Dynamical photon production and v2γ in the quark-gluon plasma

Experiments have measured an elliptic flow of direct photons comparable to the flow of charged particles. Employing an on-shell partonic cascade, we investigate the microscopic processes that might lead to this unexpected large flow of photons. Compton scattering and quark-antiquark annihilation are important photon production processes in the QGP, which we implement in the cascade and subsequently show the agreement of their spectra in thermal equilibrium with analytic results. In order to be comparable with state-of-the art photon production rates at leading order, we make progress towards bremsstrahlung diagrams by computing their differential and total cross sections. Running the cascade in heavy-ion collision setups for RHIC and LHC, we find a very small photonic elliptic flow from the quark-gluon plasma phase.