Measurement of the inclusive $t\overline{t}$ production cross section in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ and determination of the top quark pole mass

The inclusive cross section of top quark-antiquark pairs produced in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ is measured in the $\text{lepton}+\mathrm{jets}$ and dilepton decay channels. The data sample corresponds to $9.7{\mathrm{fb}}^{-1}$ of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Employing multivariate analysis techniques we measure the cross section in the two decay channels and we perform a combined cross section measurement. For a top quark mass of 172.5 GeV, we measure a combined inclusive top quark-antiquark pair production cross section of ${\sigma }_{t\overline{t}}=7.26\pm 0.13(\mathrm{stat}{)}_{-0.50}^{+0.57}(\mathrm{syst})\mathrm{pb}$ which is consistent with standard model predictions. We also perform a likelihood fit to the measured and predicted top quark mass dependence of the inclusive cross section, which yields a measurement of the pole mass of the top quark. The extracted value is $m_t=172.8\pm 1.1(\mathrm{theo}{)}_{-3.1}^{+3.3}(\exp )\mathrm{GeV}$.

Figure 1

Distributions of (a)–(c) the scalar sum of the $p_T$ values of the lepton and jets, $H_T$, (d)–(f) ${\cancel{E}}_T$ and (g)–(i) the maximal MVA $b$-ID value of all jets, $j_{\mathrm{b}-\mathrm{ID}}^{\max }$, for events with a lepton and two, three or four or more jets. The data are compared to the sum of predicted contributions from signal and background processes, using the theoretical value of the inclusive $t\overline{t}$ cross section of 7.48 pb [37] and $m_t=172.5\mathrm{GeV}$. The highest bin in the histograms includes overflows. The ratios of data to the sum of the signal and all background contributions are shown in the panels below the individual distributions. Only statistical uncertainties of the data are shown and the ${\chi }^2/\mathrm{ndf}$ values only take statistical uncertainties into account.

Figure 2

Distributions of (a)–(c) the transverse mass of the $\text{lepton}+{\cancel{E}}_T$ system, $m_T^W$, and (d)–(f) $p_T^{\text{lepton}}$ for events with a lepton and two, three or four or more jets. The data are compared to the sum of predicted contributions from signal and background processes, using the theoretical value of the inclusive $t\overline{t}$ cross section of 7.48 pb [37] and $m_t=172.5\mathrm{GeV}$. The highest bin in the histograms includes overflows. The ratios of data to the sum of the signal and all background contributions are shown in the panels below the distributions. Only statistical uncertainties of the data are shown and the ${\chi }^2/\mathrm{ndf}$ values only take statistical uncertainties into account.

Figure 3

Distributions of (a) the scalar sum, $H_T$, of the $p_T$ values of the leading lepton and leading and second-leading jets, (b) ${\cancel{E}}_T$, (c) $j_{\mathrm{b}-\mathrm{ID}}^{\max }$, (d) the number of jets, and (e) lepton $p_T$ for $\ell \ell$ final states with at least one jet in the $e\mu$ and at least two jets in the $ee$ and $\mu \mu$ channels. The data are compared to the sum of predicted contributions from signal and background processes, using the theoretical value of 7.48 pb for the $t\overline{t}$ cross section and $m_t=172.5\mathrm{GeV}$. The highest bin in the histograms includes overflows. The ratios of data to the sum of the signal and all background contributions are shown in the panels below the distributions. Only statistical uncertainties of the data are shown and the ${\chi }^2/\mathrm{ndf}$ values only take statistical uncertainties into account.

Figure 4

Signal efficiency vs background rejection for different MVA choices for the $e+3$ jets sample. For details, see text in Sec. 7. The dashed line from (0,1) to (1,0) is shown for reference.

Figure 5

Pre-fit output distributions of the combined MVA discriminant using the theoretical $t\overline{t}$ cross section and $m_t=172.5\mathrm{GeV}$ for the $e+$ two, three or four or more jets [panels (a)–(c)], and for the $\mu +$ two, three or four or more jets [panels (d)–(f)]. Statistical uncertainties of the data are shown and the pre-fit systematic uncertainties are indicated by the hashed band in the bottom panel of the histogram. The ${\chi }^2/\mathrm{ndf}$ values take statistical and systematic uncertainties into account.

Figure 6

The pre-fit MVA output distributions (using the theoretical $t\overline{t}$ cross section and $m_t=172.5\mathrm{GeV}$) of the $b$-ID MVA given by the jet with the maximum value, $j_{\mathrm{b}-\mathrm{ID}}^{\max }$, for (a) $e\mu$ events with exactly one jet, (b) $e\mu$ events with at least two jets, (c) $ee$ events with at least two jets, and (d) $\mu \mu$ events with at least two jets. Statistical uncertainties of the data are shown and the pre-fit systematic uncertainties are indicated by the hashed band in the bottom panel of the histogram. The ${\chi }^2/\mathrm{ndf}$ values take statistical and systematic uncertainties into account.

Figure 7

Post-fit output distributions of the combined MVA discriminant using the measured combined $t\overline{t}$ cross section and $m_t=172.5\mathrm{GeV}$ for the $e+$ two, three or four or more jets [panels (a)–(c)], and for the $\mu +$ two, three or four or more jets [panels (d)–(f)]. Statistical uncertainties of the data are shown and the post-fit systematic uncertainties are indicated by the hashed band in the bottom panel of the histogram. The ${\chi }^2/\mathrm{ndf}$ values take statistical and systematic uncertainties into account.

Figure 8

The post-fit MVA output distributions (assuming $m_t=172.5\mathrm{GeV}$) of $j_{\mathrm{b}-\mathrm{ID}}^{\max }$ for (a) $e\mu$ events with exactly one jet, (b) $e\mu$ events with at least two jets, (c) $ee$ events with at least two jets, and (d) $\mu \mu$ events with at least two jets are shown. Statistical uncertainties of the data are shown and the post-fit systematic uncertainties are indicated by the hashed band in the bottom panel of the histogram. The ${\chi }^2/\mathrm{ndf}$ values take statistical and systematic uncertainties into account.

Figure 9

The measured $t\overline{t}$ production cross section dependence on the top quark mass (points) parametrized by a quartic function (solid black line) and compared to the dependence provided by the NNLO pQCD calculation $\mathrm{TOP}++$ [41], which implements pQCD calculations according to Ref. [38].