Direct photons in ATLAS@LHC

The ATLAS detector at the LHC is capable of efficiently separating photons and neutral hadrons based on their shower shapes over a wide range in η, ϕ and E _T , either in addition to or instead of isolation cuts. This provides ATLAS with a unique strength for direct photon and γ-jet physics (“tomography”) as well as access to the unique capability to measure non-isolated photons from fragmentation or from the medium. We present a first look at the ATLAS direct photon measurement capabilities in p+p and Pb+Pb collisions at LHC energies over the region |η| < 2.4.