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Detailed measurement of the e(+)e(-) pair continuum in p plus p and Au plus Au collisions at root s(NN)=200 GeV and implications for direct photon production
Physical Review C
  • Andrew Adare, University of Colorado, Boulder
  • Sergey Belikov, Iowa State University
  • Paul Constantin, Iowa State University
  • Nathan C. Grau, Iowa State University
  • John C. Hill, Iowa State University
  • John G. Lajoie, Iowa State University
  • Alexandre Lebedev, Iowa State University
  • Craig Ogilvie, Iowa State University
  • H. Pei, Iowa State University
  • Jan Rak, Iowa State University
  • Marzia Rosati, Iowa State University
  • S. Skutnik, Iowa State University
  • Carla Vale, Iowa State University
  • et al.
  • PHENIX Collaboration, PHENIX Collaboration
Document Type
Article
Disciplines
Publication Version
Published Version
Publication Date
3-1-2010
DOI
10.1103/PhysRevC.81.034911
Abstract
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.
Comments

This article is published as Adare, Ad, S. Afanasiev, C. Aidala, N. N. Ajitanand, Y. Akiba, H. Al-Bataineh, J. Alexander et al. "Detailed measurement of the e+ e− pair continuum in p+ p and Au+ Au collisions at s NN= 200 GeV and implications for direct photon production." Physical Review C 81, no. 3 (2010): 034911. DOI:10.1103/PhysRevC.81.034911. Posted with permission.

Copyright Owner
American Physical Society
Language
en
File Format
application/pdf
Citation Information
Andrew Adare, Sergey Belikov, Paul Constantin, Nathan C. Grau, et al.. "Detailed measurement of the e(+)e(-) pair continuum in p plus p and Au plus Au collisions at root s(NN)=200 GeV and implications for direct photon production" Physical Review C Vol. 81 Iss. 3 (2010) p. 034911
Available at: http://works.bepress.com/craig-ogilvie/247/