Higgs boson studies: associated production with a vector boson and decay into b-quarks using the ATLAS Run-2 dataset.

On the 4th July 2012, the Standard Model of Particle Physics received further validation with the discovery of the Higgs boson; ushering in a new age of Higgs physics. This thesis presents some of my contributions to the current research in this field as a member of the ATLAS experiment at CERN. It explains how the ATLAS experiment fits within the CERN accelerator complex and the structure of the ATLAS detector, leading to a description of some of the work that I did towards the upgrade of its hardware, and my studies on the reconstruction of tracks in the detector. The thesis goes on to present the results of two analyses I worked on: The $VH, H \to bb$ (read: VHbb) Resolved Analysis and the $VH, H \to bb$ Boosted Analysis. Specific attention will be drawn to my fit studies in the Resolved Analysis, and the new trigger strategy I designed for the Boosted Analysis. The analyses make use of 139$\,fb^{-1}$ of proton-proton collision data at the centre-of-mass energy of $\sqrt{s}$ = 13 TeV, collected by the ATLAS detector between 2015 and 2018, to observe the Higgs boson decay to b-quarks via associated Vector Boson production ($VH, H \to bb$), and go on to provide differential cross-section measurements in bins of the transverse momentum of the vector bosons.