The top quark yesterday and today
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The Top Quark Yesterday and Today. Hugh Montgomery Jefferson Lab IRFU-CEA Saclay February 4, 2010. Outline. Why do we need the top quark? A virtual life Observation of the Top Quark Properties of the Top Quark Electroweak Coupling of the Top Quark The Top Quark and the Future.

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The top quark yesterday and today

The Top Quark Yesterday and Today

Hugh Montgomery

Jefferson Lab

IRFU-CEA Saclay

February 4, 2010


Outline

Outline

Why do we need the top quark?

A virtual life

Observation of the Top Quark

Properties of the Top Quark

Electroweak Coupling of the Top Quark

The Top Quark and the Future


Elementary particle physics

Elementary Particle Physics


Elementary particle physics1

Elementary Particle Physics

Fermicentric Dates

Major Discoveries

  • b quark1977

  • t quark1995

  • nt(tau neutrino)2000

    Critical measurements

  • t and W mass1998

  • proton structure1984-95 using neutrinos and muons

  • QCD at highest 1988-now energies


Upsilon discovery 1977

Upsilon Discovery- 1977

bound state of bottom quarks


The virtual life of the top quark

The Virtual Life of the Top Quark

10


Premature single top production

Premature Single Top Production

Schwienhorst – Fermilab W&C 4/1/2005


An ephemeral existence

An ephemeral existence

UA1 at the SppS

1984:

–Using isolated high transverse momentum lepton

–2 or 3 hadron jets

–Observed 5 events (e+ >=2 jets); 4 events (μ+ >=2 jets)

–Expected background: 0.2 events

•fake leptons dominate

•bb & cc production negligible

–Conclude: results consistent with M top = 40 ±10 GeV

1988:

–x6 the data

– much better understanding of backgrounds

– M top > 44

Yagil – Top Turns Ten


For a top mass less than the w mass ua2 88 89 was competitive with cdf

For a top mass less than the W mass UA2 (88/89) was competitive with CDF

Yagil – Top Turns Ten


Mass predictions and limits

Mass Predictions and Limits

Quigg, Langacker


Fermilab antiprotons

Fermilab Antiprotons


Tevatron run i and top

57pb

19pb

Tevatron Run I and Top

Dec 94

Aug 93

Yagil – Top Turns Ten


Cdf the experiment

CDF - The Experiment


Urgency

D0

CDF

Urgency

Glenzinski – Top Turns Ten


Dzero

DZero


A first hint for cdf

A First Hint for CDF

Yagil – Top Turns Ten


A dzero top quark

A DZero Top Quark?


Profile of the top quark

Profile of the Top Quark

Grannis– The Antitop Quark at the Antiproton celebration, LBL


Top production and decay

Top Production and decay

DIL - both W decay to leptons

Low rate, Very clean

SVX - one of the b-jets is identified using a displaced vertex tag

SVX detector

SLT - one of the b-jets is identified using a leptonic decay product

lepton I.D. in jets

Yagil – Top Turns Ten


Dilepton observations 1995

Dilepton Observations 1995

Grannis– The Antitop Quark at the Antiproton celebration, LBL


Single lepton jets

Single Lepton & Jets

Grannis– The Antitop Quark at the Antiproton celebration, LBL


Discovery observation

Discovery : Observation

Grannis– The Antitop Quark at the Antiproton celebration, LBL


The top quark yesterday and today

List of Institutions on Dzero at time of discovery

(Grannis), Hadley – Top Turns Ten


The top quark yesterday and today

Dzero Author List

Abachi to Zylberstejn

Thanks to all

(Grannis), Hadley – Top Turns Ten


Top mass

Top Mass


Constraints observables

Constraints/Observables

  • 18 fermion 3-vector components

  • Use constraints

    • W mass (twice) (2)

    • Mass of top = mass of antitop (1)

    • Assume mass for top

    • Fit using measurement errors

  • Measure 1 lepton(3) and 4 jets (12) and Missing Transverse Energy (2)

    • 20 constraints plus measurements (20-18 2C)

  • Measure 2 leptons(6) and 2 jets (6) and Missing Transverse Energy (2)

    • 17 constraints plus measurements (17-18 -1C)

  • Further constraints

    • The parton distributions (poor man’s beam energy)

    • Internal characteristics

    • Full matrix element


Top mass methodologies

Top Mass: Methodologies

  • Choose any characteristic of the event which is related to the top mass

    • Lepton transverse momentum

    • B quark decay length

    • Mass reconstructed by constrained fit

      • To lepton plus jets events (2C)

        • using just kinematics

        • Using full matrix element

        • Reducing combinations with b tagging

      • To dilepton events (<~0C!!!)

        • using all the approaches above

      • To All jets events

        • Using all the different approaches above

    • WITH (IN)Efficiencies properly treated!!

      • Lots of MC studies

    • WITH BACKGROUNDS properly treated!!


The mass of the top quark

The Mass of the Top Quark

CDF 1994

CDF measured:

1994 Mtop = 174 +- 10 +- 13 GeV

1995 Mtop = 176 +- 8 +- 10 GeV

Yagil – Top Turns Ten


Top mass1

Top Mass

Grannis– The Antitop Quark at the Antiproton celebration, LBL


D0 run i full matrix element

D0 Run I – Full Matrix Element

For each event estimate probability for a top mass value using all measured quantities compared to distribution of t-tbar production matrix element.

(Need to integrate over measurement resolutions)


Contemporary top mass

Contemporary Top Mass

Tevatron (Winter 09):

mt=173.1 ± 0.6 (stat) ± 1.1 (syst) GeV

mt=173.1 ± 1.3 (stat+syst) GeV

CDF (4.3 fb-1):

mt(l+j)=172.6±0.9(stat)±0.7(JES) ±1.1(syst)GeV

Single Experiment Uncertainty

~1 GeV!!!!

FlorenciaCanelli, LP2009


Implications of the top quark mass

Implications of the Top Quark Mass

The total width of the top quark is 1- 1.5 GeV

( proportional to m3 )

The top quark decays in 0.5 * 10-24 seconds

Before it can form a hadron

No top mesons

No toponium

No hadronisation

Hadronisation does not modify the spin orientation

The observed mass is that of the quark

The top quark is our only bare quark!


Luminosity helps

Luminosity Helps

FlorenciaCanelli, LP2009


Top quark pair production cross section

Top Quark Pair Production Cross Section

Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift


Top quark pair production cross section1

Top Quark Pair Production Cross Section

6% precision!

~ 6% Precision

FlorenciaCanelli, LP2009


Ttbar production spectra

ttbar production spectra

Grannis– The Antitop Quark at the Antiproton celebration, LBL


Ttbar production

ttbar Production


Single top production

Single Top Production

Schwienhorst – Fermilab W&C 4/1/2005


Single top production1

Single Top Production

Tevatron (3.2 fb-1):

st=2.76 +0.58 -0.47 (stat+syst) pb

Tevatron (3.2 fb-1), PRD66 054024, 2002:

|Vtb|=0.91 ± 0.08 (stat+syst)

FlorenciaCanelli, LP2009


Top quark properties

Top Quark Properties


Top quark properties1

Top Quark Properties

FlorenciaCanelli, LP2009


Top quark decays

Top Quark Decays

R = B(tWb)/B(tWq)

Related to Vtb

Determined from the relative numbers of 0, 1 and, 2 b quark tags

D0 Result (CDF similar)

R = 1.03+/-0.19/0.17

Vtb >~ 0.8

Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift

Buescher- D0 Report to PAC, December 2005


Top quark decays1

Top Quark Decays

t  H+b?

Different possible decays of the H+

Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift


W helicity in top decay

W-Helicity in top Decay

Correlations between the lepton and b jet direction in the W rest frame.

lepton pT spectrum depends on W helicity

Effective mass of lepton and b jet

Fit to full matrix element

κ = N(↑↑) + N(↓↓) − N(↑↓) − N(↑↓)

N(↑↑) + N(↓↓) + N(↑↓) + N(↑↓)

Grannis– The Antitop Quark at the Antiproton celebration, LBL

Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift


Top antitop spin correlations

Top-antitop spin correlations

κ = N(↑↑) + N(↓↓) − N(↑↓) − N(↑↓)SM predicts κ = 0.78

N(↑↑) + N(↓↓) + N(↑↓) + N(↑↓)

D0 (4 fb-1): κ =-0.17 +0.64 -0.53

CDF (2.8 fb-1): κ =0.32 +0.55-0.78

FlorenciaCanelli, LP2009


The charge of the top quark

The Charge of the top Quark

Use jet charge algorithms to attempt to determine the b and bbar jets.

Use event fit to make associations between the W and the b jet

Construct a top charge: compare with the MC of SM and Exotic

D0 Analysis

Data favor charge 2/3, excluding 4/3 with 93.7% cl.

Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift

Buescher- D0 Report to PAC, December 2005


Top quark spin

Top Quark Spin

Top and anti-top spins are correlated

Analysis looks at relative orientation of the leptons in the top-antitop decays

Correct spin ½ favored

Quadt– Top Quark Physics at Hadron Colliders- Habilitationschrift

Buescher- D0 Report to PAC, December 2005


Search for cpt violation

Search for CPT Violation

Release constraint on mt = mtbar, measured in lepton + jets events using

matrix element technique

D0 (1 fb-1): Dmt=3.8 ± 3.7 GeV


Electroweak relationships

Electroweak Relationships

  • The top contributes as mt2 to the boson masses

  • The Higgs contributes as ln mh2 to the boson masses

http://lepewwg.web.cern.ch/LEPEWWG/


Electroweak parameters

Electroweak Parameters

FlorenciaCanelli, LP2009


Future promises

Future Promises

Theory

SUSY see-saw mechanisms suggest mstop lowest of SUSY masses

Higgs as a top condensate composite

Tevatron

DM <~ 1 GeV

Constraints on the Higgs

Anomalies

LHC

Signals pointing to EWSB mechanism

Vtb from single top production

Higgs – top coupling

ttg, ttZ couplings

Rare decays

ILC

DM <~ 20 MeV


Future promises1

Future Promises

Standard Model Electroweak Relations

MW=(1/2)gv , MZ = (1/2) sqrt(g2+g’2)v

Mf = Lf v/sqrt(2)

Arithmetic

v = 246 GeV, v/sqrt(2) = 174 GeV

Mt ~ 173 GeV

Lt =1!!!!

Just a coincidence???


Summary

Summary

The top quark was conceived more than thirty years ago.

Some of us are surprised that it is already fifteen years since we helped at its birth.

Even as born it was a giant, helping us to target the Higgs.

Top is still a big baby.

Maybe, it is very close to the Higgs.

Its next ten years promise further greatness.


Acknowledgements

Acknowledgements

This talk depended almost 100% on the work of others:

The colleagues on CDF and D0 with whom I shared the experience of experimental discovery.

Juan Estrada FNAL W&C – Matrix Element work

The speakers at Top Turns Ten, October 2005: Jim Cochran, Bogdan Dobrescu, Doug Glenzinski, Nick Hadley, Paul Langacker, Aldo Menzione, MeenakshiNarain and AviYagil.

Paul Grannis: Talk at the celebration for the AntiProton.

ArnulfQuadt, whose Habilitation thesis provided one re-education on the subject and some of the figures for the talk.

FlorenciaCanelli whose summary talk at LP2009 I used for some recent plots

Giorgio Chiarelli, Rencontres de Blois, 2009

The beautiful work done by CDF and D0 collaborations during Run II when I have been an anxious spectator.

The Tevatron


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