We combine the lepton+jets and dilepton top mass measurements using the leptons’ Pt.

The combination of the top mass measurements and the statistical and systematic uncertainties are derived using the Iterative Best Linear Unbiased Estimator “BLUE”.

The lepton+jets top mass measurement is:

This is the result of the combination of the e+jets and μ+jets measurements:

The dilepton top mass measurement is:

The fits to the 2.8 fb-1 b-tagged lepton+jets and dilepton data are shown in Figures 2 and 3 respectively.

For the combination, the e+jets and μ+jets decay modes of the lepton+jets channel are considered as separate measurements as they have different statistical significance and therefore different weight on the total combination.  The “BLUE” algorithm estimates that the weight of the three measurements is:

we+jets   = 0.42

wμ+jets   = 0.40

wdilepton = 0.18

The combined top mass measurement is:

The statistical uncertainty of the combined measurement is δΜtopstat = 7.2 GeV

The mass dependence of the statistical uncertainty is taken into consideration. The details are found here.

The systematic uncertainty of the combined measurement is δΜtopsyst = 2.3 GeV

The systematic uncertainties and the correlation factors for the combination of the three measurements are found here

The statistical significance of the e+jets, μ+jets and dilepton measurements is shown in Figure 1.

Figure 1:The statistical significance of the the e+jets, μ+jets and dilepton top mass measurements at 2.8 fb-1 using the leptons Pt in comparison to their "BLUE" combination (vertical band). The red color denotes the statistical uncertainties (dominant) and the blue color denotes the total uncertainties.

Figure 2: Fit to the 2.8 fb-1 b-tagged lepton+jets data. The top mass measurement in the fit is before any corrections are applied

Figure 3: Fit to the 2.8 fb-1 b-tagged dilepton data. The top mass measurement in the fit after all corrections are applied

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