Measurement of the top quark pair production cross section and simultaneous extraction of the W heavy flavor fraction at $\sqrt{s}$ = 7 TeV with the ATLAS detector at the LHC

The top quark pair production cross section, $\sigma_{t\bar{t}}$, is measured in the semileptonic channel in two datasets using a binned profiled likelihood template fit to data to discriminate the signal, $t\bar{t}$, from its main background, the production of a $W$-boson in association with jets ($W$+jets). Templates in the first analysis are derived from a four variable flavor-sensitive discriminant to measure $\sigma_{t\bar{t}}$ in $\int \mathcal{L}dt$= 35 pb$^{-1}$. A similar but flavor-insensitive discriminant is then used to measure $\sigma_{t\bar{t}}$ in $\int \mathcal{L}dt$= 0.7 fb$^{-1}$. A third analysis is presented which simultaneously fits the fractions of $t\bar{t}$ and $W$+jets events in which heavy flavor jets are produced, using a single flavor-sensitive distribution in the $\int \mathcal{L}dt$= 0.7 fb$^{-1}$ dataset. Experimental precision of the top quark pair production cross section surpasses the theoretical uncertainty. No significant deviations from predictions are found but the results are higher than expectation.