Direct Photon Elliptic Flow at BNL Relativistic Heavy Ion Collider   (RHIC) and CERN Large Hadron Collider (LHC)
  We use an event-by-event hydrodynamical description of the heavy-ion collision process with Glauber initial conditions to calculate the thermal emission of photons. The photon rates in the hadronic phase follow from a spectral function approach and a density expansion, while in the partonic phase they follow from the AMY perturbative rates. The calculated photon elliptic flows are lower than those reported recently by both the ALICE and PHENIX collaborations. 
Young-Min Kim, Chang-Hwan Lee, Derek Teaney and Ismail Zahed
nucl-th hep-ph nucl-ex