UC Berkeley

This dissertation presents the first measurement of the top quark pair differential cross-section as a function of the hadronic top candidate transverse momentum that uses boosted top quark identification techniques. This allows to extend the measurement into the TeV range, with the cross-section reported for top candidate transverse momentum between 300 GeV and 1.2 TeV. The measurement is performed using events reconstructed in the lepton+jets channel in 20.3 fb$^{-1}$ of $\sqrt{s}$ = 8 TeV proton-proton collision data collected by the ATLAS experiment. Previous measurements have reported the cross-section as a function of the top quark kinematics. To allow for a robust top candidate definition, independent of assumptions required to isolate the kinematics of individual partons, the cross-section presented here is reported at the stable particle level. The cross-section is reported within a fiducial region closely following the detector-level event selection to minimize uncertainties associated with extrapolations beyond the detector acceptance. To illustrate the evolution of the uncertainties associated with extrapolating the particle level results to the usual top parton definition, the results are also presented within the full phase-space at the parton level.