Measurement of Inclusive Isolated Prompt Photon Production in Proton-Proton Collisions at $\sqrt{s}=7$ TeV with the ATLAS Detector

Prompt photons at hadron colliders are useful probes of perturbative quantum chromodynamics (pQCD), and are also found in signatures of new physics. A precise measurement of prompt photon production is both a useful test of theoretical models as well as an important step towards understanding final states that contain energetic photons. This thesis presents a measurement of the inclusive isolated prompt photon production cross section in proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ = 7 TeV. The data are collected with the ATLAS detector at the Large Hadron Collider, and correspond to 35 pb$^{-1}$ of integrated luminosity. The measurement is made in four photon pseudorapidity ($\eta^\gamma$) regions: $0 \leq |\eta^{\gamma}| < 0.6; 0.6 \leq |\eta^{\gamma}| < 1.37; 1.52 \leq |\eta^{\gamma}| < 1.81 $; and $1.81 \leq |\eta^{\gamma}| < 2.37 $; and covers photon transverse energies ($E^\gamma_T$) in the range 15 GeV $\leq E^\gamma_T$ < 400 GeV. Photon candidates are reconstructed and identified through the use of the ATLAS calorimeter and tracking systems. The residual background, primarily from neutral meson decays, is estimated using in-situ techniques based on observed distributions of the total transverse energy in a narrow cone around the photon candidate. The measurements are compared to predictions from next-to-leading order pQCD calculations, with good agreement for photon transverse energies greater than 25 GeV.