the top quark beyond the sm at atlas granada 29 th june 2006 antónio onofre lip / ucp universidad...

The Top Quark Beyond The Top Quark Beyond the SM at ATLASthe SM at ATLAS

Granada 29Granada 29thth June 2006 June 2006

António António OnofreOnofreLIP / UCPLIP / UCP

Universidad de GranadaUniversidad de GranadaDepartamento de Física Departamento de Física Teórica y del Cosmos Teórica y del Cosmos

OutlineOutlineI)I) What do we know about What do we know about

the the top quark?top quark?

II)II) The top quark at ATLAS The top quark at ATLAS

III)III) Conclusions Conclusions

GranadaGranada, 29, 29thth June 2006 June 2006

I) What do we know about the top I) What do we know about the top quark?quark?

Nν = 2.9841±0.0083

The top quark completes the 3 family The top quark completes the 3 family structure of the SMstructure of the SM

It has spin=1/2,It has spin=1/2, Charge=+2/3,Charge=+2/3, It´s the weak-isospin partner of the b-It´s the weak-isospin partner of the b-

quark,quark, =1.42GeV (including m=1.42GeV (including mbb,M,MWW,,ss,EW corr.),EW corr.) It’s a massive particle (special role in It’s a massive particle (special role in

SM?)SM?)

From the SM we know From the SM we know that:that:

QCD-1=(100MeV)-1=10-23s

Mt => t<10-23sHadronization time

NO top hadrons


From From ee++e, ee, e±±p and ppp and pp Colliders we have top Colliders we have top quark dataquark data

--

LEPLEPALEPH, DELPHI,ALEPH, DELPHI,

OPAL and L3OPAL and L3

(e(e++ee- -

Collider)Collider)

HERAHERAH1 and ZEUS H1 and ZEUS

(e(e±±p Collider)p Collider)

TEVATRONTEVATROND0 and CDFD0 and CDF

(pp Collider)(pp Collider)--



Beyond SM

Beyond SM

SM+Beyond

The TEVATRONThe TEVATRON

The present experimental knowledge on top quark physics is dominated by the TEVATRON data

•Run I (1992-1996)s = 1.8 TeVDiscover top quark in 1995Integrated luminosity 120pb-1

•Run II (2001-present)s = 1.96 TeVTotal Int.Luminosity Delivered: ~1.5fb-

1/expRecorded ~1.2fb-1/expFutur: ~2fb-1 (by 2006) ~4fb-1 (by 2007) ~8fb-1 (by 2009)•2 multi-purpose detectorsD and CDF



A) The top mass (TEVATRON,LEP,SLD)A) The top mass (TEVATRON,LEP,SLD) I) What do we know about the top I) What do we know about the top quark?quark?


measuredinferred

A) The top mass at RUN II (TEVATRON)A) The top mass at RUN II (TEVATRON)Summary of Top Mass Results


GranadaGranada, 29, 29thth June 2006 June 2006 mmtt=172.5±2.3 GeV/c=172.5±2.3 GeV/c22

http://www-cdf.fnal.gov/physics/new/top/summaryplots/tevbest.gif

q

q

t

t ~85%

t

t

g

g~15%

Diagrams: Dependence with Energy:

B) The pp tt cross section (TEVATRON) B) The pp tt cross section (TEVATRON)

(pp tt)@NLL=6.7pb (15% uncertainty) at Mt=175GeV



Top quarks are rare events: 1 in 10Top quarks are rare events: 1 in 101010 events !!!events !!!

http://www-cdf.fnal.gov/physics/new/top/summaryplots/combo_roots_750pb.gif

CDF Run 2 Preliminary:

D0 RUN 2 Preliminary:

B) The pp tt cross section (TEVATRON) B) The pp tt cross section (TEVATRON) I) What do we know about the top I) What do we know about the top quark?quark?


http://www-cdf.fnal.gov/physics/new/top/summaryplots/combo_xs_750pb.gif

http://www-d0.fnal.gov/Run2Physics/top/top_public_web_pages/plots/dzero_ttbar_xsec_summary_spring06.eps

C) The t bW decay and W polarizationC) The t bW decay and W polarization

t

W0 Longitudinal fraction F0

W

b

+1/2

+1/2

0

W- Left-Handed fraction F-

tb

W

+1/2

-1/2

+1

W+ Right-Handed fraction F+

tW

b

+1/2+1

-1/2V-A SUPPRESSED

W boson has three helicity states:

“Left-handed”, “Longitudinal”, “Right-handed”

Top quark decay is the most significant source of Longitudinal Ws.



By measuring the fraction of longitudinal Ws we are:

Testing a Standard Model prediction: F0=0.7 F-=0.3 Probing the structure of the tWb vertex

C) The t bW decay and W polarizationC) The t bW decay and W polarization



W(cos*)=F 3 (1-cos*)2 + F 3 (1-cos2*) + F 3 (1+cos*)2 848

- +0

http://www-cdf.fnal.gov/physics/new/top/2006/tprop/whelicity_CosTheta/plots/data_hel_raw.gif

D) Top Rare decaysD) Top Rare decays The top quark almost always decays to a b quark, B(tWb)~1 Most of the SM rare decays of the top are really rare

B(tWs)<0.18%, B(tWd)<0.02%

The Ratio of Events with b-tagged and no b-tagged jets is: R=B(tWb)/B(tWq) = |Vtb|2 / (|Vtd|2 + |Vts|2 + |Vtb|2) =99.8%

FCNC Decays: B(t c) +B(t u)<3.2% at 95% CLB(t Zc) +B(t Zu)<33% at 95% CL



A) The Most Exciting Discoveries are the Unexpected OnesA) The Most Exciting Discoveries are the Unexpected Ones Unfortunately it Seems Difficult To Predict the Unexpected…Unfortunately it Seems Difficult To Predict the Unexpected…

Why Going Beyond the SM?Why Going Beyond the SM?

B) Physics Beyond the SM Required for UnificationB) Physics Beyond the SM Required for Unification SuperSymetry at TeV scale modifies evolution of couplingsSuperSymetry at TeV scale modifies evolution of couplings Unification and Agreement with DataUnification and Agreement with Data


II) The top quark at ATLASII) The top quark at ATLAS

C) New Physics is also a test of the SM…C) New Physics is also a test of the SM… It is mandatory to measure the top quark quantum numbersIt is mandatory to measure the top quark quantum numbers

ATLAS at CERNATLAS at CERN

Geneve Airport

LHC

CERN

SPS Accelerator

CERN (Prevessin) 27 km

ATLAS, CMS, LHCb e ALICE

20 Member States + USA, Canada, Japan, Russia, China, India, ...



• Proton-Proton Collisions Ecm = 7000 + 7000 GeV• 800 million collisions/s• The biggest cryogenic system in

the world (1.8K, superfluide helium)

• 27 km of magnets with B=8T

II) The top quark at ATLASII) The top quark at ATLASATLAS at CERNATLAS at CERN


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

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)

pp tt bbWpp tt bbW++WW-- (833pb) (833pb)

• 1 Lepton pT>20 GeV, |η|<2.5• ET>20 GeV• ≥ 4 jets ET>40 GeV, |η|<2.5• ≥ 2 b-tags

Signal: tt bbqq´Signal: tt bbqq´llll++ (l=e,(l=e,))



A) The top mass at ATLASA) The top mass at ATLAS

proton beam proton beam

W bt

qq|

Jet

Jet Jet (b)

Jet (b)

Semileptonic TopologySemileptonic Topology

neutrino

e,

MMtt(had)(had)MMWW(had)(had)

Selected 87000 events for 10fbSelected 87000 events for 10fb-1-1 (S/B~78) (S/B~78)

Most Important Systematic Errors: Most Important Systematic Errors: Energy Jet Calibration Energy Jet Calibration FSR FSR

Systematic Errors:Systematic Errors:

SN-ATLAS-2004-040

Tot(sys) = 1.3 GeVTot(stat) = 0.1 GeV



A) The top mass at ATLASA) The top mass at ATLAS



B) Anomalous Couplings in the tB) Anomalous Couplings in the tbW decaybW decay

Angular Asymmetries:Angular Asymmetries: AAFBFB, , AA++ andand AA--

AAFBFBAA++

AA--

cos(cos(ll*)*)

AAFB FB [t=0] [t=0] AA±± [t= (2[t= (22/32/3-1)]-1)]±±



MMt-lept-lepMMt-hadt-had

LogLog1010(L(Lss//LLBB))Sig.Sig.

BacKBacK..

L=10fbL=10fb-1-1

Pre-Selection (Probabilistic):Pre-Selection (Probabilistic): 1 lepton pT>25GeV,|1 lepton pT>25GeV,||<2.5|<2.5 4 jets, pT>20GeV4 jets, pT>20GeV,|,||<2.5|<2.5 2 b-tag jets2 b-tag jets Missing pTMissing pT>20GeV>20GeVFinal Selection: Final Selection: LogLog1010(L(Lss/L/LBB) > -0.2) > -0.2




The measured Angular Distributions are affected by detector The measured Angular Distributions are affected by detector related effects (resolutions, triggers, selection criteria, etc.) related effects (resolutions, triggers, selection criteria, etc.)

To recover the “To recover the “TrueTrue” signal ” signal (S)(S) Angular Distributions, Angular Distributions, reference MC samples for signal reference MC samples for signal (S(Srefref)) and back. and back. (B(Brefref)) were were generated to estimate the expected Correction Function used to generated to estimate the expected Correction Function used to compensate for experimental effects (compensate for experimental effects (ffCC=G/S=G/Srefref););

The signal is extracted from “The signal is extracted from “DataData” ” (S(S00+B+B00)) by: by: S = S = (S(S0 0 + B+ B0 0 - B- Brefref) ) xx G/SG/Srefref





L=10fbL=10fb-1-1

SM (LO): SM (LO): AAFBFB = -0.2226= -0.2226AA++ = 0.5482= 0.5482AA-- = -0.8397= -0.8397

/A/AFBFB = 6.0%= 6.0%/A/A++ = 1.9%= 1.9%/A/A-- = 0.4%= 0.4%

Systematic Errors:Systematic Errors:




The dependence of AThe dependence of AFBFB on the Anomalous Couplingson the Anomalous Couplings

The b-quark mass must be taken into account The b-quark mass must be taken into account (differences up to 17% in g(differences up to 17% in gLL and 9% in V and 9% in VRR))



B) Anomalous Couplings in the tB) Anomalous Couplings in the tbW decaybW decay1) Anomalous Couplings with W 1) Anomalous Couplings with W polarization:polarization:

2) The helicity fractions are related to A2) The helicity fractions are related to AFBFB, A, A++ and and AA--::

SM(LOSM(LO):):

3) Best Results:3) Best Results:

(careful with definitions when comparing to (careful with definitions when comparing to TEVATRON)TEVATRON)




Best 1Best 1 Results: Results:

Working Going on…Working Going on…

C) Top Quark FCNC decays (tt events)C) Top Quark FCNC decays (tt events)

Highly Suppressed in the SM:Highly Suppressed in the SM:






Probabilistic Type Probabilistic Type of Analysis after Pre-of Analysis after Pre-selectionselection

Pre-Selection:Pre-Selection:




Specific Criteria:Specific Criteria:

A) ATLAS Sensitivity (5A) ATLAS Sensitivity (5):):

B) Absence of Signal (95% C.L.):B) Absence of Signal (95% C.L.):

C) Dominant Systematic Errors: MC) Dominant Systematic Errors: Mtt e e b-tagb-tag < < 20%20%




Combined Combined Plot:Plot:




Conclusions Conclusions

There is no doubt that colliders are doing There is no doubt that colliders are doing a Great Job up to now…a Great Job up to now…

Wait for the next data at the LHC...Wait for the next data at the LHC...

Many analysis are under preparation for Many analysis are under preparation for the LHC and a strong collaboration the LHC and a strong collaboration between Theoreticians and between Theoreticians and Experimentalists is necessaryExperimentalists is necessary

The Top Quark Physics is one of the best The Top Quark Physics is one of the best places to look for New Physics (at least it places to look for New Physics (at least it is there…)is there…)

The best way to access the The best way to access the top spin top spin is is to study de angular distribution of its to study de angular distribution of its decay products:decay products:

ii = analysing power of = analysing power of particle iparticle i Spin Correlations in pp tt:Spin Correlations in pp tt:



B) Top spin correlations (asymmetries)B) Top spin correlations (asymmetries)

X=l

X

X

SMC(LO)

C(NLO)0.3190.326

Double Differential Distributions:Double Differential Distributions:

Opening Angle Distributions:Opening Angle Distributions:



SMD(LO)

D(NLO)-0.217-0.237

SM Predictions:SM Predictions:

l+,t

l,q

t

q

l+,t

lqq

t

Asymmetries Definitions:Asymmetries Definitions:

B) Top spin correlations (asymmetries)B) Top spin correlations (asymmetries)

We have considered: We have considered: Alj , Ãlj , Aj



B) Top spin correlations B) Top spin correlations (asymmetries)(asymmetries)

Alj

Aj

Ãlj

L=10fbL=10fb-1-1



B) Top spin correlations (asymmetries)B) Top spin correlations (asymmetries)Systematic Errors Systematic Errors (probabilistic):(probabilistic):



E) Top Quark FCNC decays (Single top E) Top Quark FCNC decays (Single top Events)Events)

A) Diagrams For Single top A) Diagrams For Single top production:production:

B) Decays under study:B) Decays under study:

ee

A)A)

B)B)




A) ATLAS Sensitivity (5A) ATLAS Sensitivity (5):):

B) Absence of Signal (95% C.L.):B) Absence of Signal (95% C.L.):




New InteractionsNew InteractionsQuark Radius at Quark Radius at CollidersColliders

HERA (H1)HERA (H1) Results Interpreted in terms of ffqq(Q(Q22))

Result:Result: R<1.7x10 R<1.7x10--

1616cmcm

q-form factor:q-form factor:

dd/dQ/dQ2 2 = d= dSMSM/dQ/dQ2 2 x x ffqq(Q(Q22))

TevatronTevatron ((CDF, DY CDF, DY ee++ee--,,++--)) Result:Result: R<1.0x10R<1.0x10-16-16cmcm

ffqq(Q(Q22)=1-)=1- 1 1 <R<R22>Q>Q22

66

In SM (mIn SM (mtt=175GeV/c=175GeV/c22))BB((ttcc) ) ~ 5.2x10 5.2x10 -13 -13

BB((ttZZcc) ) ~ 1.5x10 1.5x10 -13 -13

SM extensions lead to large SM extensions lead to large enhancements:enhancements:1).1). 2HDM 2HDM ggijij (m (mqiqimmqjqj))2). k2). k, k, kZZ

CDF searched for: CDF searched for: ttc(u)c(u)and and ttZc(u)Zc(u)

BBttccBBttuu< 3,2%< 3,2%BBttccBBttuu< <

33%33%

CDF CDF kk22<<0.176 0.176

kk22ZZ<0.533<0.533 at at ==mmtt

At LEPAt LEP

kkZ are are

Anomalous CouplingsAnomalous Couplings

c(u)c(u)

tt

e-e-

e+e+ Z,Z, kk, k, kZZ

Top Quark and FCNCTop Quark and FCNC At eAt e++ee--, pp Colliders, pp Colliders

__

DELPHI, OPAL, L3, ALEPHDELPHI, OPAL, L3, ALEPHsearched at LEP for searched at LEP for ee++ee- - tc(u) tc(u) bWc(u) bWc(u)

Hadronic:Hadronic: WWqq´qq´ Leptonic:Leptonic: WWll±±

Top Quark and FCNCTop Quark and FCNC At eAt e++ee--, pp Colliders, pp Colliders

__

s(GeV)

Lumi.(pb- 1) Had. Lep.

95%(pb)

DELPHIOPAL

L3ALEPH

192- 202189189

189- 202

233172176411

YYYy

Y-yy

0.320.390.200.72

the top quark beyond the sm at atlas granada 29 th june 2006 antónio onofre lip / ucp universidad...

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