TOP-11-024: Combination of top quark pair production cross section measurements

Abstract

We present a combination of the measurements of the pp → ttbar production cross section at sqrt(s)=7 TeV using data collected by the CMS detector at the Large Hadron Collider. The channels included in the combination are single lepton (e, mu), dilepton (ee, mumu, emu), tau (mu tau), and fully hadronic decays. The analyses use data corresponding to an integrated luminosity between 0.8 and 1.1 fb^-1. A binned maximum likelihood fitter is used for the combination. We find a combined cross section of 165.8 ± 2.2 (stat.) ± 10.6 (syst.) ± 7.8 (lumi.) pb.

Public results for the individual channels in the combination

The individual measurements that enter this combination have already been summarized in the following public documents

Date ID Analysis Luminosity Public Webpage CDS Document
September 2011 TOP-11-003 Top pair cross section in lepton+jets+btag 0.8-1.1/fb link CMS PAS TOP-11-003
August 2011 TOP-11-005 Top pair cross section in dilepton channel 1.1/fb link CMS PAS TOP-11-005
July 2011 TOP-11-006 Top pair cross section in tau dilepton channel 1.1/fb link CMS PAS TOP-11-006
July 2011 TOP-11-007 Top pair cross section in hadronic channel 1.1/fb link CMS PAS TOP-11-007

Approved results from TOP-11-024 (click on result to get .png)

Result Description
Final result from likelihood fit PDF
Cross check: BLUE combination PDF

Approved plots and tables (click on image to get .png)

Figure Abbreviated caption
Table1.png Table 1: Summary of measurements in individual channels. PDF
Table2.png Table 2: Summary of background uncertainties. Size of 1 sigma variation in the various background systematic uncertainties for the channels in the combination. The uncertainties are expressed in percentage of individual background normalizations. PDF
Table3.png Table 3: Summary of systematic uncertainties. Size of 1 sigma variation in the various ttbar acceptance systematic uncertainties for the channels in the combination. For the single lepton channels, the dependencies are either a flat percentage or are parameterized by a polynomial, one for each(jet,tag) subsample. The entries are given in percentage change to the \ttbar acceptance. Note the W+jets Q^2 uncertainty in the single lepton analysis only affects the normalization of the W+jets templates, but we list it in the table for completeness. PDF
Figure1.png Figure 1: Summary of CMS measurements and their combination overlaid with three theory predictions PDF

-- AmandaDeisher - 09-Nov-2011

Topic attachments
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PDFpdf Equation10.pdf r1 manage 15.0 K 2011-11-09 - 15:48 UnknownUser  
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Topic revision: r8 - 2011-11-30 - FrankPeterSchilling
 
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