Measurement of the Top Dilepton Pair Production Cross-Section

The Analysis

We measure the top pair production cross section where top decays to a W boson and a b quark ( t → Wb ), and both W bosons in turn decay leptonically. The candidate sample is events with two opposite-sign leptons, two or more jets, and significant missing transverse energy (MET). We fully reconstruct the first lepton but only require the second lepton to be identified as an isolated track. This increases the top acceptance by including leptons that may not be fiducial to calorimetry or muon detectors, and most decay channels (including "1-prong" hadronic) of tau leptons.

The primary backgrounds in the candidate sample are diboson (WW,WZ,ZZ), Drell-Yan (Z/γ*→ee/μμ/ττ), and W+jets events, where one of the jets associated with the W is identified as an isolated track. The diboson and Z/γ*→ττ backgrounds are estimated using the acceptance calculated from Monte Carlo and normalized using the theoretical cross-sections. We normalize the Drell-Yan ee/μμ contribution using high-MET events in the data after subtracting contributions from other sources, and use Monte Carlo to distribute the events according to invariant mass and number of jets. For the W + fake lepton background, we multiply the W + jets spectrum by a lepton fake rate derived from jets in high-transverse-momentum photon data.

The top acceptance for lepton plus isolated track events is 0.845 ± 0.026%. In 1.07 fb-1 of data collected during Run 2 at the Fermilab Tevatron at a center of mass energy of √ s = 1.96 TeV, we observe 129 candidate events, with a predicted background of 54.0 ± 6.6. We measure a cross-section of

σ = 8.3 ± 1.3(stat) ± 0.7(sys) ± 0.5(lumi) pb.

assuming BR(W → l ν) = 10.8 % and m_top = 175 GeV / c ^ 2.

Overview table of control (n(jet)≤1) and signal (n(jet)≥2) regions

Additional figures and tables

• Kinematic distributions
• Tables (detailed predicted vs. observed, cross-section vs. mass)

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