First Evidence of WW/WZ ---> l nu qq at the Tevatron Page: 2 of 7
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if < 2 (for muons), an imbalance in transverse momentum $T> 20 GeV, and at least two jets 7
with pT > 20 GeV and 'if < 2.5. The leading jet (i.e. with the highest pT) was also required
to have pT > 30 GeV. To reduce background from processes that do not contain W -> Ev, we
required a transverse W mass of M7 > 35 GeV, where MT (ET)2 - (pT28. The electron
or muon trajectories were required to be isolated from other objects in the calorimeter, and had
to match a track reconstructed in the central tracking system that originated from the primary
vertex. Also, the muon had to be reconstructed as an isolated track in the central tracking
system. The resulting kinematic distributions are shown in Fig. 1.
y 4300 DO, 1 1 +1 +Data
O 4000 -Diboson Signal
00 20 40 60 80 100 120 140
Lepton pT (GeV)
L5000 DO, 1 1 th'
3000 _ op
0 20 40 60 80 100 120 140 160 180 200
Leading Jet pT (GeV)
DO, 1 1 +1 +Da
20 40 60 80 100
DO, 1 1 thb'
-0 20 40 60 80 100 120 140
Second Leading Jet pT (GeV)
1 1 tb
00 20 40 60 80 100 120 140 160 180 200
Transverse W Mass (GeV)
3500 DO, 1 1 fb-- +Data
3000 -Diboson Signal
c 2500 -Z+jets
0 50 100 150 200 250 300
Dijet Mass (GeV)
Figure 1: Kinematic distributions after all selection requirement: (a) pT of lepton; (b) $qT; (c) transverse W mass;
(d) pT of leading jet; (e) pT of second-leading jet; (f) dijet mass.
3 Data Sample
The data were collected with the DO detector 5 at the Fermilab Tevatron Collider at a center-
of-mass energy of f/ = 1.96 TeV. The events studied in this analysis correspond to 1.07 fb-I
of integrated luminosity collected during Run IIa (2002-2006). To be considered for analysis,
events in the evqq channel were required to pass at least one single electron or electron+jet(s)
trigger. The resulting trigger efficiency was 98+3%. A suite of triggers was used for the pvq
channel resulting in a trigger efficiency of nearly 100%.
4 Signal and Background Estimations
Monte Carlo generators were used to simulate the signal and background samples that contained
a charged lepton in the final state. Signal events were generated with PYTHIA 9 using CTEQ6L
parton distribution functions (PDF). ALPGEN 1o with CTEQ6L1 PDFs was used to generate
W+jets, Z+jets, and tt events and COMPHEP II with CTEQ6L1 PDFs was used to simulate
single-top events. All ALPGEN and COMPHEP events used PYTHIA for parton showering and
hadronization. After generation, the events underwent a GEANT-based 12 detector simulation
before being reconstructed with the same programs as the data.
With the exception of W+jets, all background MC samples were normalized to next-to-
leading-order (NLO) or next-to-next-to-leading-order SM predictions. The W+jets normaliza-
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Haley, Joseph & U., /Princeton. First Evidence of WW/WZ ---> l nu qq at the Tevatron, article, July 1, 2009; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc928134/m1/2/: accessed August 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.