@article{8ae5bb81202a4544801d5db06c5bfa2b,
title = "Observation of direct-photon collective flow in Au+Au collisions at √SNN = 200 GeV",
abstract = "The second Fourier component v2 of the azimuthal anisotropy with respect to the reaction plane was measured for direct photons at midrapidity and transverse momentum (pT) of 1-13 GeV/c in Au+Au collisions at √SNN = 200 GeV. Previous measurements of this quantity for hadrons with pT < 6 GeV/c indicate that the medium behaves like a nearly perfect fluid, while for pT > 6 GeV/c a reduced anisotropy is interpreted in terms of a path-length dependence for parton energy loss. In this measurement with the PHENIX detector at the Relativistic Heavy Ion Collider we find that for pT > 4 GeV/c the anisotropy for direct photons is consistent with zero, as expected if the dominant source of direct photons is initial hard scattering. However, in the pT < 4 GeV/c region dominated by thermal photons, we find a substantial direct photon v2 comparable to that of hadrons, whereas model calculations for thermal photons in this kinematic region significantly underpredict the observed v2.",
author = "A. Adare and S. Afanasiev and C. Aidala and Ajitanand, {N. N.} and Y. Akiba and H. Al-Bataineh and J. Alexander and K. Aoki and Y. Aramaki and Atomssa, {E. T.} and R. Averbeck and Awes, {T. C.} and B. Azmoun and V. Babintsev and M. Bai and G. Baksay and L. Baksay and Barish, {K. N.} and B. Bassalleck and Basye, {A. T.} and S. Bathe and V. Baublis and C. Baumann and A. Bazilevsky and S. Belikov and R. Belmont and R. Bennett and A. Berdnikov and Y. Berdnikov and Bickley, {A. A.} and Bok, {J. S.} and K. Boyle and Brooks, {M. L.} and H. Buesching and V. Bumazhnov and G. Bunce and S. Butsyk and Camacho, {C. M.} and S. Campbell and Chen, {C. H.} and Chi, {C. Y.} and M. Chiu and Choi, {I. J.} and Choudhury, {R. K.} and P. Christiansen and T. Chujo and P. Chung and O. Chvala and V. Cianciolo and Z. Citron and Dubey, {Awadhesh Kumar} and Mihael Makek and Alexander Milov and Deepali Sharma and Itzhak Tserruya",
note = "Office of Nuclear Physics in the Office of Science of the Department of Energy; National Science Foundation; Abilene Christian University Research Council; Research Foundation of SUNY; Ministry of Education, Culture, Sports, Science, and Technology (Japan); Japan Society for the Promotion of Science (Japan); Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (Brazil); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (Brazil); Natural Science Foundation of China (P.R. China); Ministry of Education, Youth and Sports (Czech Republic); Centre National de la Recherche Scientifique, Commissariat a l'Energie Atomique (France); Institut National de Physique Nucleaire et de Physique des Particules (France); Bundesministerium fur Bildung und Forschung (Germany); Deutscher Akademischer Austausch Dienst (Germany); Alexander von Humboldt Stiftung (Germany); Hungarian National Science Fund, OTKA (Hungary); Department of Atomic Energy (India); Department of Science and Technology (India); Israel Science Foundation (Israel); National Research Foundation (Korea); WCU program of the Ministry Education Science and Technology (Korea); Ministry of Education and Science, Russian Academy of Sciences, Federal Agency of Atomic Energy (Russia); VR (Sweden); Wallenberg Foundation (Sweden); U.S. Civilian Research and Development Foundation for the Independent States of the Former Soviet Union; U.S.-Hungarian Fulbright Foundation for Educational Exchange; U.S.-Israel Binational Science FoundationWe thank the staff of the Collider-Accelerator and Physics Departments at Brookhaven National Laboratory and the staff of the other PHENIX participating institutions for their vital contributions. We acknowledge support from the Office of Nuclear Physics in the Office of Science of the Department of Energy, the National Science Foundation, Abilene Christian University Research Council, Research Foundation of SUNY, and Dean of the College of Arts and Sciences, Vanderbilt University (",
year = "2012",
month = sep,
day = "19",
doi = "10.1103/PhysRevLett.109.122302",
language = "American English",
volume = "109",
journal = "Physical Review Letters",
issn = "0031-9007",
publisher = "American Institute of Physics",
number = "12",
}