# Presentation: 211670

## Top Results from the Tevatron

***         *****Andrew Ivanov**
**    ****University of California, Davis**
**for the CDF and D0 Collaborations**

**Aspen Winter Conference****   **
**         ****February 13, 2006**

## Top Quark

- Not a surprising discovery: b-quark requires isospin partner, however ...

- Discovered in 1995 at Tevatron
- Youngest member of the quark family
- “Last brick” to the Standard Model

- A. Ivanov,   UC Davis

- Feb-13-2006

## Why is the top quark so special ...

**TOP**

- Unexpectedly huge mass
- Comparable to gold nucleus

** ****~****175 GeV**

- Decays before hadronizing
- Passes momentum and spin info to its decay products

- Special role in the dynamics of EWSB ?
- Serves as a probe of BSM physics

- A. Ivanov,   UC Davis

- Feb-13-2006

**Notes:**
Mass of order electroweak scale
May play a special role in the dynamics of EWSB
Serves as a powerful probe of physics beyond the SM

## Tevatron Collider

- Currently the world’s only top quark production machine
- Operating at world’s highest particle energy collisions
- Two multi-purpose detectors
- Run I (1992-1996)
-  √s = 1.8 TeV
- Integrated Lum ~110 pb-1
- Top Discovery!
- Run II (2001-present)
- √ s = 1.96 TeV
- 30% higher ttbar cross section

- A. Ivanov,   UC Davis

- Feb-13-2006

## Luminosity in Run 2

- Record initial Luminosity 1.8x1032 cm-2s-1
-       (11/10/2005)
- Expect 2.5x1032 cm-2s-1 next year
- On tape ~1.2 fb-1
- New results with up to Sep 2005 ( ~760 pb-1)
-      x7 of Run I  !
- Some of analyses presented here use up to Sep 2004 (~360 pb-1)

- A. Ivanov,   UC Davis

- Feb-13-2006

## Tevatron Detectors

- Inner Silicon Precision Tracking
- Tracking Chambers
- Solenoid
- EM and HAD calorimeters
- Muon Detectors

**All crucial**
** ****for top physics!**

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Quark Production

- ~85 %

- ~15%

- Within SM
- tt = 6.7 ±0.7 pb  @ mtop = 175 GeV
- Cacciari et al. JHEP 0404:068(2004)
- Kidonakis,Vogt PRD 68 114014(2003)
- One top pair every 1010 inelastic collisions
- Produced ~15000 top pairs so far

- 0.9

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Quark Decay

***t ************ Wb***
- Events classified by *W* decay
*“**Lepton [e,****] + jets” (30%)*
***tt ************ bl************bqq******′***
*“**Dilepton [e,****]” (5%)*
***tt ************ bl************bl*********
*“**All jets” (44%)*
***tt ************ bqq******′******bqq****′*
***“******Tau + X” (21%)***

- A. Ivanov,   UC Davis

- Feb-13-2006

## Detecting the Top

- Signal:
- Triggering on lepton
- High missing transverse energy (ET)
- High ET jets, central and spherical
- Two b-jets (displaced vertex)
- Background:
- W+jets:
-  dominant in leptonic modes
-  fakes the second lepton
- Drell-Yan(dileptons): no  ET
- QCD: huge in HAD mode

**e****+**

**e****-**

- ET

**jet 1**

**jet 2**

- A. Ivanov,   UC Davis

- Feb-13-2006

## Production 

**Cross Section Measurements**

- Testing non-standard model top production mechanisms
- Top sample might contain an admixture of exotic processes

- A. Ivanov,   UC Davis

- Feb-13-2006

## Cross Section in Dilepton channel

**L =750 pb****-1**

- New

******(tt)*****  *****= 8.3 ± 1.5 ****(stat)**** **
**± 1.0 ****(syst)**** ± 0.5 ****(lumi)**** pb***** ***

******(tt)*****  *****= 8.6 ± 2.3 ****(stat)**** **
**± 1.1 ****(syst)**** ± 0.6 ****(lumi)**** pb***** ***

|  | obs | expected |
| --- | --- | --- |
| ee | 12 | 14.3 ± 2.2 |
|  | 24 | 16.1 ± 2.4 |
| e | 28 | 25.0 ± 1.5 |

|  | obs | expected |
| --- | --- | --- |
| ee | 5 | 4.5 ± 0.5 |
|  | 2 | 3.8 ± 0.5 |
| e | 21 | 15.8 ± 2.8 |

- A. Ivanov,   UC Davis

- Feb-13-2006

## Lepton+jets cross section

- 230 pb-1

- Topological/kinematical analyses:
- Neural Network (CDF) / Likelihood Discriminant(D0)

- New

******(tt)*****  *****= 6.0 ± 0.6 ****(stat)**** ± 0.9 ****(syst)**** pb***** ***

******(tt)*****  *****= 6.7 ± 1.4 ****(stat)**** ± 1.4 ****(syst)**** pb***** ***

- A. Ivanov,   UC Davis

- Feb-13-2006

## Lepton + Jets with b-tagging

**Double b-tag**
**N****btags****≥2**

**N****btag****==1**

- B-jets are tagged by finding displaced vertex within a jet
- B-quark lifetime c ~ 450 m
- Reduces backgrounds, increases purity of ttbar

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Quark Pair Production: Summary

- A. Ivanov,   UC Davis

- Feb-13-2006

## Single Top Search

- s = 0.88 pb; t = 1.98 pb;  (~|Vtb|)
- Lepton + jets, ≥1 b-tag
- Overwhelming W+jets backgrounds
- Dedicated 2D Likelihood  fitter
- Best world’s upper limits so far
- Expect 3evidence with 2fb-1

- Harris et al PRD 66 054024(2002)

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Mass Measurements

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top mass relation to Higgs 

- Top quark mass is a fundamental parameter of SM
- Radiative corrections to SM predictions dominated by top mass
- Together with W mass places a constraint on Higgs mass

- A. Ivanov,   UC Davis

- Feb-13-2006

##  CDF Lepton+jets

- Constrain m(jj) = mW , m(lυ) = mW
-       and m(lυb) = m(jjb)
- 24 possibilities for 0 b-tags
- 12 possibilities for 1 b-tag
- 4 possibilities for 2 b-tags
- Select configuration with best 2 fit -> obtain Mreco

- 2005 New: Jet Energy Calibration in situ
- Simultaneous fit to invariant mass of W->jj
- Global factor used to correct energies of jet
- Reduces systematic uncertainty

- A. Ivanov,   UC Davis

- Feb-13-2006

## CDF Mtop Measurement in Lepton+Jets

- Up to date the best single measurement in the world!
- Better than Tevatron Run I average
- Will be shortly updated with ~750 pb-1

***PRD: hep-ex/0510048***
***PRL:  hep-ex/0510049***
***(accepted)***

- 

- A. Ivanov,   UC Davis

- Feb-13-2006

**Notes:**
Turn systematic uncertainty into a statistical one

## Future Projection

- Expect significant reduction in JES uncertainty with more data
- Turning JES systematic into a statistical uncertainty

| Systematic Source | Uncertainty
(GeV/c2) |
| --- | --- |
| Radiation | 0.7 |
| Model | 0.7 |
| b-jet | 0.6 |
| Method | 0.6 |
| PDF | 0.3 |
| Total | 1.3 |
| Jet Energy | 2.5 |

- A. Ivanov,   UC Davis

- Feb-13-2006

##  DO Matrix Element Technique

- Made best single measurement in Run I
- Form probability for each event:
- Consider all permutations
- Maximize Likelihood:  i Pi (x;Mtop)

***d******n************ : LO Matrix element***

-  ***f(q): parton density functions***

-  ***W(x,y): transfer function between jet and parton momenta***

- Use LO ME for ttbar and W+jets
- Run II Improvements: W->jj energy calibration
- No a priori energy determination

- A. Ivanov,   UC Davis

- Feb-13-2006

## CDF Dilepton Matrix Element Mtop Measurement (750 pb-1)

- DIL mode:
- Reduced combinatorics
- Only two possible parton-jet assignments
- Unconstrained kinematics: two neutrinos in the final state
- Background L0 Matrix Element treatment
- Best single measurement in Dilepton channel!

***m******top****** *****= 164.5 ± 4.5 ****(stat)**** ± 3.1 ****(syst)**** GeV***** /c ******2****** ***

- New

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Mass: Summary 

- 2nd plot with projection

- Expect to get down to 1.5 GeV total uncertainty on top mass

- A. Ivanov,   UC Davis

- Feb-13-2006

## Searches for ttbar  Resonances

- Various exotic models predict the existence of particles decaying to ttbar:   Topcolor-Assisted Technicolor
- (Hill, Phys Lett. B345, 483 (1995); Hill and Parke Phys. Rev. D49, 4454 (1994))
- Extends technicolor models and attempts to explain EWSB by introducing a new strong interaction
- Predicts new massive bosons “topgluons” and a topcolor Z’

- A. Ivanov,   UC Davis

- Feb-13-2006

**Notes:**
Various exotic models predict the existence of particles decaying to tt
    Topcolor-Assisted Technicolor
      (Hill, Phys Lett. B345, 483 (1995); Hill and Parke Phys. Rev. D49, 4454 (1994))

Extends technicolor models and attempts to explain EWSB by introducing a new strong interaction

Predicts new massive bosons “topgluons” and a topcolor Z’ 

## History: Previous Measurements

- Observed quite intriguing excess around 500 GeV
- Had a similar although smaller excess in Run 1

- CDF
- Run 1

- Lepton + jets:

- Phys.Rev.Lett. 85, 2062 (2000)

- A. Ivanov,   UC Davis

- Feb-13-2006

## D0 searches

- No similar anomaly seen in D0 data

- Lepton + jets:

- D0
- Run 1

- Phys.Rev.Lett. 92, 221804 (2004)

**Excluded with 95%CL**
**M****Z’**** < 680 GeV**
**(********Z’**** = 0.012M****Z’****)**

- A. Ivanov,   UC Davis

- Feb-13-2006

## Latest CDF measurement (682pb-1)

- Alas! With about twice more data the excess has washed out!

- New

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Quark

**Properties**

- I will cover only the latest measurements:
- Top Charge
- Top lifetime
- New heavy top in the top sample?

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Charge

**   **Is it the Standard Model top ?
-    W.-F. Chang et al.,Phys. Rev. D 59, 091503 (1999), (hep-ph/9810531) proposes an exotic doublet of quarks (Q1, Q4)R with charges (-1/3,-4/3) and M ~ 175 GeV
-   Right-handed b quark mixes with the isospin +1/2 component
-   while Mtop ~ 274 GeV  escaped detection
-    q = -4/3 is consistent with EW data, new b-couplings  improve the EW fit (E. Ma et al. , hep-ph/9909537)

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Quark Charge Measurement

- Lepton+jets, double b-tag events
- Determine:
-    charge of W (lepton)
-    pairing between W and b (2 fit)
-    flavor of b-jet

-  ***Jet Charge:   ***
***    ******Q******jet****** = ************q******i****** p******Ti******0.6******/ ************ p******Ti******0.6***
***(sum over tracks within a jet)****** ***

**365 pb****-1**
**17 events**
**34 tops**

-  ***Q******top,1****** = | q******l****** + q******,b(l)****** | Q******top,2****** = | - q******l****** + q******,b(j)****** | ***

- Perform likelihood ratio test

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Quark Charge Measurement

- Lepton+jets, double b-tag events
- Determine:
-    charge of W (lepton)
-    pairing between W and b (2 fit)
-    flavor of b-jet

-  ***Jet Charge:   ***
***    ******Q******jet****** = ************q******i****** p******Ti******0.6******/ ************ p******Ti******0.6***
***(sum over tracks within a jet)****** ***

**365 pb****-1**
**17 events**
**34 tops**

-  ***Q******top,1****** = | q******l****** + q******,b(l)****** | Q******top,2****** = | - q******l****** + q******,b(j)****** | ***

- Excluded Q=4/3 with 94%CL

- Perform likelihood ratio test:

- A. Ivanov,   UC Davis

- Feb-13-2006

## Top Lifetime

- Within the SM top ~10-24 s
- Long-lived top?
- Use **d****0**-lepton impact parameter with respect to beamline
- Determine detector resolution from
-     Z0/γ -> e+e-/μ+μ-

- c < 52.5 m with 95% CL

- Fit combination of signal/BG
- templates to the data: lepton+jets with >=1 b-tag

- A. Ivanov,   UC Davis

- Feb-13-2006

## New Heavy Particles Decaying to Wq?

- Can be a fourth generation up-type quark
-      He/Polonsky/Su (hep-ph/0102144)
-      a generic 4th chiral generation is consistent with EWK data; accommodates a heavy Higgs (500 GeV) without any other new physics
- “Beautiful Mirrors” model
-      Wagner et al  (hep-ph/ 0109097)
-     predicts  a new heavy up-type quark decaying to Wb; naturally accomodates the LEP b forward-backward asymmetry results
- From the precision EWK data the mass splitting between a t' and a b' quark is relatively small. Therefore if  Mt’ < Mb’ + MW:     t' -> W b(q)  (promptly)
- CDF Search in Lepton + jets channel: 2D-fit with
- HT = sum of transverse momenta of all objects in the event
- Mreco from 2-fit

- A. Ivanov,   UC Davis

- Feb-13-2006

## Search for t’->Wq 

- Excluded t'
- 196 <mt' < 207 GeV

- Set a limit on 4th generation up-type quark pair production
- Data did not cooperate well

- A. Ivanov,   UC Davis

- Feb-13-2006

## Conclusions

**  **Future is now! We are taking and analyzing Tevatron data
-  Many other analyses utilizing datasets of integrated luminosity ~700 pb-1 are being finalized
-  Results will be presented at the forthcoming Winter conferences
-  Stay tuned for 1fb-1 results at the Summer conferences (x10 of Run I)
-  No evidence for the top quark being non-Standard Model so far
-  More precise measurements of the top mass (~1.5 GeV uncertainty) and other quantities coming soon

- A. Ivanov,   UC Davis

- Feb-13-2006