  We present a measurement of the inclusive top quark pair production cross
section in \ppbar collisions at (\sqrt{s}=1.96) TeV utilizing data
corresponding to an integrated luminosity of \lumi\ collected with the D0
detector at the Fermilab Tevatron Collider. We consider final states containing
one high-$p_{T}$ isolated electron or muon and at least two jets, and we
perform three analyses: one exploiting specific kinematic features of \ttbar
events, the second using $b$-jet identification, and the third using both
techniques to separate \ttbar\ signal from background. In the third case, we
determine simultaneously the $t\bar{t}$ cross section and the ratio of the
production rates of $W$+heavy flavor jets and $W$+light flavor jets, which
reduces the impact of the systematic uncertainties related to the background
estimation. Assuming a top quark mass of 172.5 GeV, we obtain
$\sigma_{t\bar{t}} = 7.78^{+0.77}_{-0.64} $ pb. This result agrees with
predictions of the standard model.
