期刊
PHYSICAL REVIEW C
卷 81, 期 3, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevC.81.034911
关键词
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资金
- 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
- Dean of the College of Arts and Sciences, Vanderbilt University (USA)
- Ministry of Education, Culture, Sports, Science, and Technology
- Japan Society for the Promotion of Science (Japan)
- Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (Brazil)
- Natural Science Foundation of China
- Ministry of Education, Youth and Sports (Czech Republic)
- Centre National de la Recherche Scientifique
- Commissariat a l'Energie Atomique, and Institut National de Physique Nucleaire et de Physique des Particules (France)
- Ministry of Industry, Science and Tekhnologies, Bundesministerium fur Bildung und Forschung, Deutscher Akademischer Austausch Dienst, and Alexander von Humboldt Stiftung (Germany)
- Hungarian National Science Fund, OTKA (Hungary)
- Department of Atomic Energy (India)
- Israel Science Foundation (Israel)
- National Research Foundation (Korea)
- Ministry of Education and Science, Russia Academy of Sciences, Federal Agency of Atomic Energy (Russia)
- VR and the Wallenberg Foundation (Sweden)
- US Civilian Research and Development Foundation for the Independent States of the Former Soviet Union
- US-Hungarian NSF-OTKA-MTA
- U.S.-Israel Binational Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Physics [GRANTS:14024153] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Physics [0855569] Funding Source: National Science Foundation
PHENIX has measured the e(+)e(-) pair continuum in root s(NN) = 200 GeV Au+Au and p+p collisions over a wide range of mass and transverse momenta. The e(+)e(-) yield is compared to the expectations from hadronic sources, based on PHENIX measurements. In the intermediate-mass region, between the masses of the phi and the J/psi meson, the yield is consistent with expectations from correlated c (c) over bar production, although other mechanisms are not ruled out. In the low-mass region, below the phi, the p+p inclusive mass spectrum is well described by known contributions from light meson decays. In contrast, the Au+Au minimum bias inclusive mass spectrum in this region shows an enhancement by a factor of 4.7 +/- 0.4(stat) +/- 1.5(syst) +/- 0.9(model). At low mass (m(ee) < 0.3 GeV/c(2)) and high p(T) (1 < p(T) < 5 GeV/c) an enhanced e(+)e(-) pair yield is observed that is consistent with production of virtual direct photons. This excess is used to infer the yield of real direct photons. In central Au+Au collisions, the excess of the direct photon yield over the p+p is exponential in p(T), with inverse slope T = 221 +/- 19(stat) +/- 19(syst) MeV. Hydrodynamical models with initial temperatures ranging from T-init similar or equal to 300-600 MeV at times of 0.6-0.15 fm/c after the collision are in qualitative agreement with the direct photon data in Au+Au. For low p(T) < 1 GeV/c the low-mass region shows a further significant enhancement that increases with centrality and has an inverse slope of T similar or equal to 100 MeV. Theoretical models underpredict the low-mass, low-p(T) enhancement.
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