Measurement of the $t\overline{t}$ Production Cross Section in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

We present a measurement of the top quark pair production cross section in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ using $318{\mathrm{pb}}^{-1}$ of data collected with the Collider Detector at Fermilab. We select $t\overline{t}$ decays into the final states $e\nu +\mathrm{\text{jets}}$ and $\mu \nu +\mathrm{\text{jets}}$, in which at least one $b$ quark from the $t$-quark decays is identified using a secondary vertex-finding algorithm. Assuming a top quark mass of $178\mathrm{GeV}/c^2$, we measure a cross section of $8.7\pm 0.9(\mathrm{stat}{)}_{-0.9}^{+1.1}(\mathrm{syst})\mathrm{pb}$. We also report the first observation of $t\overline{t}$ with significance greater than $5\sigma$ in the subsample in which both $b$ quarks are identified, corresponding to a cross section of ${10.1}_{-1.4}^{+1.6}(\mathrm{stat}{)}_{-1.3}^{+2.0}(\mathrm{syst})\mathrm{pb}$.

Figure 1

Summary of background and signal event yields versus number of jets in the event when requiring (a) at least one $b$-tagged jet and (b) at least two $b$-tagged jets. The $t\overline{t}$ contribution is normalized to the measured cross section in each sample. The $H_T$ requirement is released for events with fewer than 3 jets. The hashed region shows the uncertainty on the total expectation.