Early QCD Analyses with photons at CMS

The measurement of inclusive photon production is a crucial step for the understanding of Standard Model Physics at the Large Hadron Collider (LHC) and an important prerequisite for many new physics searches. The identification of photons' experimental signatures and their discrimination against instrumental background due to hadronic activity is a challenging task in the severe LHC environment. A robust set of selection criteria for the identification of isolated photons at the LHC start-up using the CMS detector was developed. In this work, the performance of such criteria is studied using proton-proton collision events at $\sqrt{s} = 7~$TeV corresponding to $74~$nb$^{-1}$. Results obtained in data are compared with expectations from Monte Carlo simulation and good agreement is observed.