Measurement of Wγ and Zγ production at sqrt(s) = 7 TeV with the ATLAS Detector

We present measurements of high energy photons produced in association with either a W or Z boson in pp collisions at s = 7 TeV. The analysis uses the full data sample (∼35 pb−1) collected by the ATLAS experiment in 2010. Events with W and Z bosons decaying into high-pT electrons and muons are required in addition to have an isolated photon with ET > 15 GeV located outside a cone of radius 0.7 in η - φ space centered on the lepton(s) from the boson decay. 1 A total of 95 (97) pp → eνγ+X (pp → μνγ+X) and 25 (23) pp → e+e−γ + X (pp → μ+μ−γ + X) event candidates are selected. The dominant background of pp → lνγ+X processes is estimated using data-driven techniques based on isolation energy in a narrow cone around the photon candidate. The measured production cross sections, together with the kinematic distributions of the leptons and photons in data signal candidate events, are found to agree with the O(ααs) Standard Model predictions.