1. Generator Study of W(mn)g @ Tevatron collider

2. 2 vs. 3 body W(mn)gamma and CSRD
Motivation: precise test of RAZ of SM, and probe ATGC in both photon pT and RAZ
Both call for on-shell W, cascade decaying leptonically, i.e. 22 2body final states. This is what Pythia does;
but experimentally, what observed in m+n+g, and under on-shell W assumption predicted by Pythia
Radiation Amplitude Zero (RAZ)
Charge Signed Lepton Photon Rapidity
Difference (CSRD) in Tevatron Lab frame
in Wg rest frame
Blue stands for Pythia in all slides

3. Distort of CSRD and dphi
The correct treatment of m+n+g 3-body final states, including lepton FSR and interference, as CompHep (here I assume Baur-LO gives the same results as CompHep)
On-shell W Events by Pythia8
FSR-inclusive Events by Comphep
Significant difference of 2- and 3-body treatment
M(mn)
CSRD
off-shell effects in 23
Distort of CSRD and dphi
M(mng)
dphi(mg)

4. Photon PT >10, Muon PT > 20, Neutrino PT > 20,
Kinematic cuts to “restore” Pythia?
Photon PT >10, Muon PT > 20, Neutrino PT > 20,
dR > 0.7, MT(lng)>110GeV
W- Events by Pythia8
W- Events by Comphep
Photon pT
Muon pT
Neutrino pT
dR(mg)

5. Photon PT >10, Muon PT > 20, Neutrino PT > 20,
dR > 0.7, MT >110GeV
W- Events by Pythia8
W- Events by Comphep
M(mn)
M(mng)
MT(mng)

6. Photon PT >10, Muon PT > 20, Neutrino PT > 20,
dR > 0.7, MT >110GeV
W- Events by Pythia8
W- Events by Comphep
Photon eta
Muon eta
dphi(mg)
CSRD
This CSRD plot is in consistent with previous result, where a plain instead of peak in the right was seen, see next slide

7. Charge Signed Lepton Photon Rapidity Difference
Plots of Different Cut
On-shell W Events
MT3 >110GeV Events
MT3 >100GeV Events
MT3 >90GeV Events
Photon PT >10GeV
Lepton PT >20GeV
Missing ET >20GeV
dR>0.7
Charge Signed Lepton Photon Rapidity Difference

8. Conclusion 1
+ 3-body FRS and interference differs from on-shell Wgamma production and lepton decay
+ Cuts as MT>110GeV will suppress off-shell effect, and give good photon pT agreement,
but dphi and CSRD of lepton and photon
+ Question: we see dphi and CSRD difference of Wgamma-LO and Pythia, how can we trust a
2-body NLO QCD Wgamma-NLO?

9. Parameters used in Comphep vs. WGAMMA
3 body consistency: CompHep vs BaurLO
Parameters used in Comphep vs. WGAMMA
Beam type
ppbar
Energy (TeV)
1.96
PDF
CTEQ6L
αem
1/132.43
M(W)
80.41
M(Z)
91.188
sin2θw Гw
2.103

10. Photon PT >5GeV, dR(l,γ) > 0.7
W- Events by Comphep
W- Events by WGAMMA
Photon PT >5GeV, dR(l,γ) > 0.7
Photon Pt
Muon Pt
Neutrino Pt
dR(muon,photon)

11. Photon PT >5GeV, dR(l,γ) > 0.7
W- Events by Comphep
W- Events by WGAMMA
M(mn)
M(mng)
MT(mng)

12. Photon PT >5GeV, dR(l,γ) > 0.7
W- Events by Comphep
W- Events by WGAMMA
Photon Eta
Muon Eta
Dphi(mg)
CSRD