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Title: Elliptic flow analysis in Au+Au collisions at {radical}(s{sub NN})=200 GeV: Fluctuations vs non-flow effects

Abstract

The cumulant method is applied to study elliptic flow (v{sub 2}) in Au+Au collisions at {radical}(s)=200A GeV, with the UrQMD model. In this approach, the true event plane is known and both the nonflow effects and event-by-event spatial ({epsilon}) and v{sub 2} fluctuations exist. Qualitatively, the hierarchy of v{sub 2}s from two-, four-, and six-particle cumulants is consistent with the STAR data; however, the magnitude of v{sub 2} in the UrQMD model is only 60% of the data. We find that the four- and six-particle cumulants are good measures of the real elliptic flow over a wide range of centralities except for the most central and very peripheral events. There the cumulant method is affected by the v{sub 2} fluctuations. In midcentral collisions, the four- and six-particle cumulants are shown to give a good estimation of the true differential v{sub 2}, especially at large transverse momentum, where the two-particle cumulant method is heavily affected by the nonflow effects.

Authors:
 [1];  [2];  [3];  [4];  [1];  [2]
  1. Frankfurt Institute for Advanced Studies (FIAS), Max-von-Laue-Strasse 1, D-60438 Frankfurt (Germany)
  2. (Germany)
  3. (China)
  4. Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt (Germany)
Publication Date:
OSTI Identifier:
20771140
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 72; Journal Issue: 6; Other Information: DOI: 10.1103/PhysRevC.72.064911; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; FLUCTUATIONS; GEV RANGE; GOLD 197 REACTIONS; GOLD 197 TARGET; HYDRODYNAMIC MODEL; MULTIPARTICLE SPECTROMETERS; PARTICLE IDENTIFICATION; TRANSVERSE MOMENTUM

Citation Formats

Zhu Xianglei, Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt, Physics Department, Tsinghua University, Beijing 100084, Bleicher, Marcus, Stoecker, Horst, and Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt. Elliptic flow analysis in Au+Au collisions at {radical}(s{sub NN})=200 GeV: Fluctuations vs non-flow effects. United States: N. p., 2005. Web. doi:10.1103/PhysRevC.72.064911.
Zhu Xianglei, Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt, Physics Department, Tsinghua University, Beijing 100084, Bleicher, Marcus, Stoecker, Horst, & Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt. Elliptic flow analysis in Au+Au collisions at {radical}(s{sub NN})=200 GeV: Fluctuations vs non-flow effects. United States. doi:10.1103/PhysRevC.72.064911.
Zhu Xianglei, Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt, Physics Department, Tsinghua University, Beijing 100084, Bleicher, Marcus, Stoecker, Horst, and Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt. Thu . "Elliptic flow analysis in Au+Au collisions at {radical}(s{sub NN})=200 GeV: Fluctuations vs non-flow effects". United States. doi:10.1103/PhysRevC.72.064911.
@article{osti_20771140,
title = {Elliptic flow analysis in Au+Au collisions at {radical}(s{sub NN})=200 GeV: Fluctuations vs non-flow effects},
author = {Zhu Xianglei and Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt and Physics Department, Tsinghua University, Beijing 100084 and Bleicher, Marcus and Stoecker, Horst and Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Max-von-Laue-Strasse 1, D-60438 Frankfurt},
abstractNote = {The cumulant method is applied to study elliptic flow (v{sub 2}) in Au+Au collisions at {radical}(s)=200A GeV, with the UrQMD model. In this approach, the true event plane is known and both the nonflow effects and event-by-event spatial ({epsilon}) and v{sub 2} fluctuations exist. Qualitatively, the hierarchy of v{sub 2}s from two-, four-, and six-particle cumulants is consistent with the STAR data; however, the magnitude of v{sub 2} in the UrQMD model is only 60% of the data. We find that the four- and six-particle cumulants are good measures of the real elliptic flow over a wide range of centralities except for the most central and very peripheral events. There the cumulant method is affected by the v{sub 2} fluctuations. In midcentral collisions, the four- and six-particle cumulants are shown to give a good estimation of the true differential v{sub 2}, especially at large transverse momentum, where the two-particle cumulant method is heavily affected by the nonflow effects.},
doi = {10.1103/PhysRevC.72.064911},
journal = {Physical Review. C, Nuclear Physics},
number = 6,
volume = 72,
place = {United States},
year = {Thu Dec 15 00:00:00 EST 2005},
month = {Thu Dec 15 00:00:00 EST 2005}
}
  • This article presents results on event-by-event elliptic flow fluctuations in Au+Au collisions at sq root(s{sub NN})= 200 GeV, where the contribution from non-flow correlations has been subtracted. An analysis method is introduced to measure non-flow correlations, relying on the assumption that non-flow correlations are most prominent at short ranges (|{Delta}{eta}|<2). Assuming that non-flow correlations are of the order that is observed in p+p collisions for long-range correlations (|{Delta}{eta}|>2), relative elliptic flow fluctuations of approximately 30-40% are observed. These results are consistent with predictions based on spatial fluctuations of the participating nucleons in the initial nuclear overlap region. It is foundmore » that the long-range non-flow correlations in Au+Au collisions would have to be more than an order of magnitude strongercompared to the p+p data to lead to the observed azimuthal anisotropy fluctuations with no intrinsic elliptic flow fluctuations.« less
  • We present STAR results on the elliptic flow v{sub 2} of charged hadrons, strange and multistrange particles from {radical}s{sub NN} = 200 GeV Au+Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC). The detailed study of the centrality dependence of v{sub 2} over a broad transverse momentum range is presented. Comparisons of different analysis methods are made in order to estimate systematic uncertainties. To discuss the nonflow effect, we have performed the first analysis of v{sub 2} with the Lee-Yang zero method for KS{sup 0} and {Lambda}. In the relatively low p{sub T} region, p{sub T} {le} 2 GeV/c,more » a scaling with m{sub T}-m is observed for identified hadrons in each centrality bin studied. However, we do not observe v{sub 2}(p{sub T}) scaled by the participant eccentricity to be independent of centrality. At higher p{sub T},2 {le} p{sub T} {le} 6 GeV/c,v{sub 2} scales with quark number for all hadrons studied. For the multistrange hadron {Omega}, which does not suffer appreciable hadronic interactions, the values of v{sub 2} are consistent with both m{sub T}-m scaling at low p{sub T} and number-of-quark scaling at intermediate p{sub T}. As a function of collision centrality, an increase of p{sub T}-integrated v{sub 2} scaled by the participant eccentricity has been observed, indicating a stronger collective flow in more central Au+Au collisions.« less
  • This Rapid Communication describes the measurement of elliptic flow for charged particles in Au+Au collisions at {radical}(s{sub NN})=200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider. The measured azimuthal anisotropy is presented over a wide range of pseudorapidity for three broad collision centrality classes for the first time at this energy. Two distinct methods of extracting the flow signal were used to reduce systematic uncertainties. The elliptic flow falls sharply with increasing |{eta}| at 200 GeV for all the centralities studied, as observed for minimum-bias collisions at {radical}(s{sub NN})=130 GeV.
  • We report on the first measurement of elliptic flow {nu}{sub 2}(p{sub T}) of multistrange baryons {xi}{sup -}+{xi}{sup +} and {omega}{sup -}+{omega}{sup +} in heavy-ion collisions. In minimum-bias Au+Au collisions at {radical}(s{sub NN})=200 GeV, a significant amount of elliptic flow, comparable to other nonstrange baryons, is observed for multistrange baryons which are expected to be particularly sensitive to the dynamics of the partonic stage of heavy-ion collisions. The p{sub T} dependence of {nu}{sub 2} of the multistrange baryons confirms the number of constituent quark scaling previously observed for lighter hadrons. These results support the idea that a substantial fraction of themore » observed collective motion is developed at the early partonic stage in ultrarelativistic nuclear collisions at the Relativistic Heavy Ion Collider.« less
  • Differential elliptic flow (v{sub 2}) for {phi} mesons and (anti)deuterons (d)d is measured for Au+Au collisions at {radical}(s{sub NN})=200 GeV. The v{sub 2} for {phi} mesons follows the trend of lighter {pi}{sup {+-}} and K{sup {+-}} mesons, suggesting that ordinary hadrons interacting with standard hadronic cross sections are not the primary driver for elliptic flow development. The v{sub 2} values for (d)d suggest that elliptic flow is additive for composite particles. This further validation of the universal scaling of v{sub 2} per constituent quark for baryons and mesons suggests that partonic collectivity dominates the transverse expansion dynamics.