Study Of Hadronic Event Shape Variables In Multijet Final States In Pp Collisions At Sqrt S

Study of Hadronic Event-shape Variables in Multijet Final States in Pp Collisions at $\sqrt{s}$

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 7.0 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.

Study of Double Parton Scattering in Photon + 3 Jets Final State

This book mainly focuses on the study of photon + 3 jets final state in Proton-Proton Collisions at √s = 7TeV, searching for patterns of two (or more) distinct hard scatterings in the same collision, i.e the so-called Double Parton Scattering (DPS). A new method by using Monte Carlo generators was performed and provides higher order corrections to the description of the Single Parton Scattering (SPS) background. Further it is investigated whether additional contributions from DPS can improve the agreement between the measured data and the Monte Carlo predictions. The current theoretical uncertainties related to the SPS background are found to be larger than expectation. At the same time a rich set of DPS-sensitive measurements is reported for possible further interpretation.