A study of jet substructure in ttbar events with the ATLAS detector at the LHC

Being able to identify and accurately measure the properties of high mass ttbar events is critical to many physics studies at the LHC ranging from measurements of differential cross-sections at high transverse momenta to looking for signatures of new physics. In high mass events, the individual decay products of the top quark hadronic decay t->Wb; W->qq' can often merge into a single large-R (in the case of the anti-kt algorithm) jet containing the b-quark and decays of the W. These large-R jets can be deconstructed and by looking at their substructure, the original decay products can be identified. This allows the large-R jets to be identified as top quarks and their properties better measured. This thesis will use the full ATLAS Run-II dataset to study the different substructure variables in ttbar events to see which ones best identify the final state and are also well described by Physics simulation programmes. The analysis will lead to an ATLAS publication. The analysis will be carried out within the ATLAS collaboration and will make use of the Run-II dataset, which will have undergone reconstruction to identify and calibrate the physics objects required for the analysis. The analysis will make use of a local software framework for data analysis.