Measurement of the $t\bar{t}$ differential cross section at large top quark transverse momentum in $\sqrt{s}$=8 TeV $pp$ collisions using the ATLAS detector at the LHC

Abstract

The top quark is the heaviest particle in Standard Model. When it is produced with a large Lorentz boost, its decay products tend to overlap, making the standard reconstruction techniques inefficient; large R jet substructure analysis techniques allow to increase the detection efficiency for these events. Various differential cross section measurements of boosted t-tbar from pp collisions with sqrt(s)=8 TeV are presented: with respect to the mass, to the transverse momentum and the pseudorapidity of the t-tbar system. The results here have been obtained using a sample of 20 fb^-1, recorded by ATLAS during 2012. The events are selected with a cut-based approach in the single lepton plus jets decay channel, where the lepton can be either an electron or a muon. The final background-subtracted distributions are corrected for the distortion introduced by the detector and selection effects using unfolding methods. The measurements are dominated by the systematic uncertainties, and are in agreement with the Standard Model, even if it can be seen a general tendency of the theoretical predictions to overestimate the measured cross section for increasing transverse momentum and mass of the t-tbar system.