Search for W(lv)W/Z(jet-jet) at sqrt(s)=1.96 TeV

Contact: Jorgen Sjolin, sjolin at fnal dot gov.

Abstract

We have performed a search for the semi-leptonic diboson channel W(lv)W/Z(jet-jet) using 350/pb of data taken at 1.96 TeV ppbar center-of-mass energy. Central electrons and muons from the leptonic decay of the W are used for the event trigger and the shape of dijet mass spectrum is used to discriminate the hadronic W/Z(jet-jet) decay from the QCD background. Note that the W(jet-jet) decay cannot be separated from Z(jet-jet) due to the limited jet resolution, hence both channels are included as part of the signal.

The semi-leptonic diboson process is still not observed at hadron colliders. Compared to the pure WW leptonic diboson decay the semi-leptonic process is interesting due to its higher event yield and its ability to provide a direct handle on the boson transverse momentum (pt). The sensitivity to very high boson pt makes this process particularly useful as a probe of the gauge structure (symmetries) at high energies where we at some point anticipate new physics.


Event selection criteria
 Value
1 central electron Et (muon Pt)
 > 25 (20) GeV
Missing Et
 > 25 GeV
Z and cosmics veto
 Yes
2 or more jets Et (hadronic scale)
 > 15 GeV (20 GeV a.c. analysis)
dR(lepton,jet)
 > 0.5
dR(jet,jet)
 > 0.5
dPhi(jet,MET)
 > 0.2
dPhi(lepton,MET)
 > 0.3
Transverse momentum (lepton,MET) (anomalous coupling analysis)
 > 20 GeV
Transverse mass (lepton,MET)
 > 25 GeV
Dijet mass (cross-section analysis)
 32 GeV < mjj < 184 GeV
Dijet mass (anomalous couplings analysis)
 56 GeV < mjj < 112 GeV


Background processes (cross-section analysis)
 Data fit
 Uncertainty
 Expected event yield
W + jets
 Floating
 20%
 6261
Non-W background
 Fixed
 40%
 263.4
W(tau) + jets
 Fixed
 20%
 171.0
Z + jets
 Fixed
 20%
 154.0
tt
 Fixed
 25%
 171.6
t(t-ch)
 Fixed
 25%
 14.4
t(s-ch)
 Fixed
 25%
 8.2


Source (cross-section analysis) Signal uncertainty
Data statistics
 69%
Jet energy scale
 16%
Non-W
 16%
QCD renomalization scale
 8%
Jet resolution
 19%
ISR/FSR
 10%
Signal dijet shape shape
 10%
Luminosity
 6%
Leptonic W
 3%
Total
 69% (stat), 34% (sys)


Signal processes
 Data fit
 Uncertainty
 Event yield
W W
 Floating
 15%
 142.0
WZ
 Floating
 15%
 18.2
Data (WW+WZ) fit
69%(stat), 34%(sys)
 109


Signal processes Cross-section limit, 95% CL, FC stat. (pb)
W W+WZ
 < 36


Anomalous couplings limits, 1D,  95% CL
(Equal TGC for Z and gamma, Lamda=1.5 TeV)
-0.51 < Δ κ < 0.44
-0.28 < λ < 0.28


Plot Sideband region
 Signal region
MC signal dijet mass
 MC dijet mass shape
gif | eps
MC dijet mass total stacked MC dijet mass total stacked
gif | eps
Dijet mass (cross-section analysis)
 Signal and background hypothesis fit to data
gif | eps
Dijet mass (anomalous couplings analysis)
 Signal and background hypothesis fit to data
gif | eps
Lepton pt
Lepton pt (signal region)
gif | eps
MET
MET (signal region)
gif | eps
W transverse mass
W transverse mass (signal region)
gif | eps
Leading jet pt
Leading jet pt (signal region)
gif | eps
Second jet pt
Second jet pt (signal region)
gif | eps
Delta R
Delta R (signal region)
gif | eps
Cluster transverse mass (stacked)
CTM (signal region)
gif | eps
W pt (stacked)
W pt (signal region)
gif | eps
Cluster transverse mass (systematic band)
 CTM (sideband region)
gif | eps		 CTM (sideband region)
gif | eps
W pt (systematic band)
 W pt (sideband region)
gif | eps		 W pt (signal region)
gif | eps
Background systematics (anomalous couplings)
Background systematics
gif | eps
Signal systematics (anomalous couplings)
Background systematics
gif | eps
Limits on anomalous couplings
Limits anomalous coupoling
gif | eps