Mainz 2014 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 112: Top-Quarks: Assoziierte Produktion
T 112.1: Vortrag
Donnerstag, 27. März 2014, 16:45–17:00, P102
Measurement of the top-quark pair + photon production cross section in the muon + jets channel in pp collisions at 8 TeV — Till Arndt1, Markus Backes1, Günter Flügge1, Heiko Geenen1, Felix Höhle1, Yvonne Küssel1, Claudia Pistone1, Oliver Pooth1, Achim Stahl1, and •Heiner Tholen2 — 1III Phys. Inst. B, RWTH Aachen University — 2Universität Hamburg
The production cross section of top-quark pairs associated with a photon is measured in pp-collisions at a centre-of-mass energy of at 8 TeV, with the CMS detector at LHC, using data corresponding to an integrated luminosity of Lint = 19.7 fb−1. The measurement is performed in the muon + jets decay channel. The signal region is defined by the final state of the process pp → W+W−b b γ, with a transverse energy of the photon of ET(γ)>20 GeV and a distance between the photon and the b-quark in η−φ space, Δ R(γ, b/b) > 0.1. The normalized cross-section is measured to be R = σt t + γ / σt t = (1.07 ± 0.07 (stat.) ± 0.27 (.syst))· 10−2. Using a CMS cross section measurement of inclusive t t production at 8 TeV, σt tCMS = 227 ± 15 pb, the top-quark pair + photon production cross section is σt t + γCMS =2.4 ±0.2 (stat.) ±0.6 (syst.) pb. The result agrees with the standard model expectation of σt t + γSM = 1.8± 0.5 pb.