Measurement of the Top Quark Pair Production Cross Section in the Electron and Jets Channel at $\sqrt{s}$ = 7 TeV with the CMS Detector at the LHC

The top quark is the heaviest fundamental particle observed in nature. The high mass leads to its decay before a hadronisation takes place which allows the measurement of its properties from the decay products. Measurements of the properties of the top quark allow for precision tests of the Standard Model of particle physics. Furthermore, top quark production is a dominant background in many searches for physics beyond the Standard Model. The Large Hadron Collider (LHC) is a high-energy particle accelerator at the European Organisation for Nuclear Research (CERN) near Geneva, Switzerland. Proton-proton collisions are recorded and analysed with several large scale detectors, one of them is the Compact Muon Solenoid (CMS) detector. This thesis presents a precision measurement of the top quark pair production cross section in the semi-leptonic electron and jets decay channel with the CMS detector at the LHC. Detailed studies of lepton identification and trigger algorithm efficiencies are summarised as they are crucial for a precise measurement of the production cross section. A maximum likelihood template fit is used to measure the cross section on collision data and an extensive validation of the method is performed. The result of the measurement is sigma(ttbar) = 155.5 +/- 3.7 (stat.) +12.6/-14.8 (syst.) +/- 3.4 (lumi.) pb. A combination method for the measurement in the electron and jets decay channel and an external measurement in the muon and jets decay channel is presented. The mass of the top quark is extracted based on the measured production cross section. All presented measurements are in agreement with the Standard Model predictions.