1. Investigation on Diboson Production
Ye Li
Graduate Student
UW - Madison

2. Diboson physics at tevatron
Provide a stringent test for SM TGC (Trilinear Gauge Coupling)
TGC is sensitive to NP (New Physics)
Involve 5 C- and P-conserving coupling parameters
Probe the deviation of some parameters
Effective Lagrangian (SM: g =κ= 1, λ= 0)
V = Z, γ

3. Wγ production Test of WWγ TGC
Anomalous Coupling leads to and enhancement of the Cross Section and an excess of High Energy Photon
Identify W by leptonic decay (W →lν )
Dominant background: jet mimics isolated Photon
Separation Requirement: Δ R > 0.7

4. Result Luminosity: 200 pb-1 (CDF) and 162 pb-1 (DO)
Wγ Cross Section × BR (Leptonic decay of W):
CDF: 18.1 ± 1.6(stat) ± 2.4(syst.) ± 1.2(lum.) pb; NLO expectation: 19.3 ± 1.4 pb)
DO: 14.8 ± 1.6(stat) ± 1.0(syst.) ± 1.0(lum.) pb; CDF NLO expectation: 16.0 ± 0.4 pb)
Consistent with SM; Not evident for NP

5. Zγ production Combination of ZZγ and Zγγ TGC
Identify Z by leptonic decay (W →l l )
Dominant background: jet mimics isolated Photon (the same as Wγ)
Separation Requirement: Δ R > 0.7

6. Result Luminosity: 200 pb-1 (CDF) and 300 pb-1 (DO)
Zγ Cross Section × BR (Leptonic decay of Z):
CDF: 4.6 ± 0.5(stat) ± 0.2(syst.) ± 0.3(lum.) pb; NLO expectation: 4.5 ± 0.3 pb)
DO: 4.2 ± 0.4(stat + syst.) ± 0.3(lum.) pb; CDF NLO expectation: 3.9 ± 0.2 pb)
Still Consistent with SM

7. WW production WW final state: a promising channel for Higgs boson
WWγ and WWZ coupling involved
Higher invariant mass probed in CDF compared to LEP
Signature: leptonic decay of W
Contamination: t t-bar events
Dominant Background after Selection Cut: Drell-Yan, other diboson decay and Jet faking isolated lepton

8. Result
Luminosity: 240 pb-1 (DO published) and 825 pb-1 (CDF preliminary)
σ (p p-bar → WW + X):
DO published: (stat) (syst.) ± 0.9(lum.) pb
CDF preliminary: 13.6 ± 2.3(stat) ± 1.6(syst.) ± 1.2(lum.) pb
NLO expectation: 12.4 ± 0.8 pb)
Also Consistent with SM

10. WZ / ZZ production WWZ TGC, WWγ not involved here
Sum of WZ and ZZ production (p p-bar → WZ + ZZ) searched in 2, 3 and 4 lepton channels
Direct search of WZ production in trilepton + MET channel
Dominant background in WZ direct search: Z + X where X = Z, γor jet faking a lepton

11. Result σ (p p-bar → WZ + ZZ) Luminosity: 194 pb-1
SM expectation: 5.0 ± 0.4 pb
Measurement: (stat)± 0.4 (syst.) pb
CDF: σ < % CL

12. Result NLO σ(p p-bar→WZ) = 3.7±0.3pb (CDF) DO published
Luminosity: 300 pb-1
< % CL
(stat + syst.)
CDF preliminary
Luminosity: 825 pb-1
< % CL

14. WW + WZ in lνjj Search in channel lνjj
Advantage than pure lepton channel: larger branching fraction
The result shows no statistically significant evidence for this event
σ(p p-bar → WW + WZ) < 36 95% CL

15. Summary No deviation from the Standard Model is observed
More stringent search in NP by the end of Run II