The Truth The Top Quark is Hiding

THE TRUTH THE TOP QUARK IS

HIDING

Andrew Ivanov University of California, Davis

Fermilab Joint Experimental – Theoretical Seminar December 05, 2008

SEARCHES FOR NEW PHYSICS IN THE TOP QUARK SECTOR AT CDF

Andrew Ivanov University of California, Davis

Fermilab Joint Experimental – Theoretical Seminar December 05, 2008

A. Ivanov, UC Davis 3

MainInjector

Tevatron Ring ( ~4 miles)

DØBooster

Chicago

Tevatron Accelerator Complex

pp collisions at √s = 1.96 TeV

~ 4 fb-1 recordedExpect to collect

6 fb-1 by the end of 2009 ( 8 fb-1 by the end of 2010 )

CDF

CDF Integrated Luminosity

12/05/2008

A. Ivanov, UC Davis 412/05/2008

Fundamental Building Blocks of Matter



I.I. Rabi (1936)



• Top Quark ≅ Truth Quark(Fermilab, 1995)

• Mass ~ 175 GeV• Extraordinarily large!

• similar to a gold nucleus!

• ~40 times heavier than its partner- the bottom quark

• ~ 350, 000 times heavier

than electron!

• The Truth is heavy!



• Top Quark ≅ Truth Quark(Fermilab, 1995)

• Mass ~ 175 GeV• Extraordinarily large!

• similar to a gold nucleus!

• ~40 times heavier than its partner- the bottom quark

• ~ 350, 000 times heavier

than electron!

• The Truth is heavy!

Why is top so heavy ?


Facing the Truth

``Believe those who are seeking the truth; doubt those who find

it.” - Andre Gide


Top Production and Decay

BR( t-> Wb) ≈100%



BR( t-> Wb) ≈100%



BR( t-> Wb) ≈100%

Highest StatisticsDominant

BackgroundW+jets, S:B ≈ 1:1

Cleanest channelHigh S:B ≈ 3:1Backgrounds:

W/Z + jets


Grasping the TruthTop Quark Physics at Tevatron

tt Cross Section

pp

t

t

b

b

W+

W-

e+ e

d

u



tt Cross Section

pp

t

t

b

b

W+

W-

e+ e

d

u

Production MechanismForward-Backward

Asymmetry

tt Cross Section



tt Cross Section

pp

t

t

b

b

W+

W-

e+ e

d

u


Asymmetry

Top Mass, Width/Lifetime,Charge

tt Cross Section



tt Cross Section

pp

t

t

b

b

W+

W-

e+ e

d

u


Asymmetry


Spin Correlations

tt Cross Section



tt Cross Section

pp

t

t

b

b

W+

W-

e+ e

d

u


Asymmetry


Spin Correlations

Branching Ratio

tt Cross Section



tt Cross Section

pp

t

t

b

b

W+

W-

e+ e

d

u


Asymmetry


Spin Correlations

Branching Ratio

W helicity

tt Cross Section



tt Cross Section

pp

t

t

b

b

W+

W-

e+ e

d

u


Asymmetry


Spin Correlations

Branching Ratio

FCNC decays?

Z?

c?W helicity

tt Cross Section



tt Cross Section

pp

t

t

b

b

W+

W-

e+ e

d

u


Asymmetry


Spin Correlations

Branching Ratio

FCNC decays?

Z?

c?W helicity

ChargedHiggs

H- ?

tt Cross Section

12/05/2008

Top Quark Properties Measurements

top < 12.7 GeV at 95%CL(theory: top = 1.5 GeV )

ctop < 52.5 m at 95%CLtheory: top = 5 x 10-24 s )

Q=-4/3 excluded at 87% CL

(ggtt)/(pptt) = 0.07 ± 0.16(NLO: gluon~15%, quark~85%)

BR(t->Zq) < 10.6 % at 95% CL(SM: BR(t->Zq) ~ 10-14 )

Top Width Top Lifetime Top Charge

F0 = 0.65 ± 0.10(stat) ± 0.06(syst)F+ < 0.12 at 95% CL

(SM: F0 = 0.70 & F+ = 0.0)

Gluon Fraction FCNC Decays W Helicity

20

12/05/2008

Top Quark Properties Measurements

top < 12.7 GeV at 95%CL(theory: top = 1.5 GeV )

ctop < 52.5 m at 95%CLtheory: top = 5 x 10-24 s )

Q=-4/3 excluded at 87% CL

(ggtt)/(pptt) = 0.07 ± 0.16(NLO: gluon~15%, quark~85%)

BR(t->Zq) < 10.6 % at 95% CL(SM: BR(t->Zq) ~ 10-14 )

Top Width Top Lifetime Top Charge

F0 = 0.65 ± 0.10(stat) ± 0.06(syst)F+ < 0.12 at 95% CL

(SM: F0 = 0.70 & F+ = 0.0)

Gluon Fraction FCNC Decays W Helicity

About a quarter of CDF physics results presented at ICHEP08 are on properties of the top

quark

Results are mostly consistent with the Standard Model


New Physics Searches

Rresonant O

Production Mechanism

Intrinsic Property of Top Top Decay

e.g. Topcolor-Assisted Technicolor C.Hill, PRL B345, 483 (1995)Hill and Parke, PRD 49, 4454

(1994)

Resonance Top Charge Charged Higgs

Exotic quark with Q= -4/3 D. Chang, W. Chang and E. Ma, PRD 59 (1999) 091503PRD 61 (2000) 037301

Appears in SUSY and GUT modelsWithin MSSM for low tanb t-> H+b with enhanced branching ratio and subsequent decay H+->cs

_


New physics admixture in the sample of tops?

t’

``The pure and simple truth is rarely pure and never simple” - Oscar Wilde


Fourth Generation

• Possible 4-th generation quark with mass of few hundreds GeV

• Consistent with EWK data

• Oblique corrections drive Higgs Mass to ~ 500 GeV

G. Kribs, T. Plehn, M. Spannowsky, T. Taithep-ph/0706.3718


Fourth Generation

• Almost degenerate b´ and t´ masses:

• M(t´) - M(b´) < M(W)• Decays as top! • t´ -> Wb

G. Kribs, T. Plehn, M. Spannowsky, T. Taithep-ph/0706.3718

• Discrepancy with the SM?!• FB - b-quark forward-

backward asymmetry ~ 2.6 away (LEP)

• As a result: • sinw,lep is ~ 3.3 away

from sinw,had • Assumptions on mistakes

in the LEP measurements Underestimated

systematic uncertainty Systematical shift in the

measured valueare not satisfactory

Electroweak Precision Data

12/05/2008


Higgs = 84 +34-26 GeV/c2

Indirect Bounds on Higgs

12/05/2008

Higgs Mass FitFits to

leptonic data +AbFB +Ac

FB

M. Chanowitz, PRL 97 (2001) 231802

12/05/2008

Higgs Mass FitFits to

leptonic data +AbFB +Ac

FB

M. Chanowitz, PRL 97 (2001) 231802

95%C.L.

29


Beautiful Mirror Quarks• New physics in Z->bb? Different coupling of the b-quark to Z? • D. Choudhury, T. Tait C. Wagner, PRD 65 (2002) 053002• Mirror quarks of b-quarks improve the fit • Two scenarios: with and without top mirror quarks

Perfect for Tevatron searches Might have to wait for LHC

Standard Mirrors

Top-lessMirrors


Search Using 200 pb-1


Reconstructing the TruthTop Event Reconstruction

pp

t

t

b

b

W+

W-

e+ e

d

u

m(jj) = mW

m(l ) = mW

m (jjb) = m(l b)


Top Event Reconstruction

pp

t

t

b

b

W+

W-

e+ e

d

u

m(jj) = mW

m(l ) = mW

m (jjb) = m(l b)

• Jet combinatorics: • 12 possibilities

• Form 2

• Select configuration with lowest 2 jet-parton assignment

• Reconstruct mtop


Variables of Interest

• Quasi model-independent variables retain sensitivity to other possible beyond SM events

• Perform a 2-dim binned Likelihood Fit• Scan Likelihood as a function of t´ cross section• Include systematic effects as nuisance parameters• Maximize Likelihood with respect to all them - profiling method

HT MrecoHTMreco


Search Results Using 760 pb-1

mt’> 256 GeV at 95%CL

CDF, PRL 100 (2008) 161803


Data Fit for mt´ =350 / 400 GeV


Data Fit for mt´ =350 / 400 GeV

t’ candidates ?!


CDF Event Display


Search Results Using 2.8 fb-1

mt’> 311 GeV at 95% C.L.


Top Mass Measurements

• Dilepton Channel:

Mt = 173.4 ± 2.5 (stat) ± 1.3(syst)Mt = 164.5 ± 3.9 (stat) ± 3.9 (syst)

• Lepton +Jets Channel:



Tevatron Combination:

7% chance that LJ and DIL results more discrepant than observed

Fermilab-TM-2380-E, TEVEWWG/top 2007/01



Stop mass below the mass of the top quark?

Can the top data have an admixture of

stop quarks?


Supersymmetry

• One of the first and well motivated theories beyond the SM

• Pros:- Naturally cures the hierarchy problem

• Cons:- Doubles the number of elementary particles

• SUSY must be broken


Why Supersymmetry?

Electroweak Baryogenesis


Why Supersymmetry?

Dark Matter



Why Supersymmetry?


Why Supersymmetry?

REPRODUCIBILITY


Why Supersymmetry?

ANYTHING THAT IS NOT FORBIDDEN IS MANDATORY


Why Supersymmetry?

ANYTHING THAT IS NOT FORBIDDEN IS MANDATORY

df=√2ay (boson fermion )dy=√2aF+i√2adf(fermion boson )

-


What is so special about stop?

• t1 -> b 1+ -> b 1

0 W+(*) -> b 10 l

BR ≈ 100%

~

~

~ ~ ~ ~



• t1 -> b 1+ -> b 1

0 W+(*) -> b 10 l

BR ≈ 100%• Theoretical Assumptions:

1)10 is the LSP

– Supported by cosmological observations: dark matter relic density (WMAP)

~

~

~ ~ ~ ~



• t1 -> b 1+ -> b 1

0 W+(*) -> b 10 l


1)10 is the LSP


2)m(t1) ≤ mt

~

~

~ ~ ~ ~



• t1 -> b 1+ -> b 1

0 W+(*) -> b 10 l


1)10 is the LSP


2)m(t1) ≤ mt

~

~


C. Balazs, M. Carena, C. WagnerPRD 70 (2004) 015007

~ ~ ~ ~



• t1 -> b 1+ -> b 1

0 W+(*) -> b 10 l


1)10 is the LSP


2)m(t1) ≤ mt

3)m(1+) ≤ m(t1) – mb, ; q, l , are

heavy

~

~


C. Balazs, M. Carena, C. WagnerPRD 70 (2004) 015007

Mass generation ~ ~ ~ ~


Stop Under Top Event Reconstruction

pp

t1

t1

b

bW-

e+ e

d

u

~

1+

10

1-

10

~

W+



pp

t1

t1

b

bW-

e+ e

d

um(jj) = mW

m(l ) = mW

m (jjb) ≠ m(l b)

~

1+

10

1-

10

~

W+



pp

t1

t1

b

bW-

e+ e

d

um(jj) = mW

m(l ) = mW

m (jjb) ≠ m(l b)m (jjb1

0) = m(l b1

0)

~

1+

10

1-

10

~

W+



pp

t1

t1

b

bW-

e+ e

d

um(jj) = mW

m(l ) = mW

m (jjb) ≠ m(l b)m (jjb1

0) = m(l b1

0)

~

1+

10

1-

10

~

W+

In the lepton + jets channel stop signal is hidden in

backgrounds to top


Top Dilepton Event Reconstruction

pp

t

t

b

bW-

e+

e

W+

e-

e

m(l 22) = mW

1 + 2 ) T = ET

E

1

2

m(l 11) = mW


Stop Under Top Dilepton Event Reconstruction

pp

t1

t1

b

bW-

e+ e

~

1+

10

1-

10

~

W+

e-

e

m(l 1110,1) =

m1+

m(l 2210,1) =

m1+


Would Admixture of Stops Affect Top Mass Measurements?

Yes!Would Bias Top

Dilepton Masstowards a value lower

by a few GeV. Exactly what we see in

Tevatron data!


Would Admixture of Stops Affect Top Mass Measurements?

Yes!Would Bias Top

Dilepton Masstowards a value lower

by a few GeV. Exactly what we see in

Tevatron data!

If m(1 ±) - m(10) < m(W)

Dilepton branching ratio can be enhanceddue to other SUSY particles off-shell:


Stop Dilepton Reconstruction

pp

t1

t1

b

bW-

e+ e

~

1+

10

1-

10

~

W+

e-

e

m(l 1110,1) =

m1+

m(l 2210,1) =

m1+

m(b1-,1) =

m(b1+,2)

• Four invisible particles

• W is off-shell • cannot use mW

constraint

• m(1+) is unknown



pp

t1

t1

b

bW-

e+ e

~

1+

10

1-

10

~

W+

e-

e

m(l 1110,1) =

m1+

m(l 2210,1) =

m1+

m(b1-,1) =

m(b1+,2)



pp

t1

t1

b

bW-

e+ e

~

1+

10

1-

10

~

W+

e-

e

m(l 1110,1) =

m1+

m(l 2210,1) =

m1+

m(b1-,1) =

m(b1+,2)

• For masses m(10) ~ 46 – 90 GeV/c2

It is sufficient to create “pseudo-particle” with wide width

m(10)

= 10GeV/c2

75 GeV/c2

10)1,T + 1

0)2,T = ET

- Similar to top dilepton event



pp

t1

t1

b

bW-

e+ e

~

1+

10

1-

10

~

W+

e-

e

m(l 1110,1) =

m1+

m(l 2210,1) =

m1+

m(b1-,1) =

m(b1+,2)

What about m(1+) ?

Make m(1+) a parameter

in the fit, and reconstruct stop mass for various assumed values of m(1

+) e.g. 105, 125 GeV/c2



pp

t1

t1

b

bW-

e+ e

~

1+

10

1-

10

~

W+

e-

e

m(l 1110,1) =

m1+

m(l 2210,1) =

m1+

m(b1-,1) =

m(b1+,2)



pp

t1

t1

b

bW-

e+ e

~

1+

10

1-

10

~

W+

e-

e

m(l 1110,1) =

m1+

m(l 2210,1) =

m1+

m(b1-,1) =

m(b1+,2)

Mstop = 135 GeVM+= 105 GeVM0= 45 GeV


Can we see stop?

7412/05/2008

Handling Systematics: Template Morphing

E.g. Jet Energy Scale (JES): Obtain JES +-1shifted templates by shifting JES upward and downward Include the shape transformation due to variation of JES into the fit Horizontal morphing is an interpolation between two cumulative

distribution functions (C.D.F.) The green C.D.F. curve is the 75% interpolation between the blue

and red C.D.F. curves.

A. Read, Nucl. Instrum. Meth. A425:357-360 (1999)


Template Morphing in Action


Top Dilepton Mass Results Using 1.8 fb-1


Results


Limits

First direct limits on masses of SUSY particles in this stop decay chain


Conclusion Remarks

• Top Mass discrepancy between different channels vanished with more data

• Stop admixture has not been an origin of earlier discrepancies

• Yet it remains a possibility based on theoretical arguments and might still remain hidden in Tevatron data


Summary

• Top quark remains to be mysterious particle

• No significant deviations from SM in measurements of the top quark properties have been observed

• Yet some potentially interesting effects remain

• The truth about Nature might still be hiding in the top quark/Tevatron data

• With more Tevatron data the chance for discovery remains a possibility

THANK YOU !

12/05/2008 82

BACKUP SLIDES

12/05/2008 83


CDF Event Display



mt’> 311 GeV at 95%CL


Top Killer

A few topological cuts to reduce tt events

Stop TopTOP STOP

Cut this area Keep stop


Tevatron Limits on t1-> c10

~


Tevatron Limits on t1-> b l ~

~

The Truth The Top Quark is Hiding

Documents

Transcript of The Truth The Top Quark is Hiding