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Studies of hadronic decays of high transverse momentum W and Z bosons with the ATLAS detector at the LHC

Chislett, RT; (2014) Studies of hadronic decays of high transverse momentum W and Z bosons with the ATLAS detector at the LHC. Doctoral thesis , UCL (University College London). Green open access

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Abstract

This work is based on data recorded by the ATLAS experiment at the LHC in 2011 at a centre of mass energy of 7 TeV and in 2012 at 8 TeV. The work predominantly focusses on searches for hadronically decaying W and Z bosons in the high $p_{T}$ regime such that both the decay products are contained within a single jet. Firstly, a selection using jet shapes boosted back into the centre of mass frame of the jet is used to locate a W and Z boson peak above the large QCD background in 2011 data and from this a cross section is extracted. This peak is then used to study a variety of grooming techniques designed to reduce the effects of pileup and leave only the components of jet related to the hard scatter. The effect of these techniques on a sample already containing strongly signal-like jets is assessed in terms of terms of data-Monte Carlo agreement, signal to background ratio and pileup dependence. They are found to perform well to a level that will be useful in future measurements at the LHC. Secondly an analysis designed to search for heavy diboson resonances in the hadronic channel is described. This search is based on a optimised version of a splitting and filtering technique investigated in the W and Z boson analysis with some additional substructure cuts. The analysis is run on 2012 data and the preliminary results and limits are presented. An excess corresponding to about 3.4$\sigma$ local significance is observed and this peak is currently undergoing a series of cross checks. This thesis also contains some performance studies of the ATLAS forward jet trigger in 2011 in terms of efficiency plots and work done to investigate applying calibration to the jet triggers. The calibration was seen to improve the jet trigger and was subsequently used in 2012 running.

Type: Thesis (Doctoral)
Title: Studies of hadronic decays of high transverse momentum W and Z bosons with the ATLAS detector at the LHC
Open access status: An open access version is available from UCL Discovery
Language: English
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/1443476
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