |
Saturday, April 30, 2011 5:06PM - 5:18PM |
E10.00009: Probing the CP violation signal in the quark-gluon plasma at RHIC using the PHENIX detector Nuggehalli Ajitanand A recently developed method for the quantitative measurement of charge separation about the reaction plane is used to constrain the values of the Local CP Violation in the sQGP medium discovered at RHIC. This method uses a correlation function whose shape is concave when there is a net separation of positive and negative charges. Correlations not specifically associated with a charge separation, do not influence the shape or magnitude of the correlation function. Detailed simulations are used to demonstrate the effectiveness of the method for the quantitative measurement of charge separation. Such measurements are a pre-requisite to the investigation of topological charge effects in the QGP leading to local CP violation. Results are presented for the application of the method to the PHENIX data from 200 GeV Au+Au collisions at RHIC. [Preview Abstract] |
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