Étalonnage des jets et mesure de la section efficace de production de paires de quarks top dans le canal hadronique à $\sqrt{s} = 8$ TeV avec l'expérience ATLAS auprès du LHC

The work presented in this thesis lies within the scope of the measurement of the top quark pair production cross-section in the fully hadronic channel at a centre of mass energy of 8 TeV, using the ATLAS detector at the LHC. After introducing the theoretical context of the Standard Model and the physics of the top quark, a description of the ATLAS detector design and of the event reconstruction is given. The first analysis presented focuses on the electromagnetic calorimeter performances, by studying in details the influence of the high voltage variations on the energy scale and resolution, using $Z \rightarrow ee$ events selected from the 4.5 $\rm fb^{-1}$ of 7 TeV data collected in 2011. The second part of the thesis is dedicated to jet performance studies. After reviewing the jet calibration procedure, measurements of the energy scale and of the resolution realized using a direct balance technique on Z+jet events selected from the 20.3 $\rm fb^{-1}$ of 8 TeV data collected in 2012, are presented. The results of these performance studies are used in the last part of this thesis, which is dedicated to the $t\bar{t}$ cross-section measurement on the full 2012 dataset. The presented analysis uses an analytical $\chi^{2}$ method to reconstruct the $t\bar{t}$ final state and a so-called ``ABCD'' method to estimate the background contribution in the selected signal region. The cross-section is measured with a 19% uncertainty and is compatible with Standard Model expectations.