Measurement of the Top Quark Pair Production Cross Section in 7 TeV pp Collisions

In this thesis we present the measurement of the top quark pair production cross section in pp collisions at a center of mass energy of 7 Te V, using 36 $pb^{-1}$ of data collected with the CMS experiment at the LHC. The selection of the data sample is based on the final state with one isolated, high transverse momentum muon, missing transverse energy and at least three hadronic jets. The $t\overline{t}$ content of the selected sample is enhanced by requiring the presence of at least one jet consistent with b-quark hadronization. The measured cross section: $\sigma_{t\overline{t}}$ = 153.7 $\pm$ 9.0(stat.)$^{+28.2}_{-24.4}$(syst.) $\pm$ 6.1(lumi) pb is in good agreement with higher-order QCD calculations for a top quark of mass mt = 173 GeV /$c^{2}$ (1).