Measurement of the ttbar Cross Section in the Lepton + Jets Channel Using Event Kinematics




Authors:
R. Hughes, R. Marginean, E. Thomson, B. Winer
The Ohio State University

R. Erbacher, R. Roser
Fermi National Accelerator Laboratory

J. Conway
Rutgers University


CDF Public conference Note 7154.


195/pb Plots and Tables:
Link to Previous Results with 126/pb shown at Lepton Photon 2003

Results with 195 /pb, having used HT as our kinematic variable to discriminate top from background. HT is the scalar sum of transverse energies of the lepton and the jets, and the missing transverse energy. The large mass of the top quark makes HT a good discriminating variable between top pair production and background processes. The event selection requires an isolated, highly energetic identified lepton (electron ET>20 GeV, muon PT>20 GeV), missing transverse energy > 20 GeV and three of more jets with ET>15 GeV.


Table showing number of events in data, ttbar fraction, and resulting cross section with statistical errors listed first, systematic errors listed second.  (EPS)

Final Fits to the Signal Region:

Our primary result is using HT for the 3 or more jet bin.   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 data non-isolated leptons and fixed to 6.3%.  The ttbar and W-like shapes float in the fits. 

W + 3 or More Jet Sample

W + 4 or More Jet Sample


Fit to HT (gif) for at least 3 jets, showing stacked contribution of each component (EPS) (TIF)

Fit to HT (gif) for at least 4 jets, showing stacked contribution of each component (EPS) (TIF)

Fit results are fairly stable across a range of kinematic variables for events with 3 or more jets. The vertical bar corresponds to the cross section measurement made with a 7 input variable ANN in the 3 ore more jets data sample.(EPS)


Fit results are fairly stable across a range of kinematic variables for events with 4 or more jets. The vertical bar corresponds to the cross section measurement made with a 7 input variable ANN in the 3 ore more jets data sample. (EPS)



Last modified on 03/14/05 by Radu Marginean