CDF Logo Measurement of WW and WZ production in the lepton+Heavy Flavor jets channel in the full CDFII dataset
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Abstract:

We present the measurement of the diboson WW and WZ associate production in a final state consistent with semileptonic W decay plus heavy flavor quarks. This analysis uses the full dataset, collected with the CDF II detector at the Tevatron p-pbar collider and corresponding to an integrated luminosity of approximately 9.4 fb-1. Candidate signal events are required to have one charged lepton, kinematics consitent with the W→lnu decay and two high ET jets containing at least one secondary-decay vertex signaling the presence of heavy flavor hadrons. The analysis of the di-jet invariant mass spectrum allows to observe a 3.69 s.d. evidence of the WW+WZ production in this final state and to extract a cross section measurement of σWW+WZ = 13.7 +/- 3.9 pb. The different heavy flavor decay pattern of the W and Z bosons (e.i. W→cs, Z→ b-bbar,c-cbar) and the analysis of the secondary-decay vertex properties allow to independently measure the WW and WZ production cross section in a hadronic final state, for the first time at hadron colliders. The measured cross sections of σWW= 9.4 +/- 4.2 pb and σWZ=3.7+2.5-2.2 pb are consistent with the SM predictions and correspond to a signal significances of 2.87 s.d. and 2.12 s.d. for WW and WZ respectively.


Results:   WW and WZ cross section measurements  &   Invariant mass/Flavor-separator NN distributions
Estimation of W+HF correction factor from W+1jet sample  


Validation of kinematic distributions:
Pretag W + 2 jets, control sample   1 tag W + 2 jets, signal sample   2 tags W + 2 jets, signal sample  
Pretag W + 1 jet, control sample   1 tag W + 1 jet, signal sample for W+HF correction extraction  


Examples of multi-jet estimate with fit of the SVM discriminant:

Pretag W + 2 jets   1 tag W + 2 jets   Pretag W + 1 jet   1 tag W + 1jet  

2-Dimentional discrimination: Mj1j2 vs Flavor-separator NN:

Signals (WW, WZ) and two relevant backgrounds (W+c, W+bb)  

 

Supporting Documents:

  • More details are provided in the public note

  • General Remarks:

  • These results were blessed by the CDF Physics group in March, 2015
  • An accurate description of the analysis strategy, techniques, and preliminary results from 2012 are availale here: PhD Thesis
  • Please contact us if you have any questions about including these results in a presentation
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