# Presentation: 414582

##  Top Mass Measurement at CDF

** ****Top Mass Measurement at CDF**

- Kostas KORDAS
- INFN – Frascati

-   Frontier Science 2005
-  Milano, 12-17 Sept. 2005

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Top mass unpredicted in Standard Model (SM), but related to W, Higgs 	 (and other observables).

   (Higgs is mass giver to all)

When all W, t, H measured:
                test SM 
   (and to test you have to measure well...)

Radiative corrections affect observables

   Game of ElectroWeak fits

**Top mass** unpredicted in Standard Model (SM), but **related to *****W, Higgs*** 	 (and other observables).
-    (Higgs is mass giver to all)
- When all *W, t, H* measured:
-                 test SM
-    (and to test you have to measure well...)
- Radiative corrections affect observables
-    Game of ElectroWeak fits

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

**Notes:**
26 Apr 2005

## Top first observed at  CDF & D0 in 1995.  Tevatron’s Run I: ~110pb-1 per exp.

Run I Average:

- Top first observed at  CDF & D0 in 1995.  Tevatron’s Run I: ~110pb-1 per exp.
- Run I Average:

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Where do we get top quarks?

- 1fb-1 per experiment on tape
- ~1.3 fb-1 delivered luminosity
- Peak luminosity 1.4 x 1032cm-2s-1
- Presented here: 320 – 360 pb-1

- Goal of Run II per experiment:

- (1 fb-1 ~ 6 x 1013 collisions, ~ 6.5 x 103  top pairs)

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Top production and decay

-  _Production_: mainly

-  _Decay_: BR(t  W b) ~ 100%

-  All-hadronic:    44%
-  **Lepton + jets: 30%**
-  Dilepton:            5%

- W decay defines
-       decay mode

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop measurement challenge (I)

**Measure: **e, , jets, tracks,
- Association to top daughters?
- Background events?
**Dileptons**: extra lepton, only
-     2 jets (but 2 ’s 1     , low stat)
-  **B-tagging helps a lot!**

- Best case!

- Lepton + jets event:

| B-tags | Jet assignments |
| --- | --- |
| None | 24 |
| 1 | 6 |
| 2 | 2 |

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Scale from “1st principles”:  ~3%
What about standard candles?
    W  jet jet  (use W in top events)

- What about standard candles?
-     *W **** jet jet*  (use *W* in top events)

- Mtop** measurement challenge (II)**

** **_**Accuracy of measurements**_
**  **Dominant uncertainty:
-       Jet Energy Scale (JES)
-    jetquark energy mapping

- Run I  world average uncertainty (±4.3 GeV/c2):
-     2.6 GeV/c2 from JES
-     2.7 GeV/c2 from stat.

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop lepton+jets (1D template method)

- Templates

- 2 mass fitter:Impose mass constraints, find best top mass &
- jet-parton assignment  One Mtop per event
- Additional selection cut on resulting 2

- Result

- Likelihood fit:Best signal + bkg templates to fit dataCompare to parameterization, not directlyConstraint on background normalization

- Likelihoodfit

- Massfitter

- Mtop** *****lepton+jets***** ****(1D *****template method)***

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop lelpton+jets: 1D templates

- Mtop** *****lelpton+jets*****: 1D templates**

| Sample | Jet ET cut [ GeV ] | S/B | <bkg> | Events |
| --- | --- | --- | --- | --- |
| 2 b-tags | 3 jets ET > 15, 4th jet ET >15  | 18:1 |  | 16 |
| 1 b-tag | (T) 4 jets  ET > 15  | 4:1 |  | 57 |
| 1 b-tag | (L) 3 jets ET > 15, 4th jet 8 < ET <15 | 1:1 |  | 25 |
| 0 b-tags | 4 jets ET > 21  | N/A | N/A | 40 |

-  Exclusive
-   samples
-   in # b-tags

**Signal Template**

**Background Template**

- # background
- constrained
- to prediction
- (except for
-   0-tag)

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop using Wjet jet: 2D templates

**e**
****

**jet**
**jet**

**m****jj****(W)**

-  Sensitive to Jet Energy Scale (JES)
-  minimal sensitivity to Mtop

- Constrain to a-priori JES estimate

**Find best (M****top****, JES)**
**to fit data**

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop lepton+jets (2D): result

** ****2D template method (using W******** jet jet):**

- Mtop** *****lepton+jets *****(2D): result**

- best single measurement
- better than Run I average

- 1D template:

- (318 pb-1)

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop lepton+jets systematics (2D)

| Systematic
Source | 2-D fit
Mtop (GeV) | 1-D fit
Mtop (GeV) |
| --- | --- | --- |
| JES | 2.5  | 3.1 |
| b-jet modeling | 0.6 | 0.6 |
| ISR | 0.4 | 0.4 |
| FSR | 0.6 | 0.4 |
| PDFs | 0.3 | 0.4 |
| Generators | 0.2 | 0.3 |
| Bkg shape | 1.1 | 1.0 |
| b-tagging | 0.1 | 0.2 |
| MC statistics | 0.3 | 0.4 |
| Method | 0.5 | - |
| TOTAL | 3.0 =
2.51.7 | 3.4 =
3.11.5 |

-  Jet Energy Scale dominates
-  In-situ calibration improves w/ statistics

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop lepton+jets: Dynamical Likelihood

- 4 jets ET > 15 GeV , min.1 b-tagged
-  63 events,             expected bkg

- Mtop** *****lepton+jets*****: ****Dynamical Likelihood**

-  Implement knowledge transparently

**K. Kondo J. Phys. Soc. 57 4126 (1988)**

** ****Sample ****L ****= ********i**** L****i**** (x;M****top****)**
-  No background probability term
-  Map effect on reconstructed Mtop

- 14.5% bkg

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop lepton+jets: Dynamical Likelihood

- Mtop** *****lepton+jets*****: ****Dynamical Likelihood**

- Use mapping fcn
- for 14.5% bkg

- Mtop at max. L
- from each event

**Same uncert. as 2D template method**

- (318 pb-1)

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop dileptons: Neutrino Weighting

- Mtop** *****dileptons*****: Neutrino Weighting**

-  Assume: Mtop , MW ****of ****’s  Prob. to match measured
-  Integrate jet-parton assignments &  of ’s  **Prob vs. ****M****top**
-  Get most Prob. Mtop  rest is 1D** template method**

**B) Boost statistics:**
-     e or  + isolated track
-                 catch more ’s

- 45 evts

- 2.6 from JES uncertainty

- (359 pb-1)

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop dileptons: Matrix element

- Mtop** *****dileptons*****: Matrix element**

- A) Like Dynamical Likelihood,
-      w/ explicit bkg likelihood terms

- B) 2 identified e or 

- 33 evts

- (2.6 from JES)

**Most powerful dilepton method a-priori**
**& in practice**

- 340 pb-1

- 	    _*Weight   Pull*_
- Matrix El.     36%   -0.60
-  Weight      27%    0.42
- Kinematic      13%    0.33
-  Phi	      10%     0.20
- Run1 	      14%    -0.07

- (340 pb-1)

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop : combined results

** **Use exclusive datasets
-   (Runs, experiments, channels)
-  Combine best measurement
-   from each channel

-  NEW!   Combining dilepton Mtop at CDF

**Precision = 1.7% **

-  Dileptons are relevant:
-    - Important (8%) weight to Mtop
-    - Different physics “contamination”
-      of top samples

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## 1fb-1 per experiment on tape & Tevatron performing well!

New techniques applied for Mtop   also, never underestimate “simplicity” (e.g., templates with in situ W’s to calibrate jet energies)

Precision limited by systematics
Mtop measurement averages in progress:

- 1fb-1 per experiment on tape & Tevatron performing well!
- New techniques applied for Mtop   also, never underestimate “simplicity” (e.g., templates with in situ W’s to calibrate jet energies)
- Precision limited by systematics
- Mtop measurement averages in progress:

**Summary**

- As I said, to test
- you better measure
- well!     Need also

**18**

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## THE END
(for now...)

- (for now...)

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop : results

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

## Mtop lepton+jets (2D): samples

- Plain event count

- Weighted with likelihood

**All samples useful,**
**especially for  **
**JES calibration!**

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano

##  2) Matrix element techinques:

- Prob(event x | Mtop) = Prob(partons | Mtop)  x  Prob (event x | partons)* *

** ****1) lepton+jets 1D Template: the likelihood**

- Top Mass Measurement at CDF   -  Kostas KORDAS

- Frontier Science 12-17 Sept. 2005, Milano