Date of Award

Summer 8-12-2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Physics & Astronomy

First Advisor

H. H. Williams

Abstract

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 ≤ η < 0.6; 0.6 ≤ η < 1.37; 1.52 ≤ η < 1.81; and 1.81 ≤ η < 2.37; and covers photon transverse energies (ET) in the range 15 GeV ≤ ET < 400 GeV. Photon candidates are reconstructed and identif ied 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.

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