# Presentation: 014199

## Petra Merkel

- Fermilab
- For the CDF Collaboration
- EPS 2003
- Aachen

## The New CDF Detector

- Fully digital DAQ (132ns)
- Pipelined trigger (drift chamber tracks @ L1, silicon tracks @ L2)

- Searches with Top - P.Merkel, Fermilab - CDF

## Top Physics

**p**

**p**

- -

**X**

**t**

**t**

- -

**b**

**b**

- -

**W****-**

**W****+**

**l****+****,q**

******,q’**

**-**

**l****-****,q**

******,q’**

**-**

**-**

**Production cross section **
**Production kinematics**
**Resonant production **
**Spin correlations**

**Top mass**
**Top Pt**

**Decay modes**
**Branching ratios**
**|V****tb****|**
**Rare/non-SM decays**

**W helicity**

- Exciting possibilities
- Third generation, high mass...
-  Special role in EW symmetry breaking?

**BSM?**
**(SUSY, **
**technicolor, **
**...)**

- Searches with Top - P.Merkel, Fermilab - CDF

**Notes:**
Analysis of production and decay kinematics
Resonant production
W helicity
Spin correlations
Single top production
Vtb
Rare and forbidden decays
Mt with 3 GeV/c2 precision

## Kinematics of Top Events

- Searches with Top - P.Merkel, Fermilab - CDF

## Pt(top)

- Phys.Rev.Lett. 87, 102001 (2001)

-  Measure Pt of hadronically decaying top in l+jets tt channel
-  Constrain Mtop=175 GeV, perform kinematic fit
-  In 106 pb-1: 61 evts found
-  BG estimate: 31.9+-4.6 evts
-  Use unsmearing procedure and unbinned likelihood fit to extract true Pt(top)

- Upper limit:
- R4(225<Pt<425GeV/c)<0.16 @ 95% C.L.

- CDF Run I

| True pT Bin | Parameter | Measurement | SM Expectation |
| --- | --- | --- | --- |
|  | R1 |  | 0.41 |
|  | R2 |  | 0.43 |
|  | R3 |  | 0.13 |
|  | R4 |  | 0.025 |
|  | R1+R2 |  | 0.84 |

- 0-75 GeV

- 225-300 GeV

- 150-225 GeV

- 75-150 GeV

- Searches with Top - P.Merkel, Fermilab - CDF

## Search for Higgs in W+2jets Events

- RunI W+jets

- Searches with Top - P.Merkel, Fermilab - CDF

## Heavy Flavor Content

-  We also looked for additional heavy flavor
-   “Superjets”: 2nd-vertex-tag AND soft-lepton-tag
-  statistics limited: 14 evts observed, 4.4±0.6 expected in W+2,3 jets bin (while good agreement when integrating over all Njet bins)
-  many checks performed in order to understand this slight excess
-  either statistical fluctuation OR mis-undertsanding of detector OR new physics...
-  Need more data from RunII to re-evaluate this analysis

- RunI superjets

-  0.4% probability of consistency w/ SM in the 4 jet bins
-  “a posteriori” probability of consistency in 2jet bin  is P=10-3

- Phys.Rev.D65, 052007 (2002)

- Searches with Top - P.Merkel, Fermilab - CDF

## Search for tt Resonances

- X boson with mX < 560 GeV/c2

- -

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

- Expected sensitivity for RunII:
- (*B)~90 fb

- Searches with Top - P.Merkel, Fermilab - CDF

**Notes:**
Use Bayesian statistics to derive posterior probability distns by fitting mttbar from data weighted to sum of 3 sources.
Write Nx=A*L*Sx*B, can define Sx*B at 95% CL.
No statistically significant excess is found.

Large value of Mtop suggests the introduction of new strong dynamics into SM

Leptophobic Z’ results in large sigma(tt)

## Search for V+A

- F0 = 70% longitudinal
- F- = 30% left-handed
- [V+A: 70% long., 30% r.-h.]

- Use invariant mass of lepton and b quark (frame independent):**                       ****M****2****l****b**** = 1⁄2 (M****2****t**** – M****2****W****)(1 + cosΨ*********l****)**

- Fit for fraction of right-handed (V+A) component: fV+A

- RunI

- Phys.Rev.Lett. 84, 216 (2000)

- Verify that this is the top quark of the SM...

- Searches with Top - P.Merkel, Fermilab - CDF

**Notes:**
Analysis makes use of the asymmetry in the lepton’s decay angle b/w left-handed and r-handed W’s from top decay.
For left-handed W’s, the lepton tends to be produced in the direction of the b due to the spin being opposite its momentum.
For right-handed W’s, the lepton is opposite the b because the spin is in the direction of its momentum.
This results in an asymmetry in the Mass distribution between V-A theory (70% longitudinal, 30% left-handed)
And V+A theory (70% longitudinal, 30% right handed).  This can be used to discriminate b/w them.

## V+A Results

- Using M2l+b

- CDF I  preliminary

- CDFI Result (109pb-1):
- (Using tt dilepton, and lepton+jets
- events with 1 and 2 SVX b-tagged jets)
** ****f****V+A****= -0.21**** ****+0.42****-0.25**** ± 0.21**

- -

- Using Pt(l)

- Expected sensitivity for RunII:
- tW0tW+

- Searches with Top - P.Merkel, Fermilab - CDF

**Notes:**
The result is the combined result of all three samples, and comes from a binned likelihood fit based on poisson fluctuating background, V-A, and V+A templates to get the best agreement with the data.  
The dominant source of systematic uncertainty is due to the uncertainties in the top mass.  Although correlations with
The jet energy scale uncertainty make this effect smaller and tend to cancel out the JES systematic somewhat.
The plot is just for the SVX single tagged sample (not the other two samples or the combined).  There are 15 events in that sample, or 15 Mlb’s.  The combined measurement uses 53 Mlb’s from all 3 samples.

## Search for H+:

-  Predict excess of top events with tau leptons!
-  Direct search for signature of  lepton in t decays  upper limit on B(tH+b)
-  Signature:
-  In 106pb-1     4 candidates found
-  Expect: 4.0+-0.6 from SM (BG+top)

- Very
- interesting
- channel
- for RunII

- Phys.Rev.D62, 012004 (2000)

- CDF RunI

- Expected sensitivity for RunII:
- tWbtXb

- Searches with Top - P.Merkel, Fermilab - CDF

## Search for FCNC Decays

- Rare decays: tq, tqZ
- Look for tt events w/ tq and the other tWb(lb or qqb)
- <1 evt expected from SM BG sources
- 1 evt found in 110pb-1: Pt()=72GeV, Et()=88GeV, Et=24GeV, 3 jets
- Also kinematically consistent w/ tW+b & tW-b, but Et() exceptionally large!
- B(tc+) + B(tu+) < 3.2% @ 95% C.L.
- Look for tt events w/ tqZ(qee or q) and the other tWb(qqb)
- Less sensitive because B(Zleptons) small
- 1.2 evts expected from SM BG sources
- 1 evt found in 110pb-1: Z + 4 jets
- Kinematics fit better the Z+multijet hypothesis than FCNC decay
-  B(tc+Z) + B(tu+Z) < 33% @ 95% C.L.

- /

- -

- -

- CDF RunI

- Phys.Rev.Lett. 80, 2525 (1998)

- -

- -

- Unusual decays of the top quark might provide insight into the mechanism of EW symmetry breaking

- Searches with Top - P.Merkel, Fermilab - CDF

## Tevatron Performance

-  Stable data-taking since June ‘02 shutdown ~ 200 pb-1 on tape
-  ~ 5-8 pb-1/wk @ > 90% efficiency
-  Record instantaneous luminosity after January shutdown ~4.7-1031cm-2s-1

- Most of the RunII results so far used 72 pb-1 (March ‘02 – January ‘03)
- New results from ~120 pb-1 expected soon!

- -

- Searches with Top - P.Merkel, Fermilab - CDF

## Top in RunII 

- First cross section and Mtop measurements using 72pb-1
- New results from ~125pb-1 expected soon

- Some searches are already on the way, like single top and V+A

- Expected sensitivity for RunII:
- tt

- Expected sensitivity for RunII:
- tGeV

- Searches with Top - P.Merkel, Fermilab - CDF

## Summary & Outlook

| Measurement | Estim.uncertainty | Tests |
| --- | --- | --- |
| Mt | 2-3 GeV/c2 | Indirect MH |
| tt | 7% | QCD couplings |
| ll/l+j | 12% | Non-SM decays |
| B(tWb)/B(tWX) | 2.8% | “ |
| B(tWb)/B(tXb) | 9% | “ |
| B(tWlong) | 5.5% | Non-SM couplings |
| B(tWV+A) | 2.7% | “ |
| *B(Z’tt) | ~90 fb | exotics |

- Searches with Top - P.Merkel, Fermilab - CDF

## BACKUP SLIDES:

- Searches with Top - P.Merkel, Fermilab - CDF

## Mtop   versus   # of jets

- Searches with Top - P.Merkel, Fermilab - CDF

**Notes:**
It has been suggested there is a hint of increase of the top mass with number of jets; values agree within errors

## Pt(ttbar)

- Searches with Top - P.Merkel, Fermilab - CDF

## EWSB

**M****w**** ****: CDF ******** D******
** ********M**** ~ 30 MeV (2 fb****-1****)**
** ********M**** ~ 20 MeV (10 fb****-1****)**
**M****t**** ****: CDF or D******** **
** ********M**** ********  4 GeV (2 fb****-1****) **
** ********M**** ********  2 GeV (10 fb****-1****)**

- Searches with Top - P.Merkel, Fermilab - CDF

## Anomalies in the Top Quark Sample?

-  found in dilepton sample
-  electron in crack called jet
- 180 GeV ET electron!
- 110 GeV missing ET !

- CDF Run 1 Trilepton Event

- Searches with Top - P.Merkel, Fermilab - CDF

## Search for Single top

- CDF I has performed searches for s and t channels separately in RunI
- CDF I  has also searched for combined process:

-  If SM is correct, observation in RunIIa
-  Expect about 100-150 events in 2 fb-1
-  Measure |Vtb| with 10-15% precision** **

-  Search for anomalous couplings - large production rates or anomalous angular distributions
-  Background to Higgs

-  (t) < 14 pb at 95% C.L.

- Phys.Rev.D65, 091102 (2002)

- Searches with Top - P.Merkel, Fermilab - CDF

**Notes:**
Single top processes are harder to observe than tt production:  final states containing fewer jets suffer from higher
background, and a priori no sensitivity expected in Run 1 data unless new physics processes enhance production rate.

## Kinematics in Dilepton Events

- hep-ph/9609313

- Searches with Top - P.Merkel, Fermilab - CDF