Measurement of the Top dilepton pair production cross section

using the lepton & track data set

CDF Authors

J.Incandela °, P. Merkel¤, C. Mills°, P.Savard ¹, T. Spreitzer¹, J. Thom§, P. Wittich²

§Fermi National Accelerator Laboratory, ¤Purdue University, °University of California, Santa Barbara, ²University of Pennsylvania, ¹University of Toronto

The Analysis

In this 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 signature for our data set is two leptons, two or more jets and missing energy. We use tight lepton idenficiation on the first lepton and only require loose lepton id on the second leg to gain acceptance overall and to hadronic tau decays.Our data set consists of 360 /pb collected during Run 2 at the Fermilab Tevatron at a center of mass energy of √ s = 1.96 TeV.

We extract the central value of the cross - section from the sample with the kinematic thresholds of jet E_t > 20 GeV and isolated track transverse momentum > 20 GeV / c.The opposite charge requirement is applied.We observe 46 candidate events satisfying that selection, with a predicted background of 14.64 ± 3.55.We measure a cross - section of

σ = 9.85 ± 2.13(stat) ± 1.30(sys) ± 0.59(lumi) pb.

assuming BR(W → l ν ) = 10.8 % and m_top = 178 GeV / c ^ 2.

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

Numbers of events expected from signal, physics backgrounds and fakes and the number of observed events in 360 / pb of data. Errors are statistical and systematic.
n(jet) = 0 n(jet) = 1 n(jet) ≥ 2
Di boson 34.29 ± 6.11 6.97 ± 1.26 1.96 ± 0.37
DY 48.13 ± 19.60 32.19 ± 11.52 8.71 ± 3.31
Fakes 40.79 ± 12.40 11.77 ± 3.58 3.96 ± 1.21
Total bg 123.21 ± 24.04 50.93 ± 12.17 14.64 ± 3.55
t tbar 0.32 ± 0.03 5.19 ± 0.37 19.42 ± 1.35
Total pred. 123.53 ± 24.04 56.12 ± 12.21 34.05 ± 3.89
observed 121 63 46
Tables are also available in GIF format for easy inclusion in your talk.

Supporting material

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