Regular Article – Experimental Physics
Direct photons measured by the PHENIX experiment at RHIC
University of California, 900 University Avenue, Riverside, CA, 92521, USA
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Published online: 9 December 2006
Results from the PHENIX experiment at RHIC on direct photon production in p+p, d+Au, and Au+Au collisions at =200 GeV are presented. In p+p collisions, direct photon production at high pT behaves as expected from perturbative QCD calculations. The p+p measurement serves as a baseline for direct photon production in Au+Au collisions. In d+Au collisions, no effects of cold nuclear matter are found within the large uncertainty of the measurement. In Au+Au collisions, the production of high pT direct photons scales as expected for particle production in hard scatterings. This supports jet quenching models, which attribute the suppression of high pT hadrons to the energy loss of fast partons in the medium produced in the collision. Low pT direct photons, measured via e+e- pairs with small invariant mass, are possibly related to the production of thermal direct photons.
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