The inclusive cross section for top quark pair production is measured in protonproton collisions at √s = 7 TeV and √s = 8 TeV with the CMS experiment at the CERN LHC using the full data samples collected in 2011 and 2012. The measurement is performed with events containing an opposite charge electronmuon pair. The cross sections are extracted using a binned likelihood fit to multidifferential final state distributions related to identified b quark and other jets in the event. The measured cross sections are:
σ_{ttbar} = 174.5 ± 2.1 (stat)^{+4.5}_{4.0} (syst) ± 3.8 (lumi) pb at √s = 7 TeV and
σ_{ttbar} = 245.6 ± 1.3 (stat)^{+6.6}_{5.5} (syst) ± 6.5 (lumi) pb at √s = 8 TeV,
in good agreement with recent QCD calculations at nexttonexttoleadingorder precision. The ratio R_{8/7} of the cross sections at the two different values of s is also determined as well as cross sections in a fiducial region σ^{vis}_{ttbar} , defined by the acceptance requirements on the two charged leptons in the final state. The results are:
R_{8/7} = 1.41 ± 0.06,
σ^{vis}_{ttbar} = 3.05 ± 0.04 (stat)^{+0.08}_{0.07} (syst) ± 0.07 (lumi) pb at √s = 7 TeV and
σ^{vis}_{ttbar} = 4.24 ± 0.02 (stat)^{+0.11}_{0.10} (syst) ± 0.11 (lumi) pb at √s = 8 TeV.
The inclusive cross section results are used to determine the top quark pole mass via the dependence of the theoretically predicted cross section on the mass using the NNPDF30 PDF set, giving a result of
m_{t,pole} = 173.6^{+1.7}_{1.8} GeV.
The 8 TeV data are also used to set limits on the pair production of supersymmetric top squarks with masses close to the top quark mass, as a function of the neutralino mass.
The CMS Physics Analysis Summary will soon be made available on CDS.
Figure 1a: Distributions of pt of the leading lepton, after the eμ selection, for the 8 TeV data. The hatched bands correspond to the total uncertainty on the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown at the bottom of each plot. Here, the solid band represents the contribution of the statistical uncertainty. PDF  PNG 

Figure 1b: Distributions of η of the leading lepton, after the eμ selection, for the 8 TeV data. The hatched bands correspond to the total uncertainty on the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown at the bottom of each plot. Here, the solid band represents the contribution of the statistical uncertainty. PDF  PNG 

Figure 1c: Distributions of pt of the secondleading lepton, after the eμ selection, for the 8 TeV data. The hatched bands correspond to the total uncertainty on the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown at the bottom of each plot. Here, the solid band represents the contribution of the statistical uncertainty. PDF  PNG 

Figure 1d: Distributions of η of the secondleading lepton, after the eμ selection, for the 8 TeV data. The hatched bands correspond to the total uncertainty on the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown at the bottom of each plot. Here, the solid band represents the contribution of the statistical uncertainty. PDF  PNG 

Figure 2a: Distributions of pt of the leading lepton, after the eμ selection, for the 8 TeV data. The hatched bands correspond to the total uncertainty on the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown at the bottom of each plot. Here, the solid band represents the contribution of the statistical uncertainty. PDF  PNG 

Figure 2b: Distributions of η of the leading lepton, after the eμ selection, for the 8 TeV data. The hatched bands correspond to the total uncertainty on the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown at the bottom of each plot. Here, the solid band represents the contribution of the statistical uncertainty. PDF  PNG 

Figure 2c: Distributions of pt of the secondleading lepton, after the eμ selection, for the 8 TeV data. The hatched bands correspond to the total uncertainty on the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown at the bottom of each plot. Here, the solid band represents the contribution of the statistical uncertainty. PDF  PNG 

Figure 2d: Distributions of η of the secondleading lepton, after the eμ selection, for the 8 TeV data. The hatched bands correspond to the total uncertainty on the sum of the predicted yields. The ratios of data to the sum of the predicted yields are shown at the bottom of each plot. Here, the solid band represents the contribution of the statistical uncertainty. PDF  PNG 

Figure 3a: Distribution of the b jet multiplicity after the eμ selection for 8 TeV. Other details as for Figure 1. PDF (lin)  PNG (lin) PDF (log)  PNG (log) 

Figure 3b: Distribution of the b jet multiplicity after the eμ selection for 7 TeV. Other details as for Figure 1. PDF (lin)  PNG (lin) PDF (log)  PNG (log) 

Figure 4a: Total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with zero or more than two btagged jets at √s = 8 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 4b: Total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with one btagged jets at √s = 8 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 4c: Total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with two btagged jets at √s = 8 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 5a: Total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with zero or more than two btagged jets at √s = 7 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 5b: Total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with one btagged jets at √s = 7 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 5c: Total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with two btagged jets at √s = 7 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 6a: Fitted total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with zero or more than two btagged jets at √s = 8 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 6b: Fitted total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with one btagged jets at √s = 8 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 6c: Fitted total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with two btagged jets at √s = 8 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 7a: Fitted total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with zero or more than two btagged jets at √s = 7 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 7b: Fitted total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with one btagged jets at √s = 7 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 7c: Fitted total event yield for zero additional nonbtagged jets (left) and p_{T} of the least energetic additional non btagged jet in the event (right) for events with one, two, and at least three additional non btagged jets, and with two btagged jets at √s = 7 TeV. The hatched bands correspond to the sum of statistical and systematic uncertainties in the event yield for the sum of signal and background predictions. The ratios of data to the sum of the predicted yields are shown at the bottom of each subplot. Here, the solid band represents the statistical uncertainty. PDF  PNG 

Figure 8a: Distribution of the b jet multiplicity for the cross check analysis after the final event selection including two jets at 8 TeV. Other details as for Figure 1. PDF  PNG 

Figure 8b: Distribution of the b jet multiplicity for the cross check analysis after the final event selection including two jets at 7 TeV. Other details as for Figure 1. PDF  PNG 

Figure 9a: Predicted dependence of the ttbar production cross section on the top quark mass for 7 TeV. The calculation is performed at NNLO+NNLL accuracy using the TOP++ program, for α_{S} =0.118±0.001, and the parton distribution function NNPDF30. PDF  PNG 

Figure 9b: Measured dependence of the ttbar production cross section on the top quark mass for 7 TeV. The total 1σuncertainty is indicated by black lines and the measured points by black symbols. PDF  PNG 

Figure 9c: Predicted dependence of the ttbar production cross section on the top quark mass for 8 TeV. The calculation is performed at NNLO+NNLL accuracy using the TOP++ program, for α_{S} =0.118±0.001, and the parton distribution function NNPDF30. PDF  PNG 

Figure 9d: Measured dependence of the ttbar production cross section on the top quark mass for 8 TeV. The total 1σuncertainty is indicated by black lines and the measured points by black symbols. PDF  PNG 

Figure 10a: Combined likelihood of the measured and predicted dependence of the ttbar production cross section on the top quark mass for 7 TeV (right). The total 1σuncertainty is indicated by a black contour. PDF  PNG 

Figure 10b: Combined likelihood of the measured and predicted dependence of the ttbar production cross section on the top quark mass for 8 TeV (right). The total 1σuncertainty is indicated by a black contour. PDF  PNG 

Figure 12a: Expected and observed limits at 95% CL on the signal strength as a function of the stop quark mass for a neutralino mass of 1 GeV. PDF  PNG 

Figure 12b: Expected and observed limits at 95% CL on the signal strength as a function of the stop quark mass for a neutralino mass of 12.5 GeV. PDF  PNG 
Table 1: Number of selected eμ events for the event counting method for the 7 and 8 TeV datasets. The results are given for the individual sources of background, ttbar signal and data. The uncertainties correspond to the statistical and systematic components. PDF  PNG 

Table 2: Assumed correlations ρ between systematic uncertainties for the 7 TeV and 8 TeV data sets. If ρ = 0 the uncertainties are treated as uncorrelated between the two sets. PDF  PNG 

Table 3: Illustrative summary of the individual contributions to the total uncertainty on the visible ttbar cross section measurements. The uncertainties are given in percentages. PDF  PNG 

Table 4: Individual contributions to the systematic uncertainty on the total ttbar cross section measurements. The uncertainties are given in percentages. The total systematic uncertainties on the fiducial cross sections σvis are given in the row “Total (vis)” and those on the full phase ttbar space parton level cross section σ_{ttbar} in the row “Total”. PDF  PNG 

Table 5: Top quark pole mass at NNLO+NNLL extracted by confronting the measured ttbar production cross section at 7 and 8 TeV with predictions employing different PDF sets. PDF  PNG 

Table 6: Combined top quark pole mass at NNLO+NNLL extracted by confronting the measured ttbar production cross section with predictions employing different PDF sets. PDF  PNG 
 AndreasMeyer  20150825