ww_dilepton

Measurement of the W+W- Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Dilepton Events

S. Cabrera, S. Carron, S. Chuang, J. Deng, A. Goshaw, Y. Huang, M. Kruse, D. McGivern, D.Waters

For further details on all of the below, please refer to the published article.

[CDF ONLY : analysis details can be found in CDF-6909]

Physics Background
The measurement of the W pair production cross-section at the Tevatron provides an important test of the Standard Model. Leading order t-channel (~90%) and s-channel (~10%) diagrams are :

Anomalous WW-gamma or WWZ couplings could result in an enhanced rate of W pair production. Standard Model WW production is also an important background for a heavy Higgs signal :

wwu

where the ggH vertex is via a quark loop, and is also a background to t-tbar production, and searches for new heavy gauge bosons.

Summary of Results
We find 17 dilepton candidate events compared to an expected background of 5.0(+2.2)(-0.8) events in a Run 2 data sample with a luminosity for WW events of approximately 184/pb. This results in a measured cross-section of:

dphi_met_lep

which is in agreement with a NLO (Next-to-Leading-Order) theoretical prediction of 12.4 ± 0.8 pb.

Summary of Event selection

Lepton Selection

electrons can be:
- Central(CEM): Et > 20 GeV and |eta|<1.1
- Forward(PHX): Et > 20 GeV and 1.1<|eta|<2.0
muons can be:
- Triggerable: Pt > 20 GeV, |eta|<1.0, fiducial in muon chambers
- Non-Triggerable: Pt > 20 GeV, |eta|<1.2, not fiducial in muon chambers

Event selection

Two high-Pt leptons, both isolated
If both leptons are same flavour, require 76<M<106, and no significant Missing Energy
Missing Et (MET) > 25 GeV
Delta-phi (MET, nearest lepton) > 0.35 if MET < 50 GeV
No jets with Et > 15 GeV (corrected), and |eta| < 2.5
Both leptons of opposite charge

Summary of Backgrounds, Expected Signal, and Data
dphi_met_lep

All channels combined; comparing this analysis with a "Lepton Plus Track" cross-check analysis :
dphi_met_lep

Kinematic Distributions

eps	eps	eps
eps	eps

Event Displays

e-e WW candidate	e-&mu WW candidate	&mu &mu WW candidate
eps	eps	eps

Last Updated February 9, 2005 (DSW)