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Article
Measurement of Direct Photons in Au plus Au Collisions at root s(NN)=200 GeV
Physical Review Letters
Document Type
Article
Disciplines
Publication Version
Published Version
Publication Date
10-9-2012
DOI
10.1103/PhysRevLett.109.152302
Abstract
We report the measurement of direct photons at midrapidity in Au + Au collisions at root s(NN) = 200 GeV. The direct photon signal was extracted for the transverse momentum range of 4 GeV/c < pT < 22 GeV/c, using a statistical method to subtract decay photons from the inclusive photon sample. The direct photon nuclear modification factor R-AA was calculated as a function of p(T) for different Au + Au collision centralities using the measured p + p direct photon spectrum and compared to theoretical predictions. R-AA was found to be consistent with unity for all centralities over the entire measured pT range. Theoretical models that account for modifications of initial direct photon production due to modified parton distribution functions in Au and the different isospin composition of the nuclei predict a modest change of R-AA from unity. They are consistent with the data. Models with compensating effects of the quark-gluon plasma on high-energy photons, such as suppression of jet-fragmentation photons and induced-photon bremsstrahlung from partons traversing the medium, are also consistent with this measurement.
Copyright Owner
American Physical Society
Copyright Date
2012
Language
en
File Format
application/pdf
Citation Information
S. Afanasiev, Sergey Belikov, Paul Constantin, Nathan Conrad Grau, et al.. "Measurement of Direct Photons in Au plus Au Collisions at root s(NN)=200 GeV" Physical Review Letters Vol. 109 Iss. 15 (2012) p. 152302 Available at: http://works.bepress.com/craig-ogilvie/82/
This is an article from Physical Review Letters 109 (2012): 152302-1, doi:10.1103/PhysRevLett.109.152302. Posted with permission.