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Study of the helicity distributions of Z[gamma] production at the CMS experimentChakaberia, Irakli January 1900 (has links)
Doctor of Philosophy / Department of Physics / Tim Bolton / This thesis represents the first study of the helicity distributions of Z[gamma] di-boson production at hadron colliders. I use 5 fb⁻¹ of [radical]s = 7 TeV center of mass energy proton-proton collision data, collected by the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC), to look at the angular distribution of the Z[gamma] [right arrow] e⁺e⁻[gamma] / [mu]⁺ [mu]⁻ [gamma] process and measure the helicity amplitudes that govern it. This study provides sensitivity to the interference terms between different quantum states and through the interference terms to the possible new physics. The final state is comprised of leptons (muon-antimuon or electron-positron pairs) with transverse momentum over 20 GeV and a photon with transverse energy over 30 GeV. Helicty amplitudes are measured for the total angular momentum of the quark-antiquark system up to J[subscript]q[subscript bar]q = 2. Four-dimensional multivariate analysis of the 2011 CMS data shows no significant deviations from the standard model prediction for the measured amplitudes.
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Measurement of Z +γ Production and Search for Anomalous Triple Gauge Couplings in Proton-antiproton Collisions at √S = 1.96 TevDeng, Jianrong 19 March 2008 (has links)
We present a measurement of ppbar->Zγ + X -> e<sup>+</sup>e<sup>-</sup>γ + X production using proton-antiproton collision data collected at the Collider Detector at Fermilab at a center of mass energy of 1.96 TeV. Zγ production provides a direct test of the triple neutral gauge couplings. A measurement of Zγ production cross section and search for anomalous ZZγ and Zγγ couplings are presented.
The data presented are from 1.1 fb<sup>-1</sup> of ppbar integrated luminosity collected at the CDF Detector. Electrons from Z decays are selected with E<sub>t</sub> > 20 GeV. Photons (E<sub>t</sub> > 7 GeV) are required to be well-separated from the electrons. There are 390 eeγ candidate events found with 1.1 fb<sup>-1</sup> of data, compared to the SM prediction of 375.3 à ± 25.2 events. The Standard Model prediction for the cross section for ppbar-> e<sup>+</sup>e<sup>-</sup>γ + X
production at √s = 1.96 TeV is 4.5 à ± 0.4 pb. The measured cross section is 4.7 à ± 0.6 pb. The cross section and kinematic distributions of the eeγ events are in good agreement with theoretical predictions.
Limits on the ZZγ and Zγγ couplings are extracted using the photon E<sub>t</sub> distribution of eeγ events with M<sub>eeγ</sub> > 100 GeV/c<sup>2</sup>. These are the first limits measured using CDF Run II data. These limits provide important test of the interaction of the photon and the Z boson. / Dissertation
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