Search for the Standard Model $H\to\gamma\gamma$ decays with the ATLAS detector at the LHC

A light Standard Model Higgs boson, with mass between 114 and $approx$150 GeV, is favored by precise measurements of electroweak radiative corrections and other theory predictions. One of the most important channels to search for this particle in this mass region is the decay $H ightarrowgammagamma$. We investigate the ATLAS discovery potential for a light Higgs boson in the two photon decay mode. In addition to the inclusive analysis we consider also the reconstruction of diphoton systems produced in association with jets or missing $E_T$. The studies are based on a realistic detector simulation of Monte Carlo signal and background events.