antónio onofre (onofre@lipc.fis.uc.pt)

António Onofre António Onofre (onofre@lipc.fis.uc.pt)(onofre@lipc.fis.uc.pt)

Moscow July 26 –Moscow July 26 – AuAugust 2, 2006gust 2, 2006

XXXIII InternationalXXXIII International Conference on High Energy Conference on High Energy PhysicsPhysics

On behalf of the ATLAS+CMS Collaborations

Testing the SM in tt and Testing the SM in tt and single top productionsingle top production

OutlineOutline

2) Single top @ LHC: 2) Single top @ LHC:

3) Conclusions3) Conclusions

Production Cross sectionProduction Cross section

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

1) tt @ LHC1) tt @ LHC tt Cross sectiontt Cross section Top spin correlationsTop spin correlations Probing the Wtb vertexProbing the Wtb vertex FCNC top decaysFCNC top decays

What do we know about the top quark?What do we know about the top quark? The top quark completes the three family structure of The top quark completes the three family structure of

the SMthe SM Its massive Its massive Spin=1/2,Spin=1/2, Charge=+2/3,Charge=+2/3, Isospin=+1/2Isospin=+1/2 ttbWbW

Large Large =1.42GeV (m=1.42GeV (mbb,M,MWW,,ss,EW corr.),EW corr.)

Short lifetimeShort lifetimehad QCD-1 >> decay

“t-quarks are produced and decay as free particles”

NO top hadrons

m/m <2%

-4/3 excluded @ 94%C.L.(D0)

c<52.5m @95%C.L.(CDF)

Not directly

The TEVATRON is probing better than ever the top sector…The LHC will allow precision measurements of Top Quark

PhysicsMoscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

~100%

Not directly

1) tt @ LHC1) tt @ LHC

~ 833pb @ 14TeV

Production X-section:Production X-section:

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

2 b-jets

pT>20 GeV

pT>20 GeV

≥4 jets (R=0.4) pT>40 GeV t (had)

t (lep)

W (had)

Clean Topology: tt back to back

Used for several studies

Semileptonic Topology:Semileptonic Topology:

+(90%) (10%)

Golden Channel

tt cross tt cross sectionsection

1) tt @ LHC1) tt @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

Selected 87000 signal events for L=10fb-1 (S/B~78, ~12 with back)

Although errors are dominated by systematics It seems possible to determine mt @ 1GeV level

(with L=10fb-1)

(=3.5%)

mmt (had)t (had)

Comb.

=10.6GeV

Systematic Errors:Systematic Errors:

tt cross tt cross sectionsection

1) tt @ LHC1) tt @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

Syst.(dominant): btag(7%), PDF(3.4%), PileUp(3.2%)Back.(dominant):tt,W+jets= 6.3%

A) Semi-leptonic channel (ttbbqql):

tt/tt= 9.7%(syst)±0.4%(stat)±3%(lum)

L=10fb-1CERN/LHCC 2006-021

CMS TDR 8.2

B) Di-leptonic channel (ttbb llll):L=10fb-1

Syst.(dominant):PDF(5%),btag(4%),JES(4%)

Back (dominant): ttll.(W, leptons)

= 5% (S/B=5.5)

tt/tt= 11%(syst)±0.9%(stat)±3%(lum)

tt cross tt cross sectionsection

With Tau leptons (ttbb ll, hadrons):

tt/tt= 16%(syst)±1.3%(stat)±3%(lum)=2%, S/B~1, -tag=30% ]

C) Fully Hadronic channel:

tt/tt= 20%(syst)±3%(stat)±5%(lum)

L=1fb-1

=2%, S/B<1/9 (QCD) Sys: JES(11%), PileUp(10%)

Top Spin Top Spin CorrelationsCorrelations

1) tt @ LHC1) tt @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

(tLtL) + (tRtR) - (tLtR) - (tRtL)

(tLtL) + (tRtR) + (tLtR) + (tRtL)A=

Testing the tt Production X-section:

l+,t

lqq

t

Other angular distributions:

AD(LO)

AD(NLO)

-0.217-0.237

SM:

A(LO)A(NLO)

0.3190.326

Although t and t are produced unpolarized their spins are correlated

New Physics affects A

X=spin analysing power of X

SM:

1 dN 1

N dcos2( 1 – ADXX´cos)=

Top Spin Top Spin CorrelationsCorrelations

1) tt @ LHC1) tt @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

A) Spin correlations and angular distributions:

l,

tl,

q

t

q

B) Spin Asymmetries can also be used (X-check)

(for L=10fb-1 precision A,AD below 10% )(hep-ex/0605190, subm. to Eur.Phys.J.C)

(Eur.Phys.J.C44S2 2005 13-33)• Semileptonic + Dileptonic• Syst (Eb-jet,mtop,FSR)• ~4% precision-0.29

0.42

SMMtt<550 GeV

0.008 0.010AD

0.014 0.023A

Error (±stat ±syst)

L=10fb-1

(CERN/LHCC 2006-021, CMS TDR 8.2)

A

N(cos) -

N(cos) N(cos) +

N(cos)

= - ADXx´ 1

2Ãxx´

Probing the Wtb vertexProbing the Wtb vertex1) tt @ LHC1) tt @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

A) Test the tbW decay vertexMeasure W polarization (F0, FL, FR) through lepton angular distribution in W cm system:

Semilep. +

Dileptonic

• Syst ( Eb-jet,mtop,FSR )• F0 F0 ~ 2% ; FR ~ 0.01

0.000(mb=0)

0.297

0.703

SM

0.003 0.024FL

0.003 0.012FR

0.004 0.015F0

Error (±stat ±syst) (Mt=175 GeV)

(Eur.Phys.J.C44S2 2005 13-33)

L=10fb-1

cos(l*)

(1/

)d/d

cos(

l*)

Probing the Wtb vertexProbing the Wtb vertex1) tt @ LHC1) tt @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

B) Anomalous Couplings in the tbW decay

Angular Asymmetries: AFB, A+ and A-

AFBA+

A-

cos(cos(ll*)*)

AFB [t=0] A± [t= (22/3-1)]±±

SM(LO):SM(LO):

(PRD67 (2003) 014009, mb≠0)

Probing the Wtb vertexProbing the Wtb vertex1) tt @ LHC1) tt @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

1 Results:

B) Anomalous Couplings in the tbW decay

SM(LO):

L=0.423R=0.0005 (mb≠0)

L=10fb-1

FCNC in top quark FCNC in top quark decaysdecays

1) tt @ LHC1) tt @ LHC

The top quark almost always decays to a b quark, B(tWb)~1

B(tWs)<0.18%, B(tWd)<0.02% (other decays are really rare) FCNC decays are highly suppressed in the SM:

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

At LHC Look for:

hep-ph/0409342APPB35(2004)2695

FCNC top FCNC top decaysdecays

1) tt @ LHC1) tt @ LHCB) In the absence of signal:B) In the absence of signal:

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

With 10 fb-1 already two orders of magnitude better than LEP/HERA/TEVATRON

A) 5A) 5 Sensitivity: Sensitivity:

L=10fb-1

L=10fb-1

ATLAS: Br(tqg@95%CL)<0.14%

Production Cross Production Cross Section Section

2) Single top @ LHC2) Single top @ LHC

Three different Processes (never observed yet)

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

[ PRD 70 (2004) 114012, PL B524 2002 283-288 ]

• Quark-gluon luminosity inside b-quark (PDF)• Renormalization scale ()• top mass (mtop=4.3GeV W*) changed by 3%)

Theoretical uncertainties:

Powerfull Probe of Vtb ( Vtb/Vtb~few% @ LHC )

t-channel Wt-channel W* (s-channel)

~ 250 pb ~70pb ~ 10 pb

VtbVtb Vtb

Vtb

Probe New Physics Differently: ex. FCNC affects more t-channel ex. W´ affects more s-channel[ PRD63 (2001) 014018 ]

Production Cross Production Cross Section Section

2) Single top @ LHC2) Single top @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

Common feature: 1 lepton, pT>25GeV/cHigh Missing ET

2 jets (at least 1 b-jet)(ATL-COM-PHYS-2006-002)

(ATL-PHYS-PUB-2006-014)

t-channel/= 8%(syst)±2.7%(stat)±5%(lum)Wt-channel/= 23.9%(syst)±8.8%(stat)±9.9%(MC)s-channel/= 31%(syst)±18%(stat)±5%(lum)

L=10fb-1

L=30fb-1

(CERN/LHCC 2006-021, CMS TDR 8.2)

Separate Channels by (Nj,Nb) in final state:

( <1.5%)

t-channel: Stat: 7000 events (S/B=3)Syst: dominated by Eb-jet and Lum. ErrorBack: tt, Wbb and W+jets(Nj=2,Nb=1)

Wt-channel:

Stat: ~1% (S/B=15%) ( ~ 4%)(Nj=3,Nb=1)

s-channel:

Stat: 1200 events for tb (S/B=10%)Syst: Eb-jet, Lum. Error, back X-section

( ~7-8%)(Nj=2,Nb=2)

3) Conclusions3) Conclusions

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

The LHC will be a top factory (8 million events already with 10fb-

1)

New era on precision Top Quark Physics

will start with the LHC: couplings, asymmetries, decays, etc.

will be measured with unprecedented precision

Stay tuned for next year

Backup SlidesBackup Slides

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

σ(W→lν)

σ(tt)mt=175 GeV

(pp tt):

q

q

t

t 10%

t

t

g

g 90%

High Collision Rate LHC (Tevatron) – every 25ns (396ns)

High Cross-Sections ~0.1b 2-3 interactions per collision

• LHC low/high lumi L=1033cm-2s-1

20 interactions per collision• LHC design/high lumi L=1034cm-2s-1

W, Z, top are rare events Requires High Luminosity Trigger is crucial: sel. Leptons High pT

Cross-sections at the LHCCross-sections at the LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

ATLAS ExperimentATLAS Experiment

Toroide+Solenoid (4 magnets) in inner cavityCalorimeters outside field

MAGNETSTracker

Si pixels + stripsTRD alows particle IDSolenoid B=2T/pT ~ 5x10-4 pT 0.01

Electromagnetic Calo

Pb-liquid argon/E ~ 10%/E ~1% uniform

Hadronic Calo

Fe-scint Tile Calo (10) /E ~ 50%/E 0.03

Muon Detectors

/pT < 10 % at 1 TeV

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

tt @ LHCtt @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

With only L=100pb-1 (few days of nominal low-lumi LHC operation)

We can easily see top peak without b-tag requirement

Mjjj (GeV)

electron+muon estimate for L=100 pb-1

Even

ts /

4.1

5 G

eV

ATLAS preliminary

3-jet invariant mass

Top-combinatorialand W+jets background

thad=highest pT,3j

W=highest pT,2j

(in thad system)

No b-tag and MW cut

(=5.3%)

tt cross section and top tt cross section and top massmass

ATLAS ExperimentATLAS Experiment

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ID B

ID A J

N

Cold tests

Limited access (ECT partially inside, half truck)

ID C

Pix

el

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Endcap Cal. A services

Cold tests

ID Barrel connection and testing (side C access via lift only!)

Sep '07 Oct '07

EO, side A

Oct '07

JF

Sep '07Oct '06

Jun '07

Big Wheels in park position

JD

Tru

ck

clos

ing

Big Wheel tooling

Endcap Cal. services

Muon Barrel C

LAr C cool down

Aug '07

Jul '07 Aug '07

VT

VT

JF

VJ

Barrel

Muon Barrel C completion

VA

Global Commissioning

EO, side CSmall

Wheel C

Jul '07

Side A

Glo

bal C

omm

issi

onin

g

glob

al te

sts,

pum

p do

wn

& b

ake

out

Side C

VJ

JF

Limited access

JFSide C

Barrel

Side A

ID services along Barrel & through Muons

Chains

May '07 Jun '07

VA

Small Wheel A

Big Wheel A (TGC1 +MDT+TGC2+TGC3)

Mar '07Feb '07Jan '07 Apr '07

ECT on beam line, partially inside (half truck)

Dec '06Nov '06

Nov '06 Jan '07Dec '06

Tru

ck

JT

Mar '07

Endcap Toroid A cooldown

& test

May '07Jul '06 Feb '07Sep '06 Oct '06Aug '06 Apr '07Jun '06

Sep '06Jul '06

Services 1st fixop

en

clos

e

Jun '06 Aug '06

open

ing

Barrel Calo testing and commissioning

ID access via lift only

map

ping

Fiel

dCable chains

BT pumping, cooling, testing

Endcap Toroid C cooldown & test

(Park pos.)

Endcap Toroid C

open

ing

TGC1

Endcap Cal. C testing & commissioning

ID A connection and testingPixel connection and testing

Endcap Toroid A

Muon Barrel AJT

Big Wheels C (TGC1+MDT +TGC2 +TGC3)

IDC connection and testing

LAr A cool down

BT test Magnet test

Time until Friday, August 31, 2007

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

CMS ExperimentCMS Experiment

1 Solenoid (B=4T)Calorimeters inside field

MAGNETTracker

Si pixels + stripsNo particle ID/pT ~ 1.5x10-4 pT 0.005

Electromagnetic Calo

PbWO4 Crystals /E ~ 2-5%/Eno longitudinal segmentation

Hadronic Calo

Brass-scint. (> 5.8 )/E ~ 100%/E 0.05

Muon Detectors

/pT ~ 5% at 1 TeVcombining with tracker

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

Sensitivity to New PhysicsSensitivity to New Physics

Single top @ LHCSingle top @ LHC

Moscow,Moscow, ICHEP 2006 ICHEP 2006 28 July 200628 July 2006

t-channel/ ~10%(tot)s-channel/ ~36%(tot)

L=10fb-1

CERN/LHCC 2006-021CMS TDR 8.2

Tait,Yuan PRD63 (2001) 014018

1-bands (SM )L=10fb-1