Direct photon production in d+A and A+A collisions at RHIC

Abstract

Direct photon production in minimum bias d+Cu and d+Au and central Cu+Cu and Au+Au collisions at center of mass energies $\sqrt{s}=62.4$ GeV and 200GeV at RHIC is systematically investigated. We study the jet quenching effect, the medium-induced photon bremsstrahlung and jet-photon conversion in the hot QGP. We account for known cold nuclear matter effects, such as the isospin effect, the Cronin effect, shadowing and cold nuclear matter energy loss. It is shown that at high $p_T$ the nuclear modification factor for direct photons $R_{AA}^{\gamma }(p_T)<1$ is dominated by cold nuclear matter effects and there is no evidence for large cross section amplification due to medium-induced photon bremsstrahlung and jet-photon conversion in the medium. Comparison of numerical simulations to experimental data also rules out large Cronin enhancement and incoherent photon emission in the QGP but the error bars in the current experimental data cannot provide further constraints on the magnitudes of other nuclear matter effects.

slightly improved version; 10 pages, 7 figures; typos corrected; definitions for several symbols added

References in corpus (7)

• Non-Abelian energy loss in cold nuclear matter
• Measurement of direct photon production in p + p collisions at sqrt(s) = 200 GeV
• Testing the theory of QGP-induced energy loss at RHIC and the LHC
• A systematic study of direct photon production in heavy ion collisions
• Direct photons from relativistic heavy-ion collisions
• Direct Photon Production in p+p and d+Au Collisions Measured with the PHENIX Experiment
• Direct photons ~basis for characterizing heavy ion collisions~

Cited by in corpus (2)

• Disentangling centrality bias and final-state effects in the production of high-$p_T$ ${\pi }^0$ using direct $\gamma$ in $d$$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV
• Measurement of the inclusive isolated-photon production cross section in pp and Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV