Top Pair Production Cross Section with Tight SecVtx Tags using 318 pb-1  
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S. Rappoccio, J. Guimaraes da Costa, D. Sherman, A. Foland, M. Franklin,
Harvard University
CDF

Result (318 pb-1): 8.7 +0.9-0.9 (stat) +1.2-0.9 (syst) pb (for mtop = 178 GeV/c2)

Summary
We measured the ttbar pair production cross section in the lepton plus jets channel with >=1 and >= 2 secondary vertex tag.  We require an isolated electron or muon with transverse momentum above 20 GeV, missing transverse energy greater than 20 GeV and three or more jets with transverse energy above 15 GeV. In addition,  we require that one or more of the jets are tagged with a displaced secondary vertex, indicating the presence of heavy flavor in the jet. The signal expectation is determined from a simulation that assumes the top mass to be 178 GeV/c2.

The default optimized measurement uses the transverse mass of the leptonic W-boson to reduce the Non-W background and the scalar sum of transverse energies of the event (HT) to discriminate ttbar from the other backgrounds. As a cross check, we have measured the cross section using a fit to the number of jets spectrum in the W + jets data; and without the Mt and Ht cuts (unoptimized analysis). This result uses 318 pb-1 of CDF run II data.


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W+ >= 3 jets Optimized
>= 1 b-tag
 8.7 +0.9-0.9 (stat) +1.2-0.9(syst) pb
>= 2-btags
 8.7 +1.8-1.6 (stat) +1.9-1.3(syst) pb
Cross Check Measurements
W+ >= 3 jets Optimized: Fit to number of jet distribution
1 b-tag + >=2 tags  8.9+0.9-0.9 (stat) +1.4-1.3 (syst) pb
W+ >= 3 jets Unoptimized
>= 1 b-tag 8.9 +1.0-0.9 (stat) +1.2-0.9(syst) pb
>= 2-btags 8.2 +1.7-1.5 (stat) +2.0-1.5(syst) pb
Top Mass Dependence

The acceptance calculation for these results assumes that the top mass is 178 GeV, the currently published world average. The dependence on the input top mass is shown in the figures below, centered on masses of 178 GeV and 175 GeV.


EPS


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Center-of-Mass Energy Dependence

This measurement is done for sqrt(s) = 1.96 TeV. This is the dependence on center-of-mass energy.


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Background Estimate for Optimized Analysis


Background Estimate for Unoptimized Cross-Check Analysis


Plots
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W+ >= 3 jets Optimized Top Cross Section

The expected number of W+jets tagged events categorized by source (solid histogram) and the total number from data (points) binned in number of jets. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
 EPS
The expected number of W+jets double-tagged events categorized by source (solid histogram) and the total number from data (points) binned in number of jets. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS
W+ >= 3 jets Optimized: Fit to number of jet distribution

The expected number of W+jets tagged events categorized by source (solid histogram) and the total number from data (points) binned in number of jets. The top prediction is scaled to our measured value of 8.9 pb. The measurement is only based on events with 3 or more jets.
EPS
The expected number of W+jets double-tagged events categorized by source (solid histogram) and the total number from data (points) binned in number of jets. The top prediction is scaled to our measured value of 8.9 pb. The measurement is only based on events with 3 or more jets.
EPS
W+ >= 3 jets Unoptimized

The expected number of W+jets tagged events categorized by source (solid histogram) and the total number from data (points) binned in number of jets. The top prediction is scaled to our measured value of 8.9 pb. The measurement is only based on events with 3 or more jets.
EPS
The expected number of W+jets double-tagged events categorized by source (solid histogram) and the total number from data (points) binned in number of jets. The top prediction is scaled to our measured value of 8.2 pb. The measurement is only based on events with 3 or more jets.
Event Display

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W+ >= 3 jets Optimized, Kinematic Plots

The expected number of W+jets tagged events categorized by source (solid histogram) and the total number from data (points) binned in Ht, the scalar sum of transverse energies. The top prediction is scaled to our measured value of 8.9 pb. The measurement is only based on events with 3 or more jets. We cut at 200 GeV for the optimized analysis.
EPS
The expected number of W+jets tagged events categorized by source (solid histogram) and the total number from data (points) binned in Mt, the transverse mass of the leptonic W boson. The top prediction is scaled to our measured value of 8.9 pb. The measurement is only based on events with 3 or more jets. We cut at 20 GeV for the optimized analysis.
EPS

The expected number of W+jets tagged events categorized by source (solid histogram) and the total number from data (points) binned in missing Et. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS
The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in jet Et. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS

The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in jet pseudorapidity. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
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The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in jet azimuthal angle. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
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The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in number of tracks in the jet. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS
The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in vertex pseudo-ct. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS

The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in vertex 2-d decay length. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS
The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in vertex 2-d decay length significance . The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS

The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in vertex momentum. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS
The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in vertex mass. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS

The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in vertex radius from the center of the SVX. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
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The expected number of W+jets tagged jets categorized by source (solid histogram) and the total number from data (points) binned in vertex chi2. The top prediction is scaled to our measured value of 8.7 pb. The measurement is only based on events with 3 or more jets.
EPS