Measurement of the inclusive isolated prompt photon cross section in $pp$ collisions at $\sqrt{s}= 7~TeV$ with the ATLAS detector using 4.9 $fb^{-1}$

A measurement of the cross section for the inclusive production of isolated prompt photons in $pp$ collisions at a center-of-mass energy $\sqrt{s} = 7~TeV$ is presented. The measurement covers the pseudorapidity ranges $|\eta^\gamma|<1.37$ and $1.52\leq|\eta^\gamma|<2.37$, in the transverse energy range $100\leq \eta^{\gamma}<1000~GeV$. The results are based on an integrated luminosity of 4.9~$fb^{-1}$, collected with the ATLAS detector at the LHC. Photon candidates are identified by exploiting the fine granularity of the electromagnetic calorimeter, which provides event-by-event rejection of the dominant background from photons produced by $\pi^0$ decays, and of the inner detector, which allows the reconstruction of photons that convert to electron-positron pairs. Residual background in the selected sample is estimated using data-driven techniques based on the observed distribution of the isolation energy in a narrow cone around the photon candidate. The results are compared with next-to-leading order perturbative QCD calculations.