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New physics searches in the ZZ sector with the ATLAS experiment 10.17863/CAM.16566 Barber, Thomas This thesis investigates the prospects of measuring anomalous triple gauge boson couplings in the ATLAS detector at the Large Hadron Collider (LHC). The most general (V ZZ, V = Z, g) vertex is parametrised by four couplings, fV = Z,g i=4,5 , all of which are zero in the Standard Model. Non-zero couplings would manifest themselves as an excess of events in ZZ diboson channels, and, if observed, would be a direct probe of new physics beyond the Standard Model. A set of criteria are outlined to select events recorded by ATLAS in two such channels, ZZ to llll(l = e, mu) and ZZ to llnunu. With 1 fb-1 of integrated luminosity at a centre of mass energy of sqrt(s) = 7 TeV, ATLAS can expect to observe 10+/-1 events in the ZZ to llll channel, with 0.5+0.9-0.2 background events. In the ZZ to llnunu channel, 6.2+/-0.7 signal events are expected, with a background of 1.9+2.0-0.2 events. The expected sensitivity of ATLAS to non-zero anomalous couplings is calculated by performing extended, unbinned maximum-likelihood fits to the Z boson transverse momentum spectrum. For 1 fb-1 of integrated luminosity at sqrt(s) = 7 TeV, ATLAS has the potential to place constraints on the coupling parameters of |fZi | < 0.06 and |fig | < 0.07 at the 95% confidence level. These limits assume a form factor with a cutoff of Lambda_FF = 1.2 TeV. As a prelude to ZZ observation, criteria are defined to select Z to ll(l = e, mu) events in the first 315 nb-1 of ATLAS pp collision data at sqrt(s) = 7 TeV. In total 57 events are observed in the electron channel, with 109 in the muon channel, leading to cross section measurements of sigma(Z to ee) = 0.70+/-0.09 (stat)+/-0.10 (syst)+/-0.08 (lumi) pb and sigma(Z to mumu) = 0.90+/-0.09 (stat) +/-0.07 (syst) +/-0.10 (lumi) pb, both of which are consistent with the Standard Model predictions. In addition, this thesis presents a summary of developments made to the Data Acquisition (DAQ) system of the ATLAS Semiconductor Tracker (SCT). These include the construction of a test system, involving a scaled-down version of the entire SCT readout chain. The test system was subsequently used to develop a number of new DAQ features, including a hardware-based event simulator and monitoring framework. University of Cambridge 2011-03-15 Thesis Doctoral Doctor of Philosophy (PhD) eng This work was made possible by the Science and Technology Research Council (STFC) under STFC student number PPA/S/S/2006/04325. http://www.dspace.cam.ac.uk/handle/1810/236979 https://www.repository.cam.ac.uk/handle/1810/236979 https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/7592e33f-8236-4432-9061-08f4ce9b2fe1/download c3d5595117dffac43b7cfb0bbc155979 https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/0abac607-9397-4e44-9585-e36afb0599a1/download 0b1a12d4eb169023d6d65183e2d7aac9 https://www.rioxx.net/licenses/all-rights-reserved/ ATLAS Anomalous couplings LHC Electroweak Diboson