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Measurement of vector boson pair production using hadronic decays of high transverse momentum W and Z bosons at the ATLAS detector

Freeborn, DPW; (2016) Measurement of vector boson pair production using hadronic decays of high transverse momentum W and Z bosons at the ATLAS detector. Doctoral thesis , UCL (University College London). Green open access

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Abstract

This thesis describes an analysis measuring the WW+WZ production cross-section and setting limits on anomalous triple gauge couplings, in the semileptonic final state, using 20.28 fb^-1 data from the ATLAS detector at a centre of mass energy of √s = 8 TeV. Two different topologies are studied: one with two distinct jets arising from the hadronic vector boson decay, and one with the hadronic decay products merged into a single large-radius jet at high transverse momentum. In the resolved channel, the signal cross-section is measured with 4.45 σ significance with respect to the background-only hypothesis and yielding a cross-section in the fiducial phase space of 219 pb, in agreement with the Standard Model prediction. In the boosted channel, the cross-section in the fiducial phase space was measured to be 7.6 +/- 4.9 pb, lower than the expected standard model cross section of 15.3 pb, with a significance of 2.05 σ. Limits are set on anomalous contributions to triple gauge interaction vertices. For the resolved analysis, the observed 95% CL limits are -6.0 < c_WWW/Λ^2 < 6.0 =, -39 < c_W/Λ^2 < 46 and -6.9 < c_B/Λ^2 < 12.1 TeV^-2. For the boosted analysis, the equivalent observed limits are -2.54 < c_WWW/Λ^2 < 2.52, -15.6 < c_W/Λ^2 < 17.2 and -3.65 < c_B/Λ^2 < 4.94 TeV ^-2. The thesis also presents a performance study of the ATLAS jet triggers, during the period of upgrade from Run 1 to Run 2. The study assesses a proposed technique to improve the performance of the HLT jet trigger algorithms, by combining selected regions of interest into a larger combined region.

Type: Thesis (Doctoral)
Title: Measurement of vector boson pair production using hadronic decays of high transverse momentum W and Z bosons at the ATLAS detector
Event: University College London
Open access status: An open access version is available from UCL Discovery
Language: English
Keywords: Particle physics, gauge bosons, bosons, ATLAS, hadronic, semileptonic, Parton distribution functions, Electroweak, jets, boosted jets, jet substructure, triple gauge couplings, aTGCs
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/1508242
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