skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at {radical}(s{sub NN})=200 GeV

Abstract

The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured electrons with 0.3<p{sub T}<9 GeV/c at midrapidity (vertical bar y vertical bar <0.35) from heavy-flavor (charm and bottom) decays in Au+Au collisions at {radical}(s{sub NN})=200 GeV. The nuclear modification factor R{sub AA} relative to p+p collisions shows a strong suppression in central Au+Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy v{sub 2} with respect to the reaction plane is observed for 0.5<p{sub T}<5 GeV/c indicating substantial heavy-flavor elliptic flow. Both R{sub AA} and v{sub 2} show a p{sub T} dependence different from those of neutral pions. A comparison to transport models which simultaneously describe R{sub AA}(p{sub T}) and v{sub 2}(p{sub T}) suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid.

Authors:
; ; ; ; ; ; ;  [1]; ; ; ; ; ; ;  [2]; ; ; ; ;  [3]
  1. University of Colorado, Boulder, Colorado 80309 (United States)
  2. Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)
  3. Columbia University, New York, New York 10027 (United States) and Nevis Laboratories, Irvington, New York 10533 (United States) (and others)
Publication Date:
OSTI Identifier:
20951270
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 17; Other Information: DOI: 10.1103/PhysRevLett.98.172301; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANISOTROPY; B QUARKS; BNL; BROOKHAVEN RHIC; C QUARKS; COLLIDING BEAMS; COMPARATIVE EVALUATIONS; ELECTRONS; ENERGY LOSSES; ENTROPY; FLAVOR MODEL; GEV RANGE 100-1000; GOLD 197 BEAMS; GOLD 197 REACTIONS; GOLD 197 TARGET; IDEAL FLOW; PARTICLE DECAY; PIONS NEUTRAL; T QUARKS; TRANSPORT THEORY

Citation Formats

Adare, A., Bickley, A. A., Ellinghaus, F., Kelly, S., Kinney, E., Nagle, J. L., Seele, J., Wysocki, M., Afanasiev, S., Isupov, A., Litvinenko, A., Malakhov, A., Peresedov, V., Rukoyatkin, P., Zolin, L., Aidala, C., Bjorndal, M. T., Chi, C. Y., Cole, B. A., and D'Enterria, D. Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at {radical}(s{sub NN})=200 GeV. United States: N. p., 2007. Web. doi:10.1103/PHYSREVLETT.98.172301.
Adare, A., Bickley, A. A., Ellinghaus, F., Kelly, S., Kinney, E., Nagle, J. L., Seele, J., Wysocki, M., Afanasiev, S., Isupov, A., Litvinenko, A., Malakhov, A., Peresedov, V., Rukoyatkin, P., Zolin, L., Aidala, C., Bjorndal, M. T., Chi, C. Y., Cole, B. A., & D'Enterria, D. Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at {radical}(s{sub NN})=200 GeV. United States. doi:10.1103/PHYSREVLETT.98.172301.
Adare, A., Bickley, A. A., Ellinghaus, F., Kelly, S., Kinney, E., Nagle, J. L., Seele, J., Wysocki, M., Afanasiev, S., Isupov, A., Litvinenko, A., Malakhov, A., Peresedov, V., Rukoyatkin, P., Zolin, L., Aidala, C., Bjorndal, M. T., Chi, C. Y., Cole, B. A., and D'Enterria, D. Fri . "Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at {radical}(s{sub NN})=200 GeV". United States. doi:10.1103/PHYSREVLETT.98.172301.
@article{osti_20951270,
title = {Energy Loss and Flow of Heavy Quarks in Au+Au Collisions at {radical}(s{sub NN})=200 GeV},
author = {Adare, A. and Bickley, A. A. and Ellinghaus, F. and Kelly, S. and Kinney, E. and Nagle, J. L. and Seele, J. and Wysocki, M. and Afanasiev, S. and Isupov, A. and Litvinenko, A. and Malakhov, A. and Peresedov, V. and Rukoyatkin, P. and Zolin, L. and Aidala, C. and Bjorndal, M. T. and Chi, C. Y. and Cole, B. A. and D'Enterria, D.},
abstractNote = {The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured electrons with 0.3<p{sub T}<9 GeV/c at midrapidity (vertical bar y vertical bar <0.35) from heavy-flavor (charm and bottom) decays in Au+Au collisions at {radical}(s{sub NN})=200 GeV. The nuclear modification factor R{sub AA} relative to p+p collisions shows a strong suppression in central Au+Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy v{sub 2} with respect to the reaction plane is observed for 0.5<p{sub T}<5 GeV/c indicating substantial heavy-flavor elliptic flow. Both R{sub AA} and v{sub 2} show a p{sub T} dependence different from those of neutral pions. A comparison to transport models which simultaneously describe R{sub AA}(p{sub T}) and v{sub 2}(p{sub T}) suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid.},
doi = {10.1103/PHYSREVLETT.98.172301},
journal = {Physical Review Letters},
number = 17,
volume = 98,
place = {United States},
year = {Fri Apr 27 00:00:00 EDT 2007},
month = {Fri Apr 27 00:00:00 EDT 2007}
}
  • The PHENIX experiment has measured midrapidity (vertical bar {eta} vertical bar <0.35) transverse momentum spectra (0.4<p{sub T}<5.0 GeV/c) of electrons as a function of centrality in Au+Au collisions at {radical}(s{sub NN})=200 GeV. Contributions from photon conversions and from light hadron decays, mainly Dalitz decays of {pi}{sup 0} and {eta} mesons, were removed. The resulting nonphotonic electron spectra are primarily due to the semileptonic decays of hadrons carrying heavy quarks. Nuclear modification factors were determined by comparison to nonphotonic electrons in p+p collisions. A significant suppression of electrons at high p{sub T} is observed in central Au+Au collisions, indicating substantial energymore » loss of heavy quarks.« less
  • The nuclear modification factor R{sub AA} for {pi}{sub 0} production in Au+Au collisions at {radical}(s)=200A GeV is calculated and studied at high transverse momenta p{sub T}. The soft thermalized nuclear medium is described within the framework of relativistic ideal three-dimensional hydrodynamics. The energy loss of partonic jets is evaluated in the context of gluon bremsstrahlung in the thermalized partonic matter. We provide a systematic analysis of the azimuthal asymmetry of {pi}{sub 0} suppression at high p{sub T} in central and noncentral collisions at mid and forward rapidity. The determination of R{sub AA} as a function of p{sub T} at differentmore » azimuthal angles and different rapidities makes for a stringent test of our theoretical understanding of jet energy loss over a variety of in-medium path lengths, temperatures, and initial partonic jet energies. This lays the groundwork for a tomography of the nuclear medium.« less
  • We calculate the centrality dependence of transverse momentum (p{sub t}) spectra for direct photons in Au+Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC) energy {radical}(s{sub NN})=200 GeV, based on a realistic data-constrained (3+1)-dimensional hydrodynamic description of the expanding hot and dense matter, a reasonable treatment of the propagation of partons and their energy loss in the fluid, and a systematic study of the main sources of direct photons. The resultant p{sub t} spectra agree with recent PHENIX data in a broad p{sub t} range. The competition among the different direct photon sources is investigated at various centralities. Partonmore » energy loss in the plasma is considered for photons from fragmentation and jet-photon conversion, which causes about 40% decrease in the total contribution. In the high p{sub t} region, the observed R{sub AA} of photons is centrality independent at the accuracy of 5% based on a realistic treatment of energy loss. We also link the different behavior of R{sub AA} for central and peripheral collisions, in the low p{sub t} region, to the fact that the plasma in central collisions is hotter than that in peripheral ones.« less
  • 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 centralitiesmore » 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.« less
  • A simple kinematic model based on superposition of p+p collisions, relativistic geometry, and final-state hadronic rescattering is used to calculate various hadronic observables in {radical}(s{sub NN})=200 GeV Au+Au collisions and {radical}(s{sub NN})=5.5 TeV Pb+Pb collisions. The model calculations are compared with experimental results from several {radical}(s{sub NN})=200 GeV Au+Au collision studies. If a short hadronization time is assumed in the model, this model describes the trends of the observables from these experiments surprisingly well considering the model's simplicity. This also gives more credibility to the model predictions presented for {radical}(s{sub NN})=5.5 TeV Pb+Pb collisions.