PHENIX Direct Photons in 200 GeV p+p and Au+Au Collisions

Abstract

We present the first positive direct photon results in Au+Au at sqrt{s_NN} = 200 GeV along with initial p+p results at the same energy. The p+p result is found to be consistent with NLO perturbative QCD predictions within its large uncertainties. In central Au+Au collisions, an excess over expected background as large as 200-300% is observed from p_T = 4-12 GeV/c. This large signal is shown to be consistent with the scaled pQCD photon prediction, together with suppression of meson background sources.

4 pages, 5 figures, contribution to the proceedings of the 17th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter, Oakland, January 11-17, 2004). To appear in the proceedings (Journal of Physics G)

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• High pT leading hadron suppression in nuclear collisions at sqrt(s_NN) = 20 -- 200 GeV: data versus parton energy loss models
• Relevance of baseline hard proton-proton spectra for high-energy nucleus-nucleus physics
• The Vector Probe in Heavy-Ion Reactions
• Jets in Nuclear Collisions: Status and Perspective
• PHENIX Highlights
• Theory Highlights of Quark Matter 2004
• Direct-Photon Production from SPS to RHIC Energies
• In-medium effects on electromagnetic probes
• Direct Photon Measurement at RHIC-PHENIX
• Direct Photons at RHIC
• Can the QGP be found using only an Electromagnetic Calorimeter?