Measurement of Hadronic Event Shapes and Jet Substructure in Proton-Proton Collisions at 7.0 TEV Center-Of-Mass Energy with the Atlas Detector at The Large Hadron Collider

This thesis presents the first measurement of 6 hadronic event shapes in proton-proton collisions at a center-of-mass energy of √ s = 7 TeV using the ATLAS detector at the Large Hadron Collider. Results are presented at the particle-level, permitting comparisons to multiple Monte Carlo event generator tools. Numerous tools and techniques that enable detailed analysis of the hadronic final state at high luminosity are described. The approaches presented utilize the dual strengths of the ATLAS calorimeter and tracking systems to provide high resolution and robust measurements of the hadronic jets that constitute both a background and a signal throughout ATLAS physics analyses. The study of the hadronic final state is then extended to jet substructure, where the energy flow and topology within individual jets is studied at the detector level and techniques for estimating systematic uncertainties for such measurements are commissioned in the first data. These first substructure measurements in ATLAS include the jet mass and sub-jet multiplicity as well as those concerned with multi-body hadronic decays and color flow within jets. Finally, the first boosted hadronic object observed at the LHC – the decay of the top quark to a single jet – is presented.