Measurement of the ttbar Cross Section in the Lepton + Jets Channel Using Event Kinematics and NN
(Update to 347 pb-1)


R.Hughes, B. Kilminster, K. Lannon,  B. Winer
The Ohio State University

E. Thomson
University of Pennsylvania

R. Roser
Fermi National Accelerator Laboratory

J. Conway, R. Erbacher
University of California-Davis


Public Web Page with Blessed Plots

Documentation (347 pb-1):

CDF Note 7563
Blessing Talk [ pdf | ppt ]
Preblessing Talk [ pdf | ppt ]
Questions since the Preblessing
Changes since the Preblessing
Questions since the Blessing
Blessing Talk for b-tagged NN output [ pdf | ppt]

Documentation (195 pb-1):

CDF Note 6897
CDF Note 6802
Kinematic HT Cross Section Analysis.
Neural Net Cross Section Analysis.



Final Results for 347pb-1:



Sample
Number of Events
ttbar Fraction
Cross Section
W + 3 or More Jets
936
15.8 ± 2.2%
6.0 ± 0.8 ± 1.0 pb
W + 4 or More Jets
210
38.5 ± 7.1%
6.1 ± 1.1 ± 1.4 pb
Table showing number of events in data, ttbar fraction, and resulting cross section with statistical errors listed first, systematic errors listed second.

Final Fits to NN Output Shape:

Fits for a 347-1 pb data sample follow bellow.  The W-like shapes include the contribution from W+3p, Wbbar+1p, Z->ll (3 flavors), W->tau nu+2p, WW+1p, WZ, single top.  Electrons and muons have been combined for the fits.  The QCD shape is taken from the non-isolated leptons and fixed to 4.6% from our MET v. Isolation calculations.  The ttbar and W-like shapes float in the fits.  Based on apriori sensitivity expectations, our primary result is for the 3 or more jet bin.

W + 3 or More Jet Sample

W + 4 or More Jet Sample

W+ >= 3 jets fit
Fit to the NN-output shape for at least 3 jets, showing shapes of contributing components (EPS)
W+ >= 4 jets fit
Fit to the NN-output shape for at least 3 jets, showing shapes of contributing components (EPS)


A look ahead to the next generation . . . (maybe not Gen6)

Last modified on 04/20/05 by Kevin Lannon