Measurement of differential $t\overline{t}$ production cross sections in $p\overline{p}$ collisions

The production of top quark-antiquark pair events in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ is studied as a function of the transverse momentum and absolute value of the rapidity of the top quarks as well as of the invariant mass of the $t\overline{t}$ pair. We select events containing an isolated lepton, a large imbalance in transverse momentum, and four or more jets with at least one jet identified as originating from a $b$ quark. 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. Observed differential cross sections are consistent with standard model predictions.

Figure 1

The $|{\mathcal{S}}_c|$ versus $\mathrm{\Delta }\varphi (\mu ,{\cancel{E}}_T)$ plane for (a) $t\overline{t}$ events and (b) for $W+\text{jets}$ background events. The selection requirements are indicated by the solid lines.

Figure 2

Distributions of the MVD $b$ identification output distribution for the $\ell +2$ jets, $\ell +3$ jets and $\ell +\ge 4$ jets data sample in the (a) $e+\text{jets}$ and (b) $\mu +\text{jets}$ decay channel. The data are compared to the sum of predicted contributions from signal and background processes. More details on how the sample composition is derived can be found in the text.

Figure 3

Distributions of (a) the number of jets, (b) the scalar sum of the $p_T$ values of the lepton and jets, (c) ${\cancel{E}}_T$, and (d) lepton $p_T$ for the $e+\text{jets}$ final state. The data are compared to the sum of predicted contributions from signal and background processes. The signal contribution is derived employing mc@nlo simulated events normalized to the measured inclusive $t\overline{t}$ cross section of 8.0 pb. The highest bin in the histograms is used as an overflow bin. The ratios of data to the sum of the signal and all background contributions are shown in the panels below the distributions. The bands show the 1 s.d. combined systematic uncertainties on the sum of the signal and background contributions.

Figure 4

Distributions of (a) the number of jets, (b) the scalar sum of the $p_T$ values of the lepton and jets, (c) ${\cancel{E}}_T$, and (d) lepton $p_T$ for the $\mu +\text{jets}$ final state. The data are compared to the sum of predicted contributions from signal and background processes. The signal contribution is derived employing mc@nlo simulated events normalized to the measured inclusive $t\overline{t}$ cross section of 8.0 pb. The highest bin in the histograms is used as an overflow bin. The ratios of data to the sum of the signal and all background contributions are shown in the panels below the distributions. The bands show the 1 s.d. combined systematic uncertainties on the sum of the signal and background contributions.

Figure 5

Distribution of ${\chi }^2$ for the best solution with lowest ${\chi }^2$ for the (a) $e+\text{jets}$ and (b) $\mu +\text{jets}$ final states. The data are compared to the sum of predicted contributions from signal and background processes. The signal contribution is derived employing mc@nlo simulated events normalized to the measured inclusive $t\overline{t}$ cross section of 8.0 pb. The highest bin in the histograms is used as an overflow bin. The ratios of data to the sum of the signal and all background contributions are shown in the panels below the distributions. The bands show the 1 s.d. combined systematic uncertainties on the sum of the signal and background contributions.

Figure 6

Distribution of $m(t\overline{t})$, (a) compared to the sum of predicted contributions from signal and background processes, and (b) the background-subtracted distribution. The signal contribution is derived employing mc@nlo simulated events normalized to the measured inclusive $t\overline{t}$ cross section of 8.0 pb. The lower panels indicate the ratio of the data to (a) the sum of the signal and all background processes, and (b) to the signal process only.

Figure 7

Distribution of $|y^{\text{top}}|$, (a) compared to the sum of predicted contributions from signal and background processes, and (b) the background-subtracted distribution. The signal contribution is derived employing mc@nlo simulated events normalized to the measured inclusive $t\overline{t}$ cross section of 8.0 pb. The lower panels indicate the ratio of the data to (a) the sum of the signal and all background processes, and (b) to the signal process only.

Figure 8

Distribution of $p_T^{\text{top}}$, (a) compared to the sum of predicted contributions from signal and background processes, and (b) the background-subtracted distribution. The signal contribution is derived employing mc@nlo simulated events normalized to the measured inclusive $t\overline{t}$ cross section of 8.0 pb. The lower panels indicate the ratio of the data to (a) the sum of the signal and all background processes, and (b) to the signal process only.

Figure 9

(a) Measured differential cross section as a function of $m(t\overline{t})$ for data compared to several QCD predictions. The inner error bars correspond to the statistical uncertainties and the outer error bars to the total uncertainties. (b) Ratio of data, alpgen (dashed line) and mc@nlo cross sections (dash-dotted line) to the QCD prediction at approximate NNLO [24]. MC simulations and pQCD predictions use a top quark mass of 172.5 GeV unless indicated to the contrary. Note that the correlated overall normalization uncertainty on the differential data points is about $\pm 6.6\%$.

Figure 10

(a) Measured differential cross section as a function of $|y^{\text{top}}|$ for data compared to several QCD predictions. The inner error bars correspond to the statistical uncertainties and the outer error bars to the total uncertainties. (b) Ratio of data, alpgen (dashed line) and mc@nlo cross sections (dash-dotted line) to the QCD prediction at approximate NNLO [23]. MC simulations and pQCD predictions use a top quark mass of 172.5 GeV unless indicated to the contrary. Note that the correlated overall normalization uncertainty on the differential data points is about $\pm 6.6\%$.

Figure 11

(a) Measured differential cross section as a function of $p_T^{\text{top}}$ for data compared to several QCD predictions. The inner error bars correspond to the statistical uncertainties and the outer error bars to the total uncertainties. (b) Ratio of data, alpgen (dashed line) and mc@nlo cross sections (dash-dotted line) to the QCD prediction at approximate NNLO [14]. MC simulations and pQCD predictions use a top quark mass of 172.5 GeV unless indicated to the contrary. Note that the correlated overall normalization uncertainty on the differential data points is about $\pm 6.6\%$.