Searches for New Physics in Searches for New Physics in the Top Quark Samples at the Top Quark Samples at

CDFCDFLuca ScodellaroLuca Scodellaro

Instituto de Fisica de CantabriaInstituto de Fisica de CantabriaFor the CDF CollaborationFor the CDF Collaboration

HADRON07HADRON07XII International Conference on Hadron XII International Conference on Hadron

Spectroscopy Spectroscopy October 8October 8thth-13-13thth, , 2007, 2007, Frascati (Italy)Frascati (Italy)

MotivationMotivationss Top quark is really massiveTop quark is really massive

Lot of top properties still to be testedLot of top properties still to be tested

Samples getting larger and well Samples getting larger and well understoodunderstood

Yukawa coupling to Higgs near unityYukawa coupling to Higgs near unity Special role in EWSB?Special role in EWSB? Sensitivity to physics beyond SM?Sensitivity to physics beyond SM?

Direct searches for new phenomenaDirect searches for new phenomena

Top chargeTop charge,, width width, couplings, couplings Production mechanism Production mechanism

The TevatronThe Tevatron and CDF and CDF Proton-antiproton colliderProton-antiproton collider -- s = 1.96 TeVs = 1.96 TeV -- Record luminosity 2.9x10Record luminosity 2.9x103232cmcm-2-2ss-1-1

- Aim to collect 6-8 fb- Aim to collect 6-8 fb-1-1 by 2009 by 2009 Only top factory in the worldOnly top factory in the world

Tracking systemTracking system - charged particles and b-- charged particles and b-

taggingtagging EM and HAD calorimetersEM and HAD calorimeters - electrons and jets - electrons and jets Muon chambersMuon chambers

Calorimeters

Tracking system

Muon chambers

Integrated Luminosity at CDF

TTop Production at the op Production at the TevatronTevatron

Pair production via strong interaction Pair production via strong interaction dominant dominant

NLONLO ( (pp pp tt tt) ) 6.7± 0.8 pb 6.7± 0.8 pb

for mfor mtt = 175 GeV/c = 175 GeV/c22

Cacciari et al. JHEP 0404:068 (2004)Cacciari et al. JHEP 0404:068 (2004) Kidonakis & Vogt PRD 68 114014 (2003)Kidonakis & Vogt PRD 68 114014 (2003)

Decay via electroweak Decay via electroweak interaction interaction BR(tBR(tWb) ≈100%Wb) ≈100% Observed final states given by W boson Observed final states given by W boson

decaydecayDilepton: tt Dilepton: tt l lννllννbb bb (5%)(5%)Lepton+jets: Lepton+jets: tt tt lvqqbb lvqqbb (30%)(30%)Hadronic: Hadronic: tt tt qqqqbb qqqqbb (45%)(45%)

l=electron or muonl=electron or muon}}

qq

e

qq

e

-- --

Top Quark Samples at CDFTop Quark Samples at CDF Dilepton sampleDilepton sample

Lepton+jets sampleLepton+jets sample

About 1-1.7 fbAbout 1-1.7 fb-1-1 analyzed analyzed Cross section measuredCross section measured

Two high-PTwo high-PTT isolated leptons isolated leptons Two high-ETwo high-ETT jets jets Large missing transverse energyLarge missing transverse energy

One high-POne high-PTT isolated lepton isolated lepton ≥≥ 4 high-E4 high-ETT jets ( jets (≥≥11 b-tagged) b-tagged) Large missing transverse energyLarge missing transverse energy

Good agreement with SM predictionGood agreement with SM prediction Sample composition well understoodSample composition well understood

What Can We Test?What Can We Test?

l+

t

t

pp

--

W+

W-

ν

b

b- qq’- top propertiestop properties

top couplingstop couplings

top masstop mass top chargetop charge top widthtop width

V+A weak couplingV+A weak coupling Flavor ChangingFlavor Changing Neutral Current Neutral Current

(gg(ggtt)/tt)/(pp(pptt)tt) ffoorwardrward--backwardbackward asymmetryasymmetry

new particles new particles tt resonancestt resonances massive t’massive t’ heavy W’heavy W’

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top production mechanismtop production mechanism-- -- --

Top Quark PropertiesTop Quark Properties

Top Quark MassTop Quark Mass Challenging measurementChallenging measurement -- final state reconstructionfinal state reconstruction - jet energy measurement- jet energy measurement - neutrinos undetected- neutrinos undetected

Best world measurement Best world measurement lepton+jets channel:lepton+jets channel: mmtt = 17 = 1722..77 ± 2. ± 2.11 GeV/c GeV/c22

Tevatron combination Tevatron combination March’07March’07 mmtt = 170.9 ± 1.8 GeV/c = 170.9 ± 1.8 GeV/c22

New!!!

Constraints on Higgs Boson Constraints on Higgs Boson MassMass

Top mass (together with W) Top mass (together with W) mass measurements allow to mass measurements allow to constrain Higgs boson mass constrain Higgs boson mass through radiative corrections through radiative corrections

Electroweak fit to SM Higgs Electroweak fit to SM Higgs boson mass using latest boson mass using latest Tevatron combination:Tevatron combination:

MMHH=76=76+33+33-24 -24 GeV/cGeV/c2 2

MMHH<1<14444 GeV/c GeV/c2 2 @ 95% CL@ 95% CL

Top Charge: +2/3 or -4/3?Top Charge: +2/3 or -4/3? Suggestions for a fourth generation quark with Q=-Suggestions for a fourth generation quark with Q=-

4/34/3 D. Chang et al.D. Chang et al. PRD 59 091503(99)PRD 59 091503(99) Top charge reconstructedTop charge reconstructed from decay product tfrom decay product tWb Wb

Observed charge distribution tested vs Q=+2/3 and Observed charge distribution tested vs Q=+2/3 and Q=-Q=- 4/3 hypotheses4/3 hypotheses data consistent with a SM top hypotesisdata consistent with a SM top hypotesis

exotic quark excluded at 87% CLexotic quark excluded at 87% CL

W charge from leptonic W charge from leptonic decay Wdecay W±± ll±±vv b flavor from charged b flavor from charged tracks information in jettracks information in jet

Top Top Quark Quark WidthWidth Top lifetime in SM extremely short (Top lifetime in SM extremely short (ττtt~~

4x104x10-25-25s)s) Top mass spectrum Top mass spectrum sensitive to top width: sensitive to top width: templetes fit to extract templetes fit to extract tt

Compare Compare ttfitfit to results to results

from pseudo-from pseudo-experiments experiments t t < 12.7 GeV @ 95% < 12.7 GeV @ 95% CLCL ττtt>5.2x10>5.2x10-26-26 s @ 95% s @ 95% CL CL

Top Production MechanismTop Production Mechanism

σσ(gg(gg→tt)/→tt)/σσ(pp →tt)(pp →tt) Fraction of tt events from gluon fusion providesFraction of tt events from gluon fusion provides - test perturbative QCD- test perturbative QCD - sensitivity to new top - sensitivity to new top production and decayproduction and decay First idea: radiation from gluons tends to carry low P First idea: radiation from gluons tends to carry low P

fractionfraction

~85% ~15%

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Low-PLow-PT T track track multiplicitymultiplicity measured in no-measured in no-gluon and gluon-rich gluon and gluon-rich samplessamples

Fitting data Fitting data distribution to distribution to <N<NTRKTRK> templates> templates

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(gg(ggtt)/tt)/(pp(pptt) = 0.07 tt) = 0.07 ±± 0.16 0.16-- -- --

Second idea: top-antitop spin correlation Second idea: top-antitop spin correlation - like-sign in gluon fusion - like-sign in gluon fusion productionproduction -- unlike-sign in qq annihilationunlike-sign in qq annihilation Neural Network approach:Neural Network approach: - 2 kinematic variables describing the production in tt - 2 kinematic variables describing the production in tt

frame frame - 6 angles between decay products - 6 angles between decay products →→ spin correlation spin correlation

Fitting data to NN output shapesFitting data to NN output shapes

σσ(gg(gg→tt)/→tt)/σσ(pp →tt)(pp →tt)-- -- --

(gg(ggtt)/tt)/(pp(pptt)tt)<0.33 @ 68% CL<0.33 @ 68% CL-- ----

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Forward-Backward Forward-Backward AsymmetryAsymmetry

Production diagrams interferenceProduction diagrams interference NNtt (cos (cos ) – N) – Ntt (cos (cos )) NNtt (cos (cos ) + N) + Ntt (cos (cos )) 4-6% asymmetry expected at NLO4-6% asymmetry expected at NLO Use Use ΔΔY*QY*Qll in in lepton+jets lepton+jets sample: sample: AAΔΔY*QY*Q

NLONLO~~4-7% 4-7%

AAfb fb = 28= 28 ± 13(stat) ± 5(syst) %± 13(stat) ± 5(syst) %

AAfb fb == --

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Searches for Non-SM Searches for Non-SM Top Top CouplingsCouplings

Right-Handed Weak Right-Handed Weak CouplingCoupling

+1/2t W

+1/2

0W

b

V+A coupling signal of new physics V+A coupling signal of new physics - Left-right symmetry, PRL 38,1252(1977)- Left-right symmetry, PRL 38,1252(1977) - Mirror particles, J.Phys.G 26,99 (2000)- Mirror particles, J.Phys.G 26,99 (2000) - - Beautiful mirrBeautiful mirrors, PRD 65,53002,(2002)ors, PRD 65,53002,(2002) V-A character of top decay tested by W V-A character of top decay tested by W

helicity helicity

tb

W

+1/2-1/2

+1

t W

b

+1/2+1

-1/2

W0 longitudinal fraction F0 = 0.7

W- left-handed fraction F- = 0.3

W+ right-handed fraction F+ = 0.0

Suppressed in SM

Two variables sensitive to W helicity in top Two variables sensitive to W helicity in top decaysdecays

ccosos* = angle between lepton * = angle between lepton and top in W rest frame:and top in W rest frame: - Left-handed - Left-handed ~ ~ (1- (1- coscos**))22

- Longitudinal - Longitudinal ~ ~ (1- (1- coscos22**)) - Right-handed - Right-handed ~ ~ (1+(1+coscos**))22

Mass of the charged leptonMass of the charged lepton -- b quark system:b quark system: - M- Mlblb

22 (m (mtt2 2 - m- mWW

22) cos ) cos **

W Helicity in Top DecayW Helicity in Top Decay

338833443388

1122__

__

__

__

W Helicity ResultsW Helicity Results Different fitting techniques in cDifferent fitting techniques in cosos** analysis analysis Binned fit to theoretical shapes:Binned fit to theoretical shapes: - - ff0 0 = 0.38 ± 0.22 (stat) ± 0.07 (syst) = 0.38 ± 0.22 (stat) ± 0.07 (syst) ff++ = 0.38 ± 0.22 (stat) ± 0.07 (syst)= 0.38 ± 0.22 (stat) ± 0.07 (syst) - - ff+ + < 0.12 @ 95% CL< 0.12 @ 95% CL ((ff0 0 = 0.7= 0.7 fixed)fixed) Unbinned fit to Monte Carlo shapes:Unbinned fit to Monte Carlo shapes: -- ff0 0 = 0.61 ± 0.20 (stat) ± 0.03 (syst) = 0.61 ± 0.20 (stat) ± 0.03 (syst) ff++ = -0.02 ± 0.08 (stat) ± 0.03 (syst)= -0.02 ± 0.08 (stat) ± 0.03 (syst) -- ff+ + < 0.07 @ 95% CL< 0.07 @ 95% CL ((ff0 0 = 0.7= 0.7 fixed)fixed) Using MUsing Mlblb to measure fraction of V+A: to measure fraction of V+A: - f- f++ < 0.09 @ 95% CL< 0.09 @ 95% CL ((ff0 0 = 0.7 fixed)= 0.7 fixed)

FCNC: t FCNC: t Zq Zq In SM In SM BR(t BR(t Zq) = O(10 Zq) = O(10–14–14)) BSM scenarios allow BSM scenarios allow BRBR up to up to O(10 O(10––22)) - J.A.Aguilar-Saavedra, - J.A.Aguilar-Saavedra, Acta Phys.Polon.B35, 2695-2710Acta Phys.Polon.B35, 2695-2710 LEP limit BR(t LEP limit BR(t Zq) Zq) << 13.7%13.7% Counting experiment tt Counting experiment tt Zq Wb Zq Wb - Z - Z l l++ll--

- W - W qq’ qq’ - - 22 of kinematic fit to top mass of kinematic fit to top mass best discriminatorbest discriminator No excess observed No excess observed BR(t BR(t Zq) Zq) < 10.6% @ 95% CL < 10.6% @ 95% CL

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Searches for New ParticlesSearches for New Particles

tt Resonancestt Resonances-- Several models suggest tt resonant productionSeveral models suggest tt resonant production::

Fit to reconstructed tt massFit to reconstructed tt mass Model: narrow Z’ (Model: narrow Z’ (Z’Z’ ~~ 1.2% M1.2% MZ’Z’) ) no interference with s-channel ttno interference with s-channel tt No deviation from SM observedNo deviation from SM observed

Extended gauge theoriesExtended gauge theories - - A.Leike, A.Leike, Phys.Rep.317,143(1999)Phys.Rep.317,143(1999) KK states of gluons or ZKK states of gluons or Z - - B.Lillie et B.Lillie et al.,arXiv:hep-ph/0701166al.,arXiv:hep-ph/0701166 - - R.Rizzo,Phys.Rev.D61,055005(2000)R.Rizzo,Phys.Rev.D61,055005(2000) Axigluons and TopcolorAxigluons and Topcolor - L.Sehgal et - L.Sehgal et al.,Phys.Lett.B200(1988)al.,Phys.Lett.B200(1988) - C.Hill et - C.Hill et al.,Phys.Rev.D49,4454(1994)al.,Phys.Rev.D49,4454(1994)

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σσ (Z’(Z’→→tt) < 0.7 pb @ 95% CLtt) < 0.7 pb @ 95% CL for Mfor MZ’Z’ > 700 GeV/c > 700 GeV/c22

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Search for Search for MassiveMassive t’ t’ →→ Wb Wb 44thth generation of heavy fermions compatible with generation of heavy fermions compatible with

EWK dataEWK data

2-dim likelihood fit to data2-dim likelihood fit to data

N=2 SUSY models: H.J.He et al., arXiv:hep-ph/0102144N=2 SUSY models: H.J.He et al., arXiv:hep-ph/0102144 “ “Beautiful mirrors” model: C.Wagner et al., Beautiful mirrors” model: C.Wagner et al., arXiv:hep-ph/0109097arXiv:hep-ph/0109097

HHTT: sum of transverse energy: sum of transverse energy of all objects in final state of all objects in final state Mreco: Wb reconstructed Mreco: Wb reconstructed mass mass

No evidence for t’ No evidence for t’ observedobserved Set 95% CL upper limit Set 95% CL upper limit onon (pp→t’t’) x BR(t’→Wb)(pp→t’t’) x BR(t’→Wb)22

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mmt’t’>256 GeV/c>256 GeV/c22 @ 95% @ 95% CLCL

Heavy W’ ProductionHeavy W’ Production Search for W-like heavy boson decaying to a top-Search for W-like heavy boson decaying to a top-

bottom pairbottom pair

Single top production signature:Single top production signature:

No evidence for W’ boson inNo evidence for W’ boson in reconstructed Mreconstructed Mwbbwbb mass spectrum mass spectrum Limits on W’ production and its Limits on W’ production and its couplings to fermionscouplings to fermions

Extra dimensions: PRD 74, 75008(2006)Extra dimensions: PRD 74, 75008(2006) Little Higgs: arXiv:hep-ph/051212Little Higgs: arXiv:hep-ph/051212 Topcolor: PL B385, 304(1996)Topcolor: PL B385, 304(1996)

Charged leptonCharged lepton Large missing energyLarge missing energy Two jetsTwo jets

σ∙σ∙BR(W’BR(W’→→tb)<0.4 pb @ 95% CL tb)<0.4 pb @ 95% CL for Mfor MW’ W’ > 700 GeV/c> 700 GeV/c22

ConclusionsConclusions The CDF top quark samples in 1-1.7 fbThe CDF top quark samples in 1-1.7 fb-1-1 of pp collision data at the Tevatron have of pp collision data at the Tevatron have

been established and well understoodbeen established and well understood

Lot of precision measurements and first Lot of precision measurements and first results in searches for new physics have results in searches for new physics have been achieved been achieved

Beginning to have sensitivity to Beginning to have sensitivity to unexpected top quark properties and unexpected top quark properties and new phenomena in our samplesnew phenomena in our samples

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Backup SlidesBackup Slides

b Quark Taggingb Quark Tagging Tagging the b quark improves parton-jet Tagging the b quark improves parton-jet

assignments:assignments: lepton+jets: 1 tag lepton+jets: 1 tag →→ 6 combinations, 2 tags 6 combinations, 2 tags →→ 2 2

combinationscombinations Requiring a b tagged jet also reduces Requiring a b tagged jet also reduces

background contaminationbackground contamination B hadrons are long livedB hadrons are long lived Jet tagging Jet tagging efficiency efficiency →→ 42% 42%

False tag rate False tag rate →→ 0.5% 0.5%

Best Top Mass Best Top Mass MeasurementMeasurement

Matrix Element Method with in situ jet calibrationMatrix Element Method with in situ jet calibration Build event likelihood as a function of mBuild event likelihood as a function of mtt and JES and JES

Sum over events and background subtractionSum over events and background subtraction logLlogLtottot(m(mtt,JES)= ( logL(y,JES)= ( logL(yii|mt,JES) – f|mt,JES) – fbgbg(y(yii)logL(bg|m)logL(bg|mtt,JES) ),JES) ) Top mass extracted by maximizing profile Top mass extracted by maximizing profile

likelihoodlikelihood LLprof prof (m(mtt) = max L) = max Ltottot(m(mtt, j), j)jєJESjєJES

ΣΣii

NormalizationNormalizationfactorfactor

AcceptanceAcceptance

Sum over partonSum over partonjet assignamentjet assignament

PDFsPDFsb-tagb-tagweightweight

Transfer functionTransfer functionconnecting partons to jetsconnecting partons to jets

Matrix Matrix elementelement

IntegrationIntegrationover phase spaceover phase space

Lowest Lowest 22 parton-jet assignamnt used in parton-jet assignamnt used in analysanalyseses

Correct combination in 70% of the casesCorrect combination in 70% of the cases

2

2

2

2

2

2

2

2

,2

2,,

jets 4,2

2,,2

)()()()(

)()(

t

tb

t

tbjj

W

W

W

Wjj

yxj j

measUEj

fitUEj

i i

measiT

fitiT

MMMMMMMM

pppp

Constrain on W massesConstrain on W masses t and t have the t and t have the same masssame mass MMtt

Fluctuate momenta according to their Fluctuate momenta according to their resolutionresolution

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Kinematic FitKinematic Fit

Search for t Search for t →→ H H++bb SMMS predicts large BR(tSMMS predicts large BR(t→H→H++b) (>10%) for small and b) (>10%) for small and

large large ββ Four different channels considered: Four different channels considered: HH+ + → → ττνν, , cs, tcs, t**b, b,

WW++hh00

Compare predictions to data to set limits on MCompare predictions to data to set limits on MH H - tan(- tan(ββ) ) planeplane

Scan all combinations of HScan all combinations of H++ BR’s to set model BR’s to set model independent limits on BR(tindependent limits on BR(t→H→H++b)b)

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