Wednesday 18 November
09:00 - 13:00
The Large Hadron Collider (LHC) is the largest and most powerful accelerator in the world.
Proton bunches rotating in opposite directions are accelerated to 6.5 TeV inside the LHC ring
and collided at four different points around the ring with an energy of 13 TeV. The ATLAS
detector is a general purpose particle physics detector built around one of the collision points
and is used to study the products of the high energy proton-proton collisions.
The identification of jets containing b hadrons (b-jets) is an important part of many physics
analyses, including those presented in this thesis. The calibration of the b-jet identification
algorithms is performed with data. The first part of this thesis describes the method to
calibrate the probability of a light-flavour or gluon jet to be mistakenly identified as a b-jet.
The second part presents a search for new phenomena in events with top quark pairs and large
missing transverse energy using the full LHC Run 2 dataset. No evidence for physics beyond
the Standard Model is found and the analysis is instead used to exclude various extensions of
the Standard Model. The third part of the thesis describes an effective field theory approach to
Higgs boson pair production.