This thesis presents two measurements of the top quark pair production cross section at √ s = 1.96 TeV using data from the DØ experiment. Both measurements are performed in the dilepton final state and make use of secondary vertex b-tagging. With 158 pb −1 of data in the eµ final state, the measured cross section is:With 425 pb −1 of data in the e + track and µ + track final states, the measured cross section is:Both measurements are in agreement with the prediction from perturbative QCD calculations.In addition, an estimate of the DØ silicon detector lifetime is presented. The radiation damage is determined by studying the depletion voltage of the silicon sensors as a function of time. Based on this data the silicon detector is estimated to remain operational up to delivered luminosities of 6-8 fb Cover image courtesy of Fermilab Visual Media Services, the DØ Collaboration and Jan-Henrik Andersen.iii The work presented in this thesis is published in the following papers:I Measurement of the tt Production Cross Section in pp Collisions Using Dilepton EventsThe DØ CollaborationTo be submitted to Phys. Rev. D, currently in DØ editorial board review II Measurement of the tt production cross-section at √ s = 1.96 TeV in the combined lepton+track and eµ channel using 370 pb −1 of DØ data Sara Lager for the DØ Collaboration