1 expectations for top quark physics in atlas at lhc clara troncon on behalf of the atlas...

1

Expectations for Top Quark Physics

in ATLAS at LHC

Clara TronconOn Behalf of the ATLAS CollaborationUniversità and INFN MilanoICHEP 2004

Top MassSingle top productionCouplings and decaysTop spin polarization

Clara Troncon - ICHEP 2004

P 2

LHC

TeVatron

Process (pb) N/s N/yearTotal collected before start of LHC

W l 3104 30 108 104 LEP / 107 FNAL

Z ee 1.5103 1.5 107 107 LEP

t t 830 1 107 104 Tevatron

b b 5108 106 1013 109 Belle/BaBar ?

Low lumi = 10 fb-1/y

(Opposite @ FNAL)

32121 10~ ; ˆ xxxsxs

~90% gg ~10% qq

LHC top factory !

Top pair production at LHC

LHC start up in April 2007 @ L=1033


P 3 Motivations for Top Physics studies

Top quark mass is a fundamental parameter of the EW theory In SM: top- and W-mass constrain Higgs mass

Sensitivity through radiative correctionsWant precision measurement of top mass to scrutinize SM

Large value of m(t) and (t) and short lifetime 10-24s make top quark unique Decays before hadronization Sensitive window for New Physics

Many new heavy particles produce top quarksDetailed properties of top probe SM & beyond

Top will be produced abundantly !

And in addition ... Experiment: Top quark useful to calibrate the

detector

Beyond Top: Top quarks will be a major source of background for almost every search for physics beyond the SM

direct

indirectEXCLU

DED

Summer 2003 result


P 4

Top decaysDi-leptons (e/)

BR≈4.9% 0.4x106 ev/yNo top reconstructedClean sample

Single Lepton (e/)BR=29.6% 2.5x106 ev/yOne top reconstructedClean sample

Fully HadronicBR≈45% 3.5x106 ev/yTwo tops reconstructedHuge QCD backgroundLarge combinatorial bckgnd

Tau + X BR≈21% 1.6 x106 ev/yNo top reconstructed

Lepton side

Hadron side

In the SM the top decays to W+b

All decay channels investigated Using ‘fast parametrized’detector response: Checks with detailed GEANT simulations


P 5

Golden channel BR 30% and clean trigger from isolated lepton

Important to tag the b-jets: enormously reduces background (physics and combinatorial)

Hadronic side

W from jet pair with closest invariant mass to MW

Require |MW-Mjj|<20 GeV

Ligth jet calibrated with Mw constraint

Assign a b-jet to the W to reconstruct Mtop

Leptonic side

Using remaining l+b-jet, the leptonic part is reconstructed

|mlb -<mjjb>| < 35 GeV

Kinematic fit to the t t hypothesis, using MW constraints

MTop from lepton+jet SN-ATLAS-

2004-040

Br(ttbbjjl)=30%for electron + muon

• Isolated lepton PT>20 GeV

• ETmiss>20 GeV

• 4 jets with ET>40 GeV R=0.4

• >1 b-jet (b60%, ruds102,

rc101)

Background: <2%

W/Z+jets, WW/ZZ/WZ

j1

j2

b-jet

t

70% top purity - efficiency 1.2 %


P 6

Top mass systematics

Method works: Linear with input Mtop

Largely independent on Top PT

Biggest uncertainties: Jet energy calibration FSR: ‘out of cone’ give

large variations in mass B-fragmentation

Verified with detailed detector simulation and realistic calibration

Source of uncertaintyHadronic Mtop (GeV)

Fitted Mtop (GeV)

Light jet scale 0.9 0.2

b-jet scale 0.7 0.7

b-quark fragm 0.1 0.1

ISR 0.1 0.1

FSR 1.9 0.5

Comb bkg 0.4 0.1

Total 2.3 0.9

Statistical 0.1 0.1

Challenge:

determine the mass of the top with~1 GeV accuracy in one year of LHC


P 7 Alternative mass determination

High PT semi-leptonic back to back events:

PT>200 GeV and hemisphere separation (bckgnd reduction, much less combinatorial) Higher probability for jet overlapping

Sum calo towers over a large R>0.8 Use the events where both W’s

decay leptonically (Br~5%) Much cleaner environment Less information available from two ’s S/B=10

Use the events where both W’s decay hadronically (Br~45%)

Difficult ‘jet’ environment Select PT>200 GeV, S/B=18

Mtop

Statistically independent samples

Different systematics but similar values < 3 GeV


P 8

Use exclusive b-decays with high mass products (J/)Higher correlation with Mtop Clean reconstruction (background free)BR(ttqqb+J/) 5 10-5 ~ 30% 103 ev./100 fb-1

(need high luminosity)

Top mass from J/

Different systematics (almost no sensitivity to FSR)

Uncertainty on the b-quark fragmentation function becomes the dominant error

Pttop

MlJ/

M(J/+l)M(J/+l)


P 9

Mtop(GeV)

L = 150 pb-1

(few days low lumi)

Commissioning phase:Assume pessimistic scenario:

No b-tagging

No jet calibration

But: Good lepton id

Semi-leptonic events selection Isolated lepton with PT>20 GeV

Exactly 4 jets with PT>40 GeV

Reconstruct top selecting 3 jets with maximal resulting PT

Kinematic constrained fit assuming MW1

=MW2 and MT1

=MT2

Signal (MC@NLO,Pythia,Herwig) + background (W+4j-Alpgen)

at initial phase of LHC Top peak visible, minimal

selection and reco (3-7 GeV)

Sample for b-tagging and jet scale calib. studiesΔσstat(t-tbar) ~ 2% (1 week) !!!

Commissioning


P 10

Search for Resonances Measure ( t t ) to < 10 % (stat.) with a few days of luminosity !! Could be first indication of new physics at the LHC (?)

Many theoretical models include the existence of resonances decaying to t t SM Higgs (BR smaller with respect to the WW and ZZ decays) MSSM Higgs (H/A, if mH,mA>2mt, BR(H/A→tt)≈1 for tanβ≈1) Technicolor Models, strong ElectroWeak Symmetry Breaking, Topcolor, “colorons” production, […]

Reconstruct m( t t ) to search for resonances Χ if σΧ, ΓΧ and BR(Χ t t ) predicted Study of semileptonic evts found :

mass resolution 6% and reconstruction efficiency 20% mtt=400 GeV - 15% mtt=2 TeV

1.6 TeV resonance

Mtt

xBR required for a discovery

mtt [GeV/c2]

σxB

R [

fb]

30 fb-1

300 fb-1

1 TeV

830 fb


P 11

Wg fusion: 245±27 pbS.Willenbrock et al., Phys.Rev.D56, 5919

Wt: 62.2 pbA.Belyaev, E.Boos, Phys.Rev.D63, 034012

W* 10.2±0.7 pbM.Smith et al., Phys.Rev.D54, 6696

EW Single Top Quark Production

Direct determination of the tWb vertex (=Vtb)

Discriminants:- Jet multiplicity (higher for Wt)

- More than one b-jet (increase W* signal over W- gluon fusion)- 2-jets mass distribution (mjj ~ mW for the Wt signal only)

Three production mechanisms at LHC:

Main Background [xBR(W→ℓ), ℓ=e,μ]:tt σ=833 pb [ 246 pb]Wbb σ=300 pb [ 66.7 pb]Wjj σ=18·103 pb [4·103 pb]

-3. 7+16.6

Wg [54.2 pb]

Wt [17.8 pb]

W* [2.2 pb]

1) Determination of Vtb

2) Independent mass measurement

3) Opportunity to measure top spin pol.

4) May probe FCNC

Pre -selection:

1 isolated lepton Pt>20 GeV

2 jets Pt>30 GeV

1 b-tagged jet Pt>50 GeV

+

Njets =2 or 3

Forward jet , pT>50 GeV (for Wg)

N-bjet=1 (for Wt) or =2 (for W*)


P 12

Signal unambiguous, after 30 fb-1:

Complementary methods to extract Vtb

With 30 fb-1 of data, Vtb can be determined to %-level or better(experimentally)

EW Single Top Quark Production

Can measure cross-sections for all 3 processes separately

important since each is sensitive to different kinds of possible new physics and diff. Vtb syst.

heavy W’ increase in the s-channel W*

FCNC gu t increase in the W-gluon fusion channel

For 30 fb-1, can measure Vtb with stat. error of 0.4% – 2.7% (dep. on process)

For W-gluon fusion, can measure predicted W and top helicity

sensitive to possible V+A contribution at level of few per cent

Detector performance critical: fake l, b-tag, forward jets, low E jets

ProcessVtb

(stat)Vtb

(theory)

Wg fusion 0.4% 6%

Wt 1.4% 6%

W* 2.7% 5%

Process Signal Bckgnd S/B

Wg fusion 27k 8.5k 3.1

Wt 6.8k 30k 0.22

W* 1.1k 2.4k 0.46


P 13 Top Quark Couplings and Decays

Does the top quark behaves as expected in the SM? Branching Ratios Electric charge Top spin polarization Yukawa coupling to Higgs from t t H events

Can be measured to <20% from t-tbar H production …….

According to the SM, top decays rather “uninteresting” Br(t W b) 99.9%, Br(t W s) 0.1%, Br(t W d) 0.01%

(difficult to measure)

Can probe t W[non-b] by measuring ratio of double b-tag to single b-tag Statistics more than sufficient to be sensitive to SM expectation for Br(t

W + s/d) Need excellent understanding of b-tagging efficiency/purity

Many Beyond SM models involve anomalous top couplings Several possible rare decay modes (eg FCNC) have clear experiment signatures

and, if observed at the LHC, would be evidence for new physics FCNC decays highly suppressed (Br< 10-13-10-10) and 10-3 to 10-5 sensitivity


P 14 Top Quark Couplings and Decays

Does the top quark behave as expected in the SM? Branching Ratios ACHIEVABLE Electric charge ACHIEVABLE with 10 fb-1

radiative tt events or t charge reconstruction Top spin polarization ACHIEVABLE with 10 fb-1

5 statistical significance for a non-zero value in di-lepton and semi-leptonic events Yukawa coupling to Higgs from t t H events ACHIEVABLE

Can be measured to <20% from t-tbar H production

According to the SM, top decays rather “uninteresting” Br(t W b) 99.9%, Br(t W s) 0.1%, Br(t W d) 0.01%

(difficult to measure)

Can probe t W[non-b] by measuring ratio of double b-tag to single b-tag Statistics more than sufficient to be sensitive to SM expectation for Br(t W + s/d) Need excellent understanding of b-tagging efficiency/purity

Many Beyond SM models involve anomalous top couplings Several possible rare decay modes (eg FCNC) have clear experiment signatures and, if

observed at the LHC, would be evidence for new physics FCNC decays highly suppressed (Br< 10-13-10-10) and 10-3 to 10-5 sensitivity


P 15

In the SM the FCNC decays are highly suppressed (Br<10-13-10-10)Several models of Physics Beyond SM can give HUGE enhancementsFCNC can be detected through top decay or single top production

Sensitivity according to ATLAS studies of top decays :

t Zq (CDF Br<0.137, ALEPH Br<17%, OPAL Br<13.7%) Reconstruct t Zq (l+l-)j Sensitivity to Br(t Zq) = 1.1 X 10-4 (100 fb-1)

t q (CDF Br<0.032) Sensitivity to Br(t q) = 1.0 X 10-4 (100 fb-1)

t gq Difficult identification because of the huge QCD bakground One looks for “like-sign” top production (ie. tt)Sensitivity to Br(t gq) = 7 X 10-3 (100 fb-1)

Top Quark FCNC Rare Decays


P 16

Top Charge determination ATL-

PHYS-2003-035

Can we establish Qtop=2/3?Currently cannot exclude exotic possibility Qtop=-4/3

Assign the ‘wrong’ W to the b-quark in top decays tW-b with Qtop=-4/3 instead of tW+b with Qtop=2/3 ?

Technique:Hard radiation from top quarks

Radiative top production, pptt cross section proportional to Q2top

Radiative top decay, tWb

On-mass approach for decaying top: two processes treated independently

Matrix elements havebeen calculated and fed intoPythia MC

Radiative top production

Radiative top decay


P 17

Top Charge Determination ATL-PHYS-

2003-035

Yield of radiative photons allows to distinguish top charge

Q=2/3 Q=-4/3

pptt 101 ± 10 295 ± 17

pptt ; tWb 6.2 ± 2.5 2.4 ± 1.5

Total background 38 ± 6

Determine charge of b-jet andcombine with lepton

Use di-lepton sample Investigate ‘wrong’

combination b-jet charge and lepton charge

Effective separation b and b-bar possible in first year LHC

Study systematics in progress

i

κ

i

i

κ

ii

bjet

pj

pjqq

pT()

events

10 fb-1

One year low lumi


P 18 Top Spin Correlations ATL-PHYS-2002-

024 ATL-PHYS-2003-012

In SM with Mtop175 GeV, (t) 1.4 GeV » QCD

Top decays before hadronization, and so can study the decay of ‘bare quark’ Decay products keep spin info Substantial ttbar spin correlations predicted in pair production

Can study polarization effects through helicity analysis of daughters

Study with di-lepton and semi-leptonic events Spin analyser:

Leptonic: lepton Hadronic: (W, b) or least energetic jet (lej) Interesting angles:Θ1 (Θ2) : angle between chosen spin axis

and spin analyzer direction in the t(t) rest frame.

Spin axis is t(t) direction in the parton c.m.s.

(helicity basis)

φ : angle between spin analyzers direction

in the t(t) rest frame

e+/+

top+

With helicity correlationNo helicity correlation

<CosΘ+ · CosΘ-> <CosΘ+ · CosΘ->

leptons)for 1 :qualityanalyser (spin

base)helicity in n correlatiospin of (degree 34.0

4

coscos1

coscos

1 2

C

C

dd

d


P 19 Top spin correlations ATL-PHYS-

2002-024 ATL-PHYS-2003-012

Also study spin correlations in semi- leptonic eventsLeast energetic jet from W decay: ~ 0.5

Results for S + B : 80500 S, S/B=15 with 10 fb-1

C(lej) = 0.21 0.015 0.04 = ~ 5 σ from 0 with 10 fb-1

Semi-leptonic analysis probe SM at 5 after 1 year at low lumi. Dileptonic analysis complementary and similar power.

30 fb-1

TopReX 4.05 (SM): LO spin correlation simulation

Pythia 6.221 (NC): hadronisation, fragmentation and decays with CTEQ5L structure function, ISR-FSR

AlpGen: used for W+jets background

Tauola+Photos 2.6: t decay and radiative corrections

Atlfast 2.60: ATLAS fast simulation and reconstruction


P 20

Conclusions

ATLAS will be able to provide many precise measurements of top quark properties

Precise determination of Mtop to 1 GeV seems achievable in 1 year of LHC

Crucial for EW physics, precision tests, constraints on Higgs sector, sensitivity to new physics

Confirmation that top-quark is SM particle and/or search for deviation from SM from:

Measure Vtb, charge, spin, decays ACHIEVABLEFirst new physics in ATLAS may come from top quark analysis

Early top signals will also be critical to detector commissioning Top peak should be visible with eyes closed and used for jet E cal, Et, b-

tag,high PT e/m

Lots of work remaining to be ready to fully exploit the top physics potential of the LHC (MC tuning, full sim., effect of real detector on studies - dead channels …)

LHC is top factory

( t t )~830 pb-1 + EW( t )~250 pb-1

107 events in first year

21

BACKUP SLIDES


P 22

Top mass systematics

Source of uncertaintySemi-

leptonic Mtop (GeV)

Fitted SemileptonicMtop (GeV)

Semileptoniclarge clusters

Mtop (GeV)

Di-leptonicMtop (GeV)

Hadronic

High pTMtop (GeV)

Statistics 0.1 0.1 0.2 0.3 0.2

Light jet scale 0.9 0.2 - - 0.8

b-jet scale 0.7 0.7 - 0.6 0.7

b-quark fragm 0.1 0.1 0.3 0.7 0.3

ISR 0.1 0.1 0.1 0.4 0.4

FSR 1.9 0.5 0.1 0.6 2.8

Comb bkg 0.4 0.1 0.1 0.2 0.4

PDF - - - 1.2 -

Mass scale calibration - - 0.9 - -

UE estimate (+_10%) - - 1.3 - -

Total systematics 2.3 0.9 1.7 1.7 3.0

Challenge:

determine the mass of the top with~1 GeV accuracy in one year of LHC


P 23m

ean

p

rob

.

Mtop

Top mass from di-leptons

Use the events where both W’s decay leptonically (Br~5%)Much cleaner environment Less information available due to two neutrino’s

Sophisticated procedure for fitting the whole event, i.e. all kinematical info taken into account (cf D0/CDF)

Compute mean probability as function of top mass hypothesis Maximal probability corresponds to top mass

Source of uncertainty

Di-lepton Mtop (GeV)

statistics 0.3

b-jet scale 0.6

b-quark fragm 0.7

ISR 0.4

FSR 0.6

pdf 1.2

Total 1.7

80000 events

(tt) = 20 %

S/B = 10

Mea

n pr

oba

bilit

y

mass

Selection:

2 isolated opposite sign leptons

Pt>35 and Pt>25 GeV

2 b-tagged jets

ETmiss>40 GeV


P 24

Top mass from hadronic decay

Use events where both W’s decay hadronically (Br~45%)Difficult ‘jet’ environment

(QCD, Pt>100) ~ 1.73 mb(signal) ~ 370 pb

Perform kinematic fit on whole eventb-jet to W assignment for combination

that minimize top mass differenceIncrease S/B:

Require pT(tops)>200 GeVSource of uncertainty

Hadronic Mtop

(GeV)

Statistics 0.2

Light jet scale 0.8

b-jet scale 0.7

b-quark fragm 0.3

ISR 0.4

FSR 2.8

Total 3.0

3300 events selected:

(tt) = 0.63 %

(QCD)= 2·10-5 %

S/B = 18

Selection

6 jets (R=0.4), Pt>40 GeV

2 b-tagged jets

Note: Event shape variables like HT, A, S, C, etc not effective at LHC (contrast to Tevatron)


P 25

High Pt sampleThe high pT selected sample deserves independent analysis:

Hemisphere separation (bckgnd reduction, much less combinatorial)Higher probability for jet overlapping

Use all clusters in a large cone R=[0.8-1.2] around the reconstructed top- direction

Less prone to QCD, FSR, calibration

UE can be subtractedj1

j2

b-jet

t

Statistics seems OK and syst. under control

R

Mtop Mtop


P 26

Uncertainty On b-jet scale: Hadronic

1% Mt = 0.7 GeV5% Mt = 3.5 GeV10% Mt = 7.0 GeV

Uncertainty on light jet scale: Hadronic

1% Mt < 0.7 GeV10% Mt = 3 GeV

Jet scale calibration

Calibration demands:Ultimately jet energy scale calibrated within 1%

Uncertainty on b-jet scale dominates Mtop: light jet scale constrained by mW

At startup jet-energy scale known to lesser precision

Scale b-jet energyScale light-jet energy

MTop MTop

±10%


P 27

Commissioning the detectorsDetermination MTop in initial

phaseUse ‘Golden plated’ lepton+jet

Selection: Isolated lepton with PT>20 GeVExactly 4 jets (R=0.4) with

PT>40 GeVReconstruction:

Select 3 jets with maximal resulting PT

Signal can be improved by kinematic constrained fit

Assuming MW1=MW2

and MT1=MT2

PeriodStat Mtop (GeV)

Stat /

1 year 0.1 0.2%

1 month 0.2 0.4%

1 week 0.4 2.5%No background

included

Calibrating detector in comissioning phase

Assume pessimistic scenario:

-) No b-tagging

-) No jet calibration

-) But: Good lepton identification


P 28

Commissioning the detectors

Signal plus background at initial phase of LHC

Most important background for top: W+4 jetsLeptonic decay of W, with 4 extra ‘light’ jets

Alpgen, Monte Carlo has ‘hard’ matrix element for 4 extra jets(not available in Pythia/Herwig)

ALPGEN:

W+4 extra light jets

Jet: PT>10, ||<2.5, R>0.4

No lepton cuts

Effective : ~2400 pb

With extreme simple selection and reconstruction the top-peak should be visible at LHC

L = 150 pb-1

(2/3 days low lumi)

measure top mass (to 5-7 GeV) give feedback on detector performance


P 29

Rare SM top decays

Direct measurement of Vts, Vtd via decays tsW, tdW

Decay tbWZ is near threshold

(mt~MW+ MZ+mb)

BRcut(t bWZ) 610-7

(cut on m(ee) is 0.8 MW)

Decay tcWW suppressed by GIM

factor BR(t cWW) ~ 110-13

If Higgs boson is light: tbWH FCNC decays: tcg, tc, tcZ (BR: 510-11 , 510-13 , 1.310-13 ) Semi-exclusive t-decays tbM

(final state 1 hadron recoiling against a jet:

BR(t b) 410-8, BR(t bDs) 210-7)

2 2b Wm M


P 30

Interesting: branching ratio depends strongly on Mtop

Since Mtop~MW+Mb+MZ

With present error mt 5 GeV, BR varies over a factor 3

B-jet too soft to be efficiently identified “semi-inclusive” study for a WZ near

threshold, with Z l+l- and W ->jjRequiring 3 leptons reduces

the Z+jets background

Sensitivity to Br(t WbZ) 10-3 for 1 year at low lumi. Even at high L can’t reach SM predictions ( 10-7 - 10-6)

G. Mahlon hep-ph/9810485

M(top) (GeV)

(t

WbZ

)/(t

Wb)

Rare decays: topWbZ


P 31

Various approaches studied Previously: ttbarHq Wb(b-bbar)j(lb)

for m(H) = 115 GeV Sensitivity to Br(t Hq) = 4.5 X 10-3

(100 fb-1)

New results for: t tbarHq WbWW*q Wb(l lj) (lb)

≥ 3 isolated lepton with pT(lep) > 30 GeV pTmiss > 45 GeV ≥ 2 jets with pT(j) > 30 GeV, incl. ≥ 1 jet con b-tag Kinematical cuts making use of angular correlations

Sensitive to Br(t Hq) = 2.4 X 10-3

for m(H) = 160 GeV (100 fb-1)

Signal

ttH

tt

Signal

ttH

tt

topHq


P 32

Non-SM Decays of Top 4thfermion family

Constraints on Vtqrelaxed:

Supersymmetry (MSSM) Observed bosons and fermions would have superpartners 2-body decays into squarks and gauginos (t H+ b )

Big impact on 1 loop FCNC two Higgs doublets

H LEP limit 77.4 GeV (LEP WG 2000) Decay t H+ b can compete with t W+ b 5 states (h0,H0,A0,H+,H-) survive after giving W & Z masses H couples to heaviest fermions detection through breakdown of e /

m / t universality in tt production

at ( ( )) ~ 3bBR t W b W c 10 m 100GeV

, , 01 1 1 1 1t t g t b t t


P 33

Alternative methods

Continuous jet algorithm Reduce dependence on MC Reduce jet scale uncertainty

Repeat analysis for many cone sizes R

Sum all determined top mass:robust estimator top-mass

Determining Mtop from (tt)?huge statistics, totally different systematics

But: Theory uncertainty on the pdfs kills the idea10% th. uncertainty mt 4 GeVConstraining the pdf would be very precious…(up to a few % might not be a dream !!!)

Luminosity uncertainty then plays the game (5%?)

Luminosity uncertainty then plays the game (5%?)


P 34

1cos22

2

WZ

W

m

m

No observable directly related to mNo observable directly related to mHH. However the dependence can . However the dependence can appear through radiative correctionsappear through radiative corrections. tree level quantities changedtree level quantities changed

mH

, , r r = f [ln(m= f [ln(mHH/m/mWW), m), mtt22]]

By making precision measurements (already interesting per se):By making precision measurements (already interesting per se):• • one can get information on the missing parameter mone can get information on the missing parameter mHH• • one can test the validity of the Standard Modelone can test the validity of the Standard Model

SMmfermions (9)

mbosons (2)

VCKM (4)

GF (1)

s(1)

)1(sin2 2

2 rG

mFW

W

The uncertainties on mThe uncertainties on mtt, m, mWW are the dominating ones in the electroweak fit are the dominating ones in the electroweak fit

predictions

(down to 0.1% level)

lepteffcbl

bclFBcblhWZWZ AARm 2

,,,,,00

,,0

,, sin,,,,,,

tWW mm ,,

had

W2sin

WW CsQ 2sin)(

LEP+SLD:LEP+SLD:

UA2+Tevatron:UA2+Tevatron:

NuTeV:NuTeV:

APV:APV:

eeeeqq l.e.:qq l.e.:

What we know..


P 35

Top mass: Where we are

In 2009 (if upgrade is respected) from Tevatron: Mtop = 1.5 GeV !!


P 36

Tevatron only (di-lepton events or lepton+jet ) from W decays

Status of inputs (preliminary):mmtt=(178.0 =(178.0 2.7 2.7 (stat) (stat) 3.3 3.3 (syst)(syst)) GeV/c) GeV/c22

(latest Tevatron updated combination – RunI data)(latest Tevatron updated combination – RunI data) mmtt=(175 =(175 17 17 (stat) (stat) 8 8 (syst)(syst)) GeV/c) GeV/c22

(CDF di-leptons – RunII data)(CDF di-leptons – RunII data) mmtt=(178=(178+13+13

-9-9 (stat) (stat) 7 7 (syst)(syst)) GeV/c) GeV/c22

(CDF lepton+jets – RunII data)(CDF lepton+jets – RunII data)

Matter of statistics (also for the main systematics) and optimized use of the Matter of statistics (also for the main systematics) and optimized use of the available information. Each experiment expects 500 b-tagged tt l+jets events/fb available information. Each experiment expects 500 b-tagged tt l+jets events/fb Mtop ~ 2-3 GeV/cMtop ~ 2-3 GeV/c22 for the Tevatron combined (2-4/fb) for the Tevatron combined (2-4/fb)

mmt t 2.5 GeV ; 2.5 GeV ; mmW W 30 MeV 30 MeV mmHH/m/mH H 35% 35%

Near future of Mtop

In 2009 (if upgrade is respected) from Tevatron: Mtop = 1.5 GeV !!

1 expectations for top quark physics in atlas at lhc clara troncon on behalf of the atlas...

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