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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Top Physics and

SM Higgs Searches at the Tevatron

Outline:

•The Tevatron Upgrade

•CDF and DØ Detectors

•Top Physics:

•Cross Section Production

•Top Mass

•SM Higgs searches

Antonio Sidoti

University of Pisa and INFN XV IFAE Lecce 2003

24 Aprile 2003

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

CDF DØ

Main Injector Tevatron Booster

Recycler

Fermilab Tevatron Upgrade (RunII)

Not used yet!

Lum at RunI ~110 pb -1

√ s RunI = 1.8 TeV Now √s RunII = 1.96 TeV

Higher Luminosity for RunII

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

0.00E+00 1.00E+31 2.00E+31 3.00E+31 4.00E+31 5.00E+31

04/01/01 05/01/01 06/01/01 07/01/01 08/01/01 09/01/01 10/01/01 11/01/01 12/01/01 01/01/02 02/01/02 03/01/02 04/01/02 05/01/02 06/01/02 07/01/02 08/01/02 09/01/02 10/01/02 11/01/02 12/01/02 01/01/03 02/01/03 03/01/03

Date

Peak Luminosity

0.00E+00 1.00E+31 2.00E+31 3.00E+31 4.00E+31 5.00E+31

Peak Lum 20x Average

Peak Luminosity Peak Lum 20X Average

Peak Luminosity

Winter 03 Data

RunIIa Tevatron Performances

– Base goals:

¾200 pb

-1

for 2003

¾10 pb

-1

/week by the end of the year

– Stretch goals:

¾320 pb

-1

for 2003

¾15 pb

-1

/week by the end of the year

– 2002 comparison:

¾ 80 pb

-1

for the year

¾ 6.7 pb

-1

best week

0.00 1000.00 2000.00 3000.00 4000.00 5000.00 6000.00 7000.00 8000.00

1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96 101

Week # Weekly Integrated Luminosity (nb-1)

0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 180.00 200.00

Run Integrated Luminosity (pb-1)

Weekly Integrated Luminosity Run Integrated Luminosity

Integrated Luminosity

Winter 03 Data

10

31

Bunch Crossing Interval:

τ RunI = 3.5 µs

τ Run II= 396/132 ns

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

DØ RunII Detector

Many improvements from RunI:

•New solenoid installed for

•RunII (2T 60cmx2.8m ) ->New Tracking system

•Trigger + Electronics and DAQ

Si Tracker: Layers&Disks

8 Layers Fiber Tracker

Preshower

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

CDF RunII Detector

From RunI:

•Solenoid

•Muon system

•Central Calorimeter

For RunII:

•Front-end DAQ

•Trigger

Track (L1) and Displaced Track (L2)

•New Silicon Tracker (8 Layers) (|η|<2)

•Central Outer Tracker

•TOF •Plug Calorimeters

•Extended Muon Coverage (eµ) Id up to |η|~2

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

¾ Today results only RunII although integrated luminosity ~60% of RunI

¾ Re-establish Run I results

Î Proof that RunII Detectors are working well!

¾ More statistics ÖStudy Top properties with more precision (charge,BR, rare decays,...)

¾ Search for new phenomena ( e.g. single top searches, SM Higgs searches, etc…)

Top Physics at the Tevatron (backup)

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Tevatron RunI Results

ttbar production cross

section M W vs M top -> Higgs Mass

Luminosity ~110 pb -1 s = 1.8 TeV

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Run I Top Mass (backup)

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

At the Tevatron, top quarks are primarily produced in pairs

mainly from qqbar Top decays as free quark BR(t

Æ

Wb) @ 100 %

3 classes of signal

Dilepton: Clean but small statistics: BR 5%

Lepton + jets: Larger statistics Higher background:

BR 30%

All-hadronic: Higher statistics Huge background: BR 44%

Branching ratios for tt decay modes

Production and decay of Top quark

e-e(1/81) mu-mu (1/81) tau-tau (1/81) e -mu (2/81) e -tau(2/81) mu-tau (2/81) e+jets (12/81) mu+jets(12/81) tau+jets(12/81) jets (36/81)

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Data

0.07±0.04 0.09±0.05 0.04±0.03 0.10 ±0.07

5

0.30±0.12 Background

2.5±0.03

Expected (σ=7pb)‡

Z →ττ WW/WZ QCD DY

CDF:Dilepton Channel

• Event selection

– 2 High P

T

(P

T

>20 GeV) oppositely charged leptons (ee,µµ,µe) |η|<1.

– Both isolated: I

CAL

< 0.1 – Large missing E

T

> 25 GeV

– at least 2 jets with E

T

> 10 GeV – Total transverse energy of the

event (H

T

)> 200 GeV

– Veto Z’s, cosmics, and conversions

•BR~5%, detection eff ~ 11%, expect S/B~9, S~2.5

•5 candidate events in 72 pb

-1

‡ σ

tt

(@ √s = 1.96 TeV and M

top

=175 GeV/c

2

) = 6.70

+0.71-0.88

pb From Cacciari et al (hep-ph/0303085)

fro m da ta

fro m M C

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Met : Dilepton Events

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

σ tt = 13.2 ± 5.9 stat ± 1.5 syst pb

NLO for M

NLO for M

top top

= 175 = 175 GeV GeV : 6.70 : 6.70

+0.71+0.71-0.88-0.88

pb pb

CDF:Dilepton cross section (ee,µµ,eµ)

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Dilepton e-µ

Run/Event 155114/478702

muon

electron

electron

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

• Event selection

– 1 High momentum,

central(|η|<1), and isolated lepton

– P

T

>20 GeV/c, e or µ.

– Large missing E

T

> 20 GeV – 3 or more jets with E

T

> 15

GeV

– Veto Z’s, cosmics, and conversions

– at least 1 jet with secondary vertex tag (SVX)

• 15 observed events in 57.5 pb

-1

• Backgrounds from

Wbb,Wcc,mistags,Wc, non-W (Data and MC): 3.8 ± 0.5

CDF: Lepton+Jets

signal

control

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

W+jet Background composition

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

CDF: b-tagging from Secondary Vertex

Kinematical distributions for b-jets MC data

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

µ +4jets(+2 SVX tag)

Run/Event 153693/799494

MET 40.2 GeV

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

CDF: tt cross section measurement

Dilepton

Theory (NLO)

Mtop=175 GeV/c2

√s=1.96 TeV

6.7 +0.71

-0.88

13.2 ± 5.9 stat ± 1.5 syst 5.3 ± 1.9 stat ± 0.8 syst Lept+Jet

CDF σ ttbar (pb) @ √ s=1.96 TeV

Run II (Lept+Jet) Run I CDF

combined

From Cacciari et al (hep-ph/0303085)

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Luminosity:

Selection Criteria: 42.6 pb -1 (µµ)

2 Isolated muons, MET,H T and more than 2 jets

Data Signal (MC)

WW (MC) Z-> µµ

DØ:Dimuon channel

Data 2

0.60±0.30 Background

0.3±0.04 Signal (σ=7pb)

0.20±0.11 0.20±0.20 0.18±0.18 0.02±0.02 0.00±0.00 Z →µµ

DY →µµ QCD Z →ττ WW

From Data From MC

x

x

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Luminosity:

Selection Criteria: 33.0 pb -1

1 electron, 1 isolated muon, H T (e) and more than 2 jets

H

T

(e) (GeV) N

jets

Z →ττ Z

Fakes Fakes

Data 1

0.07±0.01 Background

0.5±0.01 Signal (σ=7pb)

0.05±0.01 0.02±0.02 0.00±0.00 QCD Fakes

Z →ττ WW

DØ: Dilepton (eµ)

From Data

From MC

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Luminosity: e+jets 49.5pb -1 µ +jets 40.0pb -1 Preselection:

lepton with Pt>20 GeV/c MeT>20 GeV

Njet>=4

veto non-isolated soft muon

Evaluate W+4 jet scaling from W+n jets

Topological Selection

W

|<2.5 and E

T

(W)>60 GeV H

T

>220 GeV

Aplanarity>0.065

DØ: Lepton+Jet

α = 0.145±0.02 α = 0.164±0.02

) (

) ) 1 (

(

jets jets

n W

n W

+ +

≡ +

σ α σ

Behrends scaling:

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

µ -

MTC

Jet 3 Jet 1

Jet 2

Jet 4 Jet 5

µ +jet Candidate event

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Preselection: Topological + Aplanarity>0.04

3 jets with Et>20 GeV and |η|<2 H

T

>110 GeV

Soft Muon Tag:

Pt(µ)<4 GeV/c

∆ R<0.5

Strategy: Use semileptonic b decay to identify b-jet

DØ:Lepton+Jet (Soft Muon Tag)

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

DØ:Cross Section Measurement

pb (lumi) 0.8

(syst)

(stat) 8.4

σ =

+4.53.7 +5.33.5

±

Combining measurements

from the different decay

channels

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

METHOD

Use 2C constrained fitting technique with constraints M

ιν

= M

W

, M

jj

=M

W

, M

t1

=M

t2

24 combinations:

12 correspond to the jet parton match

every combination has 2 solutions for neutrino P

Z

Choose combination with lowest χ

2

.

l ν

W +

W - t t

b-jet

b-jet

jet jet

X

Select lepton + 4 jet events, similar to the σ(tt)

lepton+jet measurement, except no requirement on silicon.

CDF: Top Mass

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Reconstructed top masses from data are compared to parameterized templates of top and background Monte Carlo.

signal

background

CDF:Top Mass

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Use a continuous likelihood method to extract top mass and

statistical uncertainty

CDF: Top Mass

RunI Uncertainty was 4.4 !

We know how to improve it!

M

Top Run(II)

=171.2±13.4±9.9 GeV/c

2

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Top Mass: b-tag

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

M Top : Run II Perspectives

Full Run IIa Luminosity: 2 fb

-1

Larger statistics for the signal sample

Larger number of control

sample Î Smaller systematics

Run II expectations in 2 fb

-1

Channel

Dilepton (e,m) Dilepton t

Lepton+3 jet/+1 btag Lepton +4 jet/+2 btag

155 19 1520/990 1200/240

∆ M top ~3 GeV/c 2

Run IIa

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Tevatron may play a role with low mass range M H .

•gg->H

•Huge background for

H->bb (may be H->ττ/WW)

•Associated Production (HW/HZ) with H->bb

Most promising channel!

•qqHqq and ggHQQ Overwhelmed by background

SM Higgs Production and Decay

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

SM Higgs: Run I and Run II

Run I W/Z H and H->bb

Direct searches:

factor 30 below SM!

RunII Combined Higgs Sensitivity

Subject to a critical re-evaluation based on RunII experience.

LEP excluded at 95% C.L.

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

W/Z+jets production:DØ

•Key for W/Z associated production

•Select a clean sample of W/Z + jets (using leptons)

•Understand background, tune MC, etc...

2

nd

leading jets 1

st

leading jets

GeV QCD BKG

QCD BKG

Dot : Data Bar : MC

GeV

Di-jet Mass W(eν)+jets

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Z+jets production:DØ

Combined Z(ee)+jets and Z(µµ)+jets

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Tools for Higgs Searches

Combine CDF and DØ results: Advanced Statistical Tools B-tagging: (cf. CDF:Lepton+Jet)

Jet corrections: Improve M

bb

resolution with specific corrections Z->bb

(Data RunI) Specific b-jet

corrections

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Perspectives

Tevatron

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A. Sidoti INFN Pisa and University

IFAE Lecce 2003

Perspectives and Conclusion

¾ Run I results re-established ÎBoth detectors are working well !

¾ But don’t just wait for more luminosity..,

¾ Now we will pursue “new” strategies

¾ Expanding detectors capability to their full acceptance

¾ Search for new phenomena ( e.g. single top searches, Rare decays, SM Higgs searches, …)

Conclusions

Riferimenti

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