Measurement of Inclusive Isolated Prompt Photon Production at √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 √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 (η) regions: 0 < |ηγ| < 0.6; 0.6 < |ηγ| < 1.37; 1.52 <|ηγ|< 1.81; and 1.81 <|ηγ|< 2.37; and covers photon transverse energies (ET) in the range 15 GeV < ET < 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.