Results for Top and Higgs at Tevatron

CDF

ICHEP 2004, August 16-22, Beijing ChinaDmitri Denisov, Fermilab

Results for Top and Higgs at TevatronResults for Top and Higgs at Tevatron

Tevatron

CDF and DØØ

Top quark studies

Search for Higgs

Summary

Outline

Dmitri Denisov, ICHEP04, August 21 2004 2

CDFTop Quark Studies and Higgs Top Quark Studies and Higgs

SearchesSearchesDiscovery of top quark at Fermilab in 1995

Completed SM Quark SectorStudies of heaviest known elementary particle

SM parameters, testsBeyond SM searches

Higgs boson is last missing particle in SMDescribes EWSM – particle

massesExperimental challenges: low cross sections and substantial backgrounds

AcceleratorDetectorsAnalysis

Tevatron currently is the only accelerator able to produce such heavy particles


CDF Tevatron ParametersTevatron Parameters

82.32.5Interactions/ crossing

3963963500Bunch crossing (ns)

50173 Ldt (pb-1/week)

3 10329 10311.6 1030Typical L (cm-2s-1)

1.961.961.8s (TeV)

36 3636 366 6Bunches in Turn

Run IIbRun IIaRun I

Run I Run IIa Run IIb 0.1 fb-1

Substantial upgrades for Run II: 2001-2009

10% energy increase: 30% higher top

integrated luminosity increase: x50

6 km long Tevatron ring


CDF Tevatron Run II PerformanceTevatron Run II Performance

Peak luminosity is above 1.1032 cm-

2sec-1

Reliable operation in stores ~120

hours/week

Total ~0.7 fb-1 delivered in Run II as planned

1.1032 cm-2sec-1

1 week=168 hours

0.7 fb-1


CDFTevatron Long Term Luminosity PlanTevatron Long Term Luminosity Plan

To reach higher masses with the same energy

higher luminosity

Increase in number of antiprotons the key for higher

luminosity

Expected peak luminosity 3.1032 cm-2sec-1 by 2007

Currently expecting delivered luminosity to each experiment

4-8 fb-1

by the end of 2009

Today


CDFCDF and CDF and DDØØ Experiments in Experiments in

Run IIRun II

New Silicon DetectorNew Central Drift ChamberNew End Plug CalorimetryExtended muon coverageNew electronics

Silicon Detector2 T solenoid and central fiber trackerSubstantially upgraded muon systemNew electronics

Driven by physics goals detectors are becoming “similar”: silicon, central magnetic field, hermetic calorimetry and muon systems

CDF DØØ


CDFData Collection by Data Collection by

ExperimentsExperiments

CDF

CDF and D0 experiments are very complex

Typical ratio of “recorded” to “delivered”luminosity is 80%-90%

As of now both experiments recorded ~0.5 fb-1

Results presented correspond to ~0.2 fb-1

Analyzed data

Analyzed data


CDF Detection of High PDetection of High Ptt Objects Objects

Electrons

Missing Et

Muons

Jets

D0 PreliminaryTop and Higgs final

decay products electrons

muons jets (b)

missing Et ()Detection and MC

optimization using well known objects

b tagging


CDF Top Quark StudiesTop Quark Studies

Heaviest known elementary particle: 180GeV

measure properties of least known quark

top quark mass constrains Higgs mass

sensitive to new physics

short life time: probe bare quark


CDFTop Quark Production and Top Quark Production and

DecaysDecays

Top quarks at Tevatron are (mainly) produced in pairs via strong interaction

Top pair cross section at 1.96 TeV is 6.7 pb

In SM top decays 100% to WbClassification of top decays

is based on Ws decays

% e qq

e 1.2 2.5 2.5 14.8

1.2 2.5 14.8

1.2 14.8

qq 44.4

Top decays classification: di-lepton, lepton+jets, all jets

Production Decay

85%

15%


CDF Selection of Top Quark EventsSelection of Top Quark Events

In triggering and analysis select events with high Pt leptons high Et multiple jets large missing Et () displaced vertex for b jets

“Di-lepton” mode has low backgrounds: di-bosons, Drell-Yan, ... but low statistics: ~5% for e, decays“Lepton+jets” very productive mode 6 times more decays then di-lepton mode main background W+jets good purity after b tagging“All jets” mode ~50% branching high QCD backgrounds, jets combinatoric


CDFDDØØ Top Cross Section in di-lepton Top Cross Section in di-lepton

ChannelChannel

Topological selection isolated (not in jet) high Pt ee(156 pb-1), (140 pb-1), e(143 pb-1) pair 2 or more jets large missing Et

Backgrounds: WW, Z+jets, W+jets, fakes

Extra b tag

Ultra-pure sample of top events: S/N>50

e only

D0 Run II Preliminary pb)()(3.14)( 6.2

9.11.53.4 syststattt

pb)()(1.11)( 4.14.1

8.53.4 syststattt

Cross Section


CDFCDF Top Cross Section in di-lepton CDF Top Cross Section in di-lepton

ChannelChannel

197 pb-1 data sample for all channels topological selection

Combine ee, and e channels for best precision

pb


CDFCDF Top Cross Section in lepton+jets CDF Top Cross Section in lepton+jets

ChannelChannell+jets with vertex b tagging

l+jets with soft lepton tagging

l+jets topological

pb)()(2.4)( 4.14.1

9.29.1 syststattt

Exploit different strategies higher statistics – topological b-jets tagging displaced vertex soft lepton ()

pb)()(6.5)( 0.17.0

2.10.1 syststattt

pb)()(7.6)( 6.16.1

1.11.1 syststattt


CDFDDØØ Top Cross Section in lepton+jets Top Cross Section in lepton+jets

ChannelChannel

Selection of events (topological method) high Pt lepton large missing Et

4 or more jets (no b tagging)

Form topological discriminant to optimize top events selection

Single b tag Double b tag

Tagging jets from b decays using displaced vertex algorithms

reduces backgrounds substantially

pb)()(2.8)( 9.16.1

3.13.1 syststattt

pb)()(2.7)( 6.17.1

6.24.2 syststattt


CDFRun II Top Quark Cross Section: Run II Top Quark Cross Section:

SummarySummary

Measurements demonstrate success of multiple top detection techniquesResults within errors consistent with NNLO SM predictions for 1.96TeV of 6.7pb

Errors between different channels are correlated


CDF Top Quark Mass MeasurementTop Quark Mass Measurement

Fundamental SM parameterTop mass together with EW data constrain Higgs mass

Using Run I l+jets events (125 pb-1) DØØ developed “matrix element method”

Detailed knowledge of top quark decay and detector response is required event by event likelihood calculated vs mt

mt = 180.13.6(stat)3.9(syst) GeV

PDFsPhase space x LO ME Probability for observable x when y was produced (Ex: quark ET jet ET)

Currently single most precise top mass measurement


CDF Run II Top Mass Measurement at CDFRun II Top Mass Measurement at CDFRun I style “template” method is efficiently used

di-leptons l+jets, b tagged l+jets, multivariate

Dynamical Likelihood Method is similar to D0 “matrix element method”

GeV )(2.6)(8.177 5.40.5 syststatmt

Single most precise Run II measurement

GeV )(9.6)(5.176 2.170.16 syststatmt

GeV )(5.6)(9.174 1.77.7 syststatmt

GeV )(8.6)(6.179 4.63.6 syststatmt


CDFTop Quark Mass Measurement at DTop Quark Mass Measurement at DØØ in in

Run IIRun IIMeasurements in l+jets channel (~150 pb-1)

template method uses templates for signal and background mass spectra ideogram method uses analytical likelihood for event to be signal or background

Template method mt = 1706.5(stat)+10.2/-5.7(syst) GeV

Ideogram method mt = 177.55.8(stat)7.1(syst) GeV

Template

Ideogram


CDFTevatron Top Quark Mass Tevatron Top Quark Mass

MeasurementMeasurementNew combined Run I result (Was mt = 174.35.1 GeV)

mt = 178.04.3 GeV

Run II top quark mass results from both detectors are available

TeV EWWG is working on combining Run II top mass measurement from CDF and DØØ

Systematic error (mainly jet energy scale)

is becoming limiting accuracy factor


CDFSearch for Single Top Quark Search for Single Top Quark

ProductionProductionEW production of top quark direct probe of |Vtb| search for new physics

Events selection: is similar to top pairs in l+jets mode, but with lower jets multiplicity backgrounds (W+jets, tt, di-bosons) are substantial

95% C.L. limits CDF DØ

s-channel) <13.6pb <19pb

t-channel) <10.1pb <25pb

s+t channels) <17.8pb <23pb

Need above 1 fb-1

for observation


CDF Unexpected Top Quark Decay Modes?Unexpected Top Quark Decay Modes?

Assuming three-generation CKM matrix unitarity, |Vtb|~1.0

R = BR(tWb)/BR(tWq) ~1.0

Can measure ratio by checking the b quark content of the top sample decay products

If efficiency to tag a b quark is b (~0.45 at CDF), then

2=(bb)2

1=2bb(1-bb)

0=(1-bb)2

“double tag”

“single tag”

“no tag”

BR(tWb)/BR(tWq) >0.62 at 95% C.L.

Does top decays into something besides SM Wb? Like Xb, where X qq (100%) or Yb, where Y l(100%)?

Estimate branching limits using ratio of top cross sections ll/lj

Br(t Xb) <0.46 at 95% C.L. Br(t Yb) <0.47 at 95% C.L. (CDF)

R(b-light)


CDF Is Top to Wb vertex SM? W HelicityIs Top to Wb vertex SM? W Helicity

Test of V-A coupling in top decays: in SM W couples only to LH particlesThis together with angular momentum conservation allows top to decay into LH(negative helicity) or longitudinally-polarized (0 helicity) W bosons

In SM F-=0.30, F0 =0.70, F+ =0

Helicity of W manifests itself in decay product kinematics

CDF (l+jets and di-lepton)

DØØ (l+jets, 160 pb-

1)

No deviations from SM predictions

F+ < 0.24 at 90% C.L.

topologicalF+ < 0.24 at 90% C.L.

b tagging

)(17.0)(27.0 35.021.00 syststatF


CDF Experimental Limits on Higgs MassExperimental Limits on Higgs Mass

Available experimental limits

direct searches at LEP MH >114 GeV at 95% C.L.

precision EW fits

Light Higgs favored

GeVm 6945H 114

GeVm 260H at 95% C.L.

Tevatron provides:Precision mt and Mw measurements

Direct searches SM Higgs

non-SM Higgs

LEP


CDFSM Higgs Production and Decays at SM Higgs Production and Decays at

TevatronTevatron

ProductionDecay

s

Production cross section in the 1 pb range for gg H in the 0.1 pb range for associated vector boson production

Decays bb for MH < 130 GeV WW for MH > 130 GeV

Search strategy: MH <130 GeV associated production and bb decay W(Z)H l(l) bb

Backgrounds: top, Wbb, Zbb… MH >130 GeV gg H production with decay to WW

Backgrounds: electroweak WW production…


CDFSM Higgs Search: WH SM Higgs Search: WH l lbb (Mbb (MHH<130 <130

GeV)GeV)DØØ uses sample of W(e)+2 b tagged jets Require exactly 2 jets to suppress top

background2.5 events expected and 2 events observed

(WH)xBR(Hbb) < 12.4 pb at 95% C.L.

For MH =115 GeV

Future improvements Extend b-tagging

acceptance, efficiency Additional kinematic

variablesBetter Mbb resolution Add bb channel

CDF uses e and channels

Requires at least 1 jet b tagged


CDFSM Higgs Search: H SM Higgs Search: H WW WW l lll(M(MHH >130 GeV) >130 GeV)

Search strategy: 2 high Pt leptons and missing Et

WW comes from spin 0 Higgs:leptons prefer to point in the same

direction

DØ Run II Preliminary

Higgs of 160 GeV

W+ e+

W- e-

H


CDF Current Limits on SM Higgs SearchCurrent Limits on SM Higgs Search

DØØ light (115 GeV) Higgs search limit(WH)xBR(Hbb) < 12.4 pb-1 at 95% C.L.

Both experiments set 95% C.L. on SM Higgs cross section x Br

Limits already exceeding Run I results


CDFTevatron SM Higgs Search: Tevatron SM Higgs Search:

OutlookOutlook

Updated in 2003 in the low Higgs mass region

W(Z)Hl(,ll)bb to include

better detector understanding

optimization of analysis

Sensitivity in the mass region above LEP limit starts at ~2 fb-1

Meanwhile optimizing analysis techniques understanding detectors better searching for non-SM Higgs with higher production cross sections or enhanced branching into modes with lower backgrounds

LEP

Tevatron

Ldt, fb-1


CDF Search for MSSM HiggsSearch for MSSM Higgs

MSSM predicts larger Higgs cross sections for some values of parameter space then SM

Using NLO cross section calculations and assuming no difference between A and h/H DØØ performs search for MSSM Higgs multi-jet high Et sample 3 or more jets b tagged


CDF Search for MSSM Higgs Search for MSSM Higgs

CDF searches for XAhpp /

With A decaying into pair ~8% branching at high tan lower backgrounds then bb pairsNo excess seen over backgrounds


CDF Search for HSearch for H++++/H/H----

Predicted by some beyond SM models like Left-Right Symmetric ModelsIf short lived: prominent signature – multiple high Pt

leptons, like sign di-lepton mass peak backgrounds: WZ, W+jets, conversions (e)

If long lived (c > 3 m): two high ionization tracks

q

q

l +

l +

l -

l -

*/Z

H--

H++

MH>134GeV

D0 (113 pb-1) M(HL) > 118 GeV () at 95% C.L.CDF (240 pb-1) M(HL) > 136 GeV () at 95% C.L.

Background < 10-5


CDF Tevatron Top and Higgs: SummaryTevatron Top and Higgs: Summary

Top studies are actively progressing: updated tt, mt , limits on single top production studies of SM predictions and beyond SM models

W helicity studies decay modes: Wq, WX, Xq... tt resonances,…

Many excellent talks about top and Higgs studies at Tevatron are presented at ICHEP04 EW, Beyond SM, Heavy Quarks sessions

Higgs search is in progress: SM Higgs sensitivity (mH >114 GeV) starts at ~2 fb-1

non-SM Higgs many different models tested already see reduction in allowed phase space (Run I, LEP)

Expect substantial improvements in top studies, Higgs hunting with~0.5 fb-1 already on tapes~8 fb-1 expected in Run II

No deviations from SM observed (yet)


CDFExpected Run II Top Quark Studies Expected Run II Top Quark Studies

AccuracyAccuracy

Measurement Precision

Top Mass 2-3 GeV/c2

(ttbar) 9%

(ll)/(l+j) 12%

B(t Wb) 2.8%

B(Wlongitudinal) 5.5%

Vtb 13%

B(t c) 2.8 X 10-3

B(t Zc) 1.3 X 10-2

Some measurement targets to aim for in Run I I


CDF Search for H Search for H

In the SM Higgs has Br~10-3 search for SM Higgs decaying to gamma pair is not practical at Tevatron

Many SM extensions allow enhanced gamma pair decay rate largely due to suppressed coupling to fermions Fermiphobic Higgs Topcolor Higgs

Search strategy: Look for peaks in mass spectrum for high Pt isolated ’s


CDF Experimental ChallengesExperimental ChallengesCollecting data at energy frontier is non-trivial

Large particle fluxes irradiation issues

Small bunch spacing and large number of interactions per crossing

event synhronization complex event topology

Unexpected…CDF central tracking chamber aging resolved

Not new physics, just welding induced noise resolved


CDF Resonances in tt system?Resonances in tt system?

MX > 560 GeV

No resonance production in tt system is expected in SM

Some models predict tt bound states, example: topcolor-assisted technicolor predicts leptophobic Z’ with strong 3rd generation coupling

Experimental check: search for bumps in tt effective mass spectrum

DØ, 125 pbØ, 125 pb-1-1

Background

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Results for Top and Higgs at Tevatron

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