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Measurement of Direct Photons in Au plus Au Collisions at root s(NN)=200 GeV

Afanasiev, S.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Al-Jamel, A.; Alexander, J.; Aoki, K.; Aphecetche, L.; Armendariz, R. and Aronson, S. H., et al. (2012) In Physical Review Letters 109(15).
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... (More)
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. (Less)
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Physical Review Letters
volume
109
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15
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American Physical Society
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  • scopus:84867370476
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1079-7114
DOI
10.1103/PhysRevLett.109.152302
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English
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2012-12-12 09:14:42
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@article{1ebbead6-7795-4663-8796-c8a7df616868,
  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 &lt; pT &lt; 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.},
  articleno    = {152302},
  author       = {Afanasiev, S. and Aidala, C. and Ajitanand, N. N. and Akiba, Y. and Al-Jamel, A. and Alexander, J. and Aoki, K. and Aphecetche, L. and Armendariz, R. and Aronson, S. H. and Averbeck, R. and Awes, T. C. and Azmoun, B. and Babintsev, V. and Baldisseri, A. and Barish, K. N. and Barnes, P. D. and Bassalleck, B. and Bathe, S. and Batsouli, S. and Baublis, V. and Bauer, F. and Bazilevsky, A. and Belikov, S. and Bennett, R. and Berdnikov, Y. and Bjorndal, M. T. and Boissevain, J. G. and Borel, H. and Boyle, K. and Brooks, M. L. and Brown, D. S. and Bucher, D. and Buesching, H. and Bumazhnov, V. and Bunce, G. and Burward-Hoy, J. M. and Butsyk, S. and Campbell, S. and Chai, J. -S. and Chernichenko, S. and Chi, C. Y. and Chiba, J. and Chiu, M. and Choi, I. J. and Chujo, T. and Cianciolo, V. and Cleven, C. R. and Cobigo, Y. and Cole, B. A. and Comets, M. 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R. and Younus, I. and Yushmanov, I. E. and Zajc, W. A. and Zaudtke, O. and Zhang, C. and Zimanyi, J. and Zolin, L.},
  issn         = {1079-7114},
  language     = {eng},
  number       = {15},
  publisher    = {American Physical Society},
  series       = {Physical Review Letters},
  title        = {Measurement of Direct Photons in Au plus Au Collisions at root s(NN)=200 GeV},
  url          = {http://dx.doi.org/10.1103/PhysRevLett.109.152302},
  volume       = {109},
  year         = {2012},
}