Combination of Top Pair Production Cross Section Results

Combination of Top Pair Production Cross Section Results

Conference note for the 4.6 fb-1 combination (9913)

We combine four results using up to 4.6 fb-1 of data:

We use the BLUE method (see conference note for references), where we account for statistical and systematic correlations between the results. In case of asymmetric uncertainties, we take the average of the positive and negative uncertainties.

We find the top quark pair production cross section to be:
7.50 +-0.31(stat) +-0.34(syst)+-0.15(Z theory + Lumi residual) pb = 7.50+- 0.48 pb
where we assume a top quark mass of 172.5 GeV.
The relative uncertainty is 6.4%. The improvement in combining 4 measurements relative to the single best measurement (ANN) is 9%.

eps
Combination of Preliminary Results, when we assume a top quark mass of 172.5 GeV. For each measurement, the statistical uncertainty is shown by the magenta line, which is superimposed on the total uncertainty including systematic and luminosity uncertainties as shown by the black line. We find excellent agreement with the theoretical prediction of 7.46+0.66-0.80 pb from [1] using CTEQ6.6 for a top quark mass of 172.5 GeV and centre-of-mass energy of 1.96 TeV. Note that the scale and PDF uncertainties have been added linearly here.

eps
Combination of Preliminary Results compared to theoretical predictions as a function of sqrt{s}. At sqrt(s)=1960 GeV, the central values of the predictions from [1] are shown at a top quark mass of 170. 172.5 and 175 GeV for CTEQ6.6. The uncertainty (due to scale and PDF variations) of the 172.5 CTEQ6.6 prediction is shown by the filled blue region. At sqrt(s)=1800 GeV, the predictions are shown at a top quark mass of 170 and 175 GeV for CTEQ6M.

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Combination of Preliminary Results compared to theoretical predictions[1,2,3] as a function of top quark mass. A top quark mass value of 172.5 GeV is assumed for the experimental result. The theoretical curves use CTEQ6.5 (Cacciari [2]) or CTEQ6.6 [1,3]. There are three curves for each theory, the middle curve shows the central prediction, while the upper and lower curves show the range of the prediction given scale and PDF uncertainties.

Reference [1] U. Langerfeld, S. Moch and P. Uwer, arXiv:0906.5273(2009); S. Moch and P. Uwer arXiv:0807.2794, and arXiv:0804.1476 (2008).
Reference [2] M.Cacciari, S. Frixione, G. Ridolfi, M. Mangano and P. Nason, arXiv:0804.2800; ibid, JHEP 404, 68 (2004).
Reference [3] N. Kidonakis and R. Vogt, arXiv:0805:3844 (2008); ibid, Phys. Rev. D 68, 114014 (2003).
Previous combinations

Conference note for the 2.8 fb-1 combination (9448)

2008, 2006 and 2005

Questions? Contact us!
Evelyn Thomson (University of Pennsylvania,
Charles Plager (University of California at Los Angeles),
Richard Hughes (The Ohio State University)

	eps Combination of Preliminary Results, when we assume a top quark mass of 172.5 GeV. For each measurement, the statistical uncertainty is shown by the magenta line, which is superimposed on the total uncertainty including systematic and luminosity uncertainties as shown by the black line. We find excellent agreement with the theoretical prediction of 7.46+0.66-0.80 pb from [1] using CTEQ6.6 for a top quark mass of 172.5 GeV and centre-of-mass energy of 1.96 TeV. Note that the scale and PDF uncertainties have been added linearly here.
	eps Combination of Preliminary Results compared to theoretical predictions as a function of sqrt{s}. At sqrt(s)=1960 GeV, the central values of the predictions from [1] are shown at a top quark mass of 170. 172.5 and 175 GeV for CTEQ6.6. The uncertainty (due to scale and PDF variations) of the 172.5 CTEQ6.6 prediction is shown by the filled blue region. At sqrt(s)=1800 GeV, the predictions are shown at a top quark mass of 170 and 175 GeV for CTEQ6M.
	eps Combination of Preliminary Results compared to theoretical predictions[1,2,3] as a function of top quark mass. A top quark mass value of 172.5 GeV is assumed for the experimental result. The theoretical curves use CTEQ6.5 (Cacciari [2]) or CTEQ6.6 [1,3]. There are three curves for each theory, the middle curve shows the central prediction, while the upper and lower curves show the range of the prediction given scale and PDF uncertainties.