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Fuqiang Wang

Publications and source records attributed to Fuqiang Wang.

At least 91 records · Page 5Linked to original sources
arXiv2013

Eccentricity is not the only source of elliptic flow fluctuations

Sources of event-by-event elliptic flow fluctuations in relativistic heavy-ion collisions are investigated in a multiphase transport model. Besides the well-known initial eccentricity fluctuations, several other sources of dynamical fluctuations are identified. One is fluctuations in initial parton configurations at a given eccentricity. Second is quantum fluctuations in parton interactions during system evolution. Third is fluctuations caused by hadronization and final-state hadronic scatterings. The magnitudes of these fluctuations are investigated relative to eccentricity fluctuations and average flow magnitude. The fluctuations from the latter two sources are found to be negative. The results may have important implications to the interpretation of elliptic flow data.

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arXiv2013

Possibility to disentangle anisotropic flow, flow fluctuation, and nonflow assuming Gaussian fluctuations

We suggest the possibility to disentangle anisotropic flow, flow fluctuation, and nonflow using two-, four-, and six-particle azimuthal moments assuming Gaussian fluctuations. We show that such disentanglement is possible when the flow fluctuations are large, comparable to the average flow magnitude. When fluctuations are small, the disentanglement becomes difficult. We verify our results with a toy-model Monte Carlo simulation.

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arXiv2012

Decomposition of flow and nonflow in relativistic heavy-ion collisions

We propose a method to separate Δη-dependent and Δη-independent azimuthal correlations using two- and four-particle cumulants between pseudo-rapidity (η) bins in symmetric heavy-ion collisions. The Δη-independent correlation may be dominated by harmonic flows, a global correlation to the common collision geometry. The Δη-dependent correlation can be identified as nonflow, particle correlations unrelated to the common geometry. Our method exploits the ηsymmetry of the average harmonic flows and is "data-driven." We use the AMPT and HIJING event generators to illustrate our method. We discuss the decomposed Δη-independent and Δη-dependent correlations regarding flow and nonflow in the models.

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arXiv2012

Event-plane decorrelation over pseudo-rapidity and its effect on azimuthal anisotropy measurement in relativistic heavy-ion collisions

Within A Multi-Phase Transport model, we investigate decorrelation of event planes over pseudorapidity and its effect on azimuthal anisotropy measurements in relativistic heavy-ion collisions. The decorrelation increases with increasing η gap between particles used to reconstruct the event planes. The third harmonic event planes are found even anticorrelated between forward and backward rapidities, the source of which may root in the opposite orientation of the collision geometry triangularities. The decorrelation may call into question the anisotropic flow measurements with pseudorapidity gap designed to reduce nonflow contributions, hence the hydrodynamic properties of the quark-gluon plasma extracted from those measurements.

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arXiv2012

Effects of nuclear absorption on the antiLambda/antiproton ratio in relativistic heavy ion collisions

An enhanced antiLambda/antiproton ratio in heavy-ion relative to p+p collisions has been proposed as one of the signatures for the Quark-Gluon Plasma (QGP) formation. A significantly large (antiLambda+antiSigma0+1.1*antiSigma-)/antiproton ratio of 3.5 has been observed in the mid-rapidity and low transverse momentum region in central Au+Au collisions at the nucleon-nucleon center-of-mass energy of 4.9 GeV at the Alternating Gradient Synchrotron (AGS). This is an order of magnitude larger than the values in peripheral Au+Au collisions and p+p collisions at the corresponding energy. By using the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) transport model, we demonstrate that the observed large ratio can be explained by strong absorption of antiprotons (~99.9%) and antiLambdas (~99%) in dense nuclear matter created in central collisions. We find within the model that the initial antiLambda/antiproton ratio, mainly from string fragmentation, does not depend on the collision centrality, and is consistent with that observed in p+p collisions. This suggests that the observed large (antiLambda+antiSigma0+1.1*antiSigma-)/antiproton ratio at the AGS does not necessarily imply the formation of the QGP. We further study the excitation function of the ratio in UrQMD, which may help in the search and study of the QGP.

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arXiv2012

Geometrical Effect on Conical Emission of Correlated Hadrons

Dihadron correlations at intermediate p_T revealed novel structures on the away side of high p_T trigger particles at RHIC. The away-side correlations in central Au+Au collisions are significantly broader than in pp and d+Au collisions and in restricted kinematic range, double-peaked away from Δϕ=π. Three-particle correlations indicate conical emission of the away-side correlated hadrons at angles independent of associated particle p_T, consistent with formation of Mach-cone shock waves. In this talk we further investigate the conical emission phenomenon exploiting dihadron correlations as a function of the trigger particle azimuth from the reaction plane. Such correlations are sensitive to the collision geometry. We study these geometrical effects and discuss how they might be used to further our understanding of the medium created in heavy-ion collisions.

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arXiv2012

High-pt triggered dihadron correlations with vn background subtraction by STAR

STAR measurements of dihadron correlations with high-pt trigger partcles in Au+Au collisions at 200 GeV are presented with subtraction of v2, v3, and v4 backgrounds. The vn azimuthal anisotropies were measured by the two-particle cumulant method with η gap to reduce nonflow. The dihadron correlations relative to the v2 as well as the v3 harmonic planes are also presented. Implications of the results are discussed.

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arXiv2010

Non-flow correlations in a cluster model

We derive analytical forms for nonflow contributions from cluster correlation to the measurement of two-particle elliptic flow (v2{2}). We estimate nonflow contribution from rho->pi+pi decays and find it is negative but not a major contributor to the nonflow effect in v2{2}. We also estimate nonflow contribution from the recent STAR measurement of two-particle angular correlations.

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arXiv2010

Effects of Cluster Particle Correlations on Local Parity Violation Observables

We investigate effects of cluster particle correlations on two- and three-particle azimuth correlator observables sensitive to local strong parity violation. We use two-particle angular correlation measurements as input and estimate the magnitudes of the effects with straightforward assumptions. We found that the measurements of the azimuth correlator observables by the STAR experiment can be entirely accounted for by cluster particle correlations together with a reasonable range of cluster anisotropy in non-peripheral collisions. Our result suggests that new physics, such as local strong parity violation, may not be required to explain the correlator data.

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arXiv2010

Identification of flow-background to subtract in jet-like azimuthal correlation

We derive an analytical form for flow-background to jet-like azimuthal correlation in a cluster approach. We argue that the elliptic flow parameter to use in jet-correlation background is that from two-particle method excluding non-flow correlation unrelated to the reaction plane, but including cross-terms between cluster correlation and cluster flow. We verify our result with Monte Carlo simulations. We discuss implications of our finding in the context of jet-like correlations from STAR and PHENIX.

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arXiv2009

Non-flow, and what flow to subtract in jet-correlation

We derive analytical forms for non-flow contributions from cluster correlation to two-particle elliptic flow (v2{2}) measure. We also derive an analytical form for jet-correlation flow-background with the same cluster approach. We argue that the elliptic flow v2 parameter to be used in jet-correlation background is that from two-particle method excluding non-flow correlations unrelated to the reaction plane, but including cross-terms between cluster correlation and cluster flow. We verify our result with Monte Carlo simulations. We discuss how one may obtain the v2 parameter for jet-correlation background experimentally.

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arXiv2009

Hard Probes are the "Meridian Line", sQGP is the Forbidden City

Relativistic heavy-ion collisions at BNL/RHIC have created a hot and dense nuclear matter, the strongly interacting Quark-Gluon Plasma (sQGP). Hard probes, high transverse momentum particles and jets, interact with the sQGP medium and lose energy. The interactions modify the properties of the hard probes; the medium responds to the energy loss of those probes in a collective way. Many properties of the sQGP have been learned from the modifications to the probes and the medium responses. I will review jet-like correlation results from RHIC, especially those measured by three-particle correlations, and discuss some of the fascinating physics.

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arXiv2009

Cumulant versus jet-like three-particle correlations

Two-particle jet-like azimuthal correlations have revealed intriguing modifications to the away-side of high pt trigger particles in relativistic heavy-ion collisions. Three-particle jet-like azimuthal correlation and three-particle azimuthal cumulant have been analyzed in experiments in attempt to distinguish conical emission of jet-correlated particles from other physics mechanisms. We investigate the difference between three-particle jet-like correlation and three-particle cumulant in azimuth. We show, under the circumstance where the away-side two-particle correlation is relatively flat in azimuth and similar in magnitude to the azimuthal average of the two-particle correlation signal, that the three-particle cumulant cannot distinguish conical emission from other physics mechanisms. The three-particle jet-like correlation, on the other hand, retains its discrimination power.

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arXiv2009

Spectra and radial flow at RHIC with Tsallis statistics in a Blast-Wave description

We have implemented the Tsallis statistics in a Blast-Wave model and applied it to mid-rapidity transverse-momentum spectra of identified particles measured at RHIC. This new Tsallis Blast-Wave function fits the RHIC data very well for $p_T<$3 GeV/$c$. We observed that the collective flow velocity starts from zero in p+p and peripheral Au+Au collisions growing to 0.470 $\pm$ 0.009($c$) in central Au+Au collisions. The $(q-1)$ parameter, which characterizes the degree of non-equilibrium in a system, changes from $0.100\pm0.003$ in p+p to $0.015\pm0.005$ in central Au+Au collisions, indicating an evolution from a highly non-equilibrated system in p+p collisions toward an almost thermalized system in central Au+Au collisions. The temperature and collective velocity are well described by a quadratic dependence on $(q-1)$. Two sets of parameters in our Tsallis Blast-Wave model are required to describe the meson and baryon groups separately in p+p collisions while one set of parameters appears to fit all spectra in central Au+Au collisions.

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arXiv2008

Analysis Method for Jet-Like Three-Particle Azimuthal Correlations

Jet-like three-particle azimuthal correlations can discriminate various physical scenarios that have been proposed to explain the observed strong modification to two-particle azimuthal correlations. The three-particle correlation analysis is notoriously difficult in heavy-ion collisions due to the large combinatoric backgrounds. We describe the general idea behind the jet-like three-particle azimuthal correlation analysis, with emphasis put on the subtraction of the combinatoric backgrounds. We discuss in detail the various systematic effects in such an analysis.

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arXiv2007

In-Medium Properties of Jets

Modifications of jet-like azimuthal correlations have revealed novel properties of the medium created in relativistic heavy-ion collisions. Experimental results on jet-like 2- and 3-particle correlations, specificly "punch-through" at high transverse momentum, broadening at low and modest transverse momentum, and particularly the possible experimental evidence for conical flow, are reviewed. Future prospects of jet-like correlations and their physics potential are discussed.

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