David Richard Shope

These proceedings present the method and performance of primary vertex reconstruction at the ATLAS experiment during Runs 1 and 2 at the LHC. The studies presented focus on data taken during 2012 at a centre-of-mass energy of , and during 2015-2016 at . Some predictions toward future runs are also presented. The measurement of the position and size of the luminous region and its use as a constraint to improve the primary vertex resolution are discussed.

Prestack depth imaging—consisting of both velocity/depth model building and prestack depth migration (PSDM)—is increasingly becoming the rule rather than the exception when the goal is to more clearly reveal a subsurface complicated by structure or velocity.

This thesis describes measurements of the inclusive Higgs boson production cross-sections via gluon-gluon fusion (ggF) and vector-boson fusion (VBF) through the H->WW*->evmv decay mode, using proton-proton collision data collected at sqrt(s) = 13 TeV by the ATLAS detector with the full dataset corresponding to an integrated luminosity of 36.1 ifb recorded in the years 2015 and 2016. An overview of the theoretical concepts and experimental apparatuses as well as the data processing techniques used for these results are provided, followed by the general strategy and background estimation of the analysis. Particular detail is given for the estimation of backgrounds originating from misidentified leptons, which is one of the specific focuses of the author's work. Finally, the statistical treatment of the analysis is presented, where the product of the H->WW* branching ratio times the ggF and VBF cross-sections are measured to be 11.4 ^{+1.2}_{-1.1} (stat.) ^{+1.8}_{-1.7} (syst.) pb and 0.50 ^{+0.24}_{-0.22} (stat.) \pm 0.17(syst.) pb, respectively, with no significant deviation from the Standard Model prediction being observed.