Di-boson Physics at the TeVatronAndrew Alton

University of Michigan

CDF

Outline Introduction Measurement of W cross section Measurement of Z cross section Measurement of WW cross section WZ(ZZ) cross section limits

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Diboson Production

SU(2)LxU(1)Y Electroweak sector non-Abelian theory including boson couplings WW, WWZ (Trilinear gauge boson vertices)

Events with two bosons are sensitive to trilinear gauge boson vertices.

The standard model (SM) has very specific (and small) predictions for the cross section of Di-boson events.

Extensions to the SM often enhance these cross sections. Especially for high boson pt.

Places limits on Anomalous Trilinear Couplings

These final states are backgrounds for other important physics (H->WW, tt->dilepton,etc)

W W

W W

Z Z

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Object Identification

Electrons EM cluster in Cal Et >15 GeV

(often higher 20,25) Track match Shower shape/likelihood CDF - |e| < 1.1, 1.2<|e| <

2.6(2.0) D0 - |e| < 1.1, 1.5<|e| < 2.5

Muons Muon chamber hits Central Track assoc. PT > 20 GeV(15 in Z)

CDF - || < 1.0

D0 - || < 2.0(1.6)

Photons EM cluster in Cal Et >7(8) GeV

CDF(D0) Track veto and isolation Shower shape || < 1.1

Isolated Track Missing Et.

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W Production

W also has an interesting feature interference creates a zero

amplitude in the charge signed rapidity difference between the l and .

Monte Carlo

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W Cross Section

Electron(Muon) Electron(Muon)

Lumi (pb-1) 202(192) 162(82)

ET > 7 GeV > 8 GeV

Tot Bkg 94.7 ± 23.6 124.1 ± 12.5

Candidates 323 223

(pb) 19.7±2.8(stat+sys)±1.1(lum) 19.3±6.7(stat+sys)±1.2(lum)

NLO Theory 19.3 ± 1.4 16.4 ± 0.4

CDF

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Photon Et

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Z Cross Section

Electron(Muon) Electron(Muon)

Lumi (pb-1) 202(192) 177(144)

ET > 7 GeV > 8 GeV

Tot Bkg 4.5 ± 0.8 14.8 ± 1.5

Candidates 70 101

(pb) 5.3±0.7(stat+sys)±0.3(lum) 3.9±0.5(stat+sys)±0.3(lum)

NLO Theory 5.4 ± 0.4 4.3

CDF

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Photon Et

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Two body vs Three Body Mass

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WW Cross Section

Chan ee e All ee e AllBkgd 1.97

0.401.14 0.28

1.66 0.31

4.77 0.70

2.30 0.26

1.94 0.43

3.81 0.30

8.05 0.7

Exp. Sign. *

2.90 0.34

2.75 0.32

5.69 0.66

11.3 1.3

3.26 0.05

2.01 0.05

10.8 0.1

16.1 0.10

Candidates

6 6 5 17 6 4 15 25

CDF

(pp->WW) = 14.3 +5.6 –4.9(Stat) 1.6(sys) 0.9(lum) CDF (lep+trk) = 19.4 5.1(stat) 3.5(sys) 1.2(lum) CDF (dilepton) = 13.8 +4.3 –3.8(Stat) 1.0(sys) 0.9(lum) D0 * CDF uses 13.3 0.8 while

D0 assumes 13.0

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WZ to tri-leptons

D0 looks for W/Z to 3 leptons(e and ). Expects 0.39 0.02 background events Expects 1.02 0.07 signal events (assuming 3.7 pb) Find 1 candidate event. Set upper limit on cross section of 15.1 pb

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Candidate Event

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WZ and ZZ Production

CDF looks for a WZ and ZZ candidates by requiring a Z(ee or ) and Met Significance (sensitive to Z-> and WZ) Or third lepton & MET Or four leptons.

Expect 2.72+-0.33 of signal And 2.29+-0.42 of background Find 4 candidates (all 2 track) Set a limit (ZZ+ZW)<13.9 pb Theory is (ZZ+ZW)=5.2+-0.4 pb

CDF

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Conclusions

Both Tevatron experiments are doing well.

Collection of preliminary cross sections:

Expect limits on anomalous couplings

Analysis using hadron final states underway.

Expect final results and publications soon.