# Presentation: 690910

## 
Constraints on PDF uncertainties from CDF

DIS 2006, Tsukuba
22.04.2006

Cigdem Issever
for the 
CDF Collaboration

University of Oxford

**Constraints on PDF uncertainties from CDF**
**DIS 2006, Tsukuba**
**22.04.2006**
**Cigdem Issever**
- for the
- CDF Collaboration
- University of Oxford

## Outline

**Introduction**
**Tevatron & CDF detector**
**EWK Results (95% of the talk)**
**Jet results ****(see talk “Inclusive jet production at the Tevatron (CDF)” of Olga Norniella in (HFS-5)**)
**Conclusion**

- C. Issever

- DIS 2006 22.04.06

##          Tevatron

**         ****Tevatron**

**proton-antiproton collisions**
******s = 1.96 TeV  (Run I ******** 1.8 TeV) **
**36 bunches: 396 ns crossing time**
**Peak luminosity is now ~ 10****32**** cm****-2**** s****-1**
**Ultimately 4 – 9 fb****-1 ****by 2009**

- C. Issever

- DIS 2006 22.04.06

## CDF Recorded Data

**Jet results with 1.0 fb****-1**

- 1.6 fb-1 delivered
- 1.2 fb-1 recorded

- EWK results

- C. Issever

- DIS 2006 22.04.06

## CDF RUN II Detector

**Si Detector**

**COT Tracker**

**EM Cal**

**Had Cal**

**Muon**

- Upgraded for RUN II
-  **New silicon tracking**
** ****New drift chamber**
** ****Increased muon coveraged**
** ****New TOF**
** ****New plug calorimeters**

- PLUG

**Silicon Detector**

**CDF Data taking effi 80% - 85%.**

- C. Issever

- DIS 2006 22.04.06

## EWK Physics – Input to PDFs

**EWK Physics – Input to PDFs**

**Motivation**
- Test SM (precise measurements)
**Constraints on PDFs**
- Search for physics beyond SM
**Important input to LHC**
**Outlook**
- W forward cross section, 223/pb
- Z →ττ and μμ cross Section, 330/pb
- W charge asymmetry, 170/pb

- C. Issever

- DIS 2006 22.04.06

## W/Z Gauge Bosons Identification 

**W/Z Gauge Bosons Identification**** **

**At hadronic collider W and Z bosons hadronic**** decays**** are overwhelmed by QCD background.**
****** ****identification through leptonic decays**

- We

- Z

**W****±**** ****signature**:  **Isolated Energetic  Lepton + E****T**

**Z Signature**: **Two Isolated Energetic  Leptons (opposite charge)**

**P****T****>20GeV**

**P****T****>20GeV**

**E****T****>20GeV**

**Position of ****μ**** consistent with extrapolated track **

- C. Issever

- DIS 2006 22.04.06

## W cross section in the forward region

**W cross section in the forward region**

**Extension into forward region:**
**1.2 < |****η****| < 2.8**** using calorimeter seeded tracking**

**Complementary to central**

- C. Issever

- DIS 2006 22.04.06

## W cross section in the forward region

**W cross section in the forward region**

- 48165

- ~4.8%

- 0.07

- _Systematics on A = 0.2567:_

- Axε

- 2%

- C. Issever

- DIS 2006 22.04.06

## W cross section in the forward region

- 223pb-1

- σ = **2.796 +/-0.013(stat) + 0.095 – 0.090 (syst) +/- 0.168 (lum.)nb**.

**NNLO ****σ****(pp→W) @ 1.96 TeV, ****Stirling, van Neerven**** = 2.687 +- 0.054(Th)**

- C. Issever

- DIS 2006 22.04.06

## Central-to-Forward W vis. cross section ratio

- (visible)=TOT*A where A is the kin. and geo accept.
- Strategy: assign sys uncertainties but PDF, NLO/NNLO effect to vis
- In this way:
- Most of the luminosity uncertainty cancels in the ratio
- All other uncertainties are uncorrelated
- Accuracy can be used to constrain PDFs

- C. Issever

- DIS 2006 22.04.06

##  vis(central) =664.2±11.7 pb (Ete>25, ETn>25, |ele|<1)
 vis(forward) =718±21 pb (Ete>20, ET>25, 1.2<|ele|<2.8)

 vis(central)/vis(forward) =0.925±0.033
1% assigned as luminosity syst. (slightly overestimate)

NLO ratios (taking into account correlations between central and forward):
 CTEQ= 0.9243±0.037
 MRST01E= 0.94137±0.011
Most uncertainties will go down with more data  useful to constrain PDFs

-  vis(central) =664.2±11.7 pb (Ete>25, ETn>25, |ele|<1)
-  vis(forward) =718±21 pb (Ete>20, ET>25, 1.2<|ele|<2.8)
-  ******vis****(central)/********vis****(forward) =0.925±0.033**
**1% assigned as luminosity syst. (slightly overestimate)**
- NLO ratios (taking into account correlations between central and forward):
** ****CTEQ= 0.9243±0.037**
** ****MRST01E= 0.94137±0.011**
**Most uncertainties will go down with more data ******** useful to constrain PDFs**

**Central-to-Forward W vis. cross section ratio**

- C. Issever

- DIS 2006 22.04.06

## Z → μμ cross section (|η| < 1) using 337 pb-1

- σ=261.2 ± 2.7 (stat) + 5.8 - 6.9 (sys) ± 15.1 (lum) pb

- 66

- 116

- 337pb-1

**NNLO @ 1.96 TeV Stirling, van Neerven ****σ****(pp→Z)=251.3+-0.5(Th)**

- C. Issever

- DIS 2006 22.04.06

## Z →τe τh cross section using 349 pb-1

-  316 signal events
-  60 % τ identification efficiency and 5% acceptance
-  Most systematics are data driven will be reduced with more stat.

- σ=265+-20(stat)+-21(syst)+-15(lumi) pb

- C. Issever

- DIS 2006 22.04.06

## Cross section summary

- new

- C. Issever

- DIS 2006 22.04.06

## W Charge Asymmetry

- Asymmetry in W production complicated by **unknown ******** p****z** use lepton asymmetry:

- which convolves W production with V-A decay.

- C. Issever

- DIS 2006 22.04.06

## W Charge Asymmetry Run II 170pb-1

**A ****as function of E****T**** provides better probe of x dependence.**
**Statistic allowed two bins.**
**Will be included into next generation of PDFs.**

- C. Issever

- DIS 2006 22.04.06

## W Charge Asymmetry – new method

**Lepton asymmetry has turn over at high |****η****| due to V-A**
**W charge asymmetry does not have this effect, so we don’t purely probe high**** y****W**

** ****Determination of y****W**** with W mass constrain gives 2 possible solutions.**
** ****Evaluate weight factor F****1,2**** for each y****1,2**** solution.**
** ****Parameterize F****1,2**** with**
**the angular distribution of (1+-cos****Θ*********)****2**
**with W cross section, ****σ****(y****W****), but this depends on asymmetry**
** ****Iterative procedure!!**

- C. Issever

- DIS 2006 22.04.06

## W charge asymmetry – new method

- Iterative procedure

-  **Smaller statistical errors**
** ****Greater sensitivity**
** ****No additional systematics due to new method**

- C. Issever

- DIS 2006 22.04.06

## Midpoint jet cross section

**Midpoint jet cross section**

- Good agreement with NLO

**More details see talk ** **of Olga Norniella in (HFS-5): Jets 1**

- C. Issever

- DIS 2006 22.04.06

## Results with KT: Data/NLO; 1fb-1

**Measurements in the forward region will allow to reduce the PDFs uncertainties**

- IR and CL safe
- No splitting or merging

- C. Issever

- DIS 2006 22.04.06

## Conclusions

**New cross section measurements from CDF**
**W → e****ν**** in forward region (1.2 < |****η****| < 2.8) using 223 pb****-1**
**Central-to-forward W vis cross section ratio**
**Z → ****μμ**** using 337 pb****-1**
**Z → ****τ****e**** ****τ****h**** using 349pb****-1**
**Inclusive Jets with Mitpoint using 1.04 fb****-1**
**Inclusive Jet s with Kt algorithm using 0.96 fb-1**
**Excellent base for next set of analyses**
**d****σ****/dy for W → e****ν**** **
**d****σ****/dp****t**** for Z → ****μμ**** **
**Tau widely used in SM measurements and SUSY, Higgs**
**New generation of W&Z measurements**
**(R, W Charge Asymmetry, ... ) **
**on the way !!**

- C. Issever

- DIS 2006 22.04.06

## Backup Slides

- C. Issever

- DIS 2006 22.04.06

## W forward cross section

| Electron: | Et > 20GeV
1.2 < |η|<2.8 |
| --- | --- |
| Neutrino: | MEt > 25 GeV |
| Vertex: | |z0| < 60 cm |
| Electron ID: | Had/Em<0.05
Isolation<0.1 |
|  |  Δ(XPES,XTrk) < 3 cm
 Δ(YPES,YTrk) < 3 cm
 E/P < 2.0 |

- C. Issever

- DIS 2006 22.04.06

## Z → μμ cross section (|η| < 1)

- C. Issever

- DIS 2006 22.04.06

## Z →τe τh cross section 

**CDF strategy for ****hadronic tau reconstruction****:**
**Charge tracks ******** define signal and isolation cone (shrinking cone vs. E)**
**isolation: require no tracks in isolation cone**
**Hadronic calorimeter cluster (to suppress e background)**
**π****0**** required in isolation cone (identified by shower maximum detector)**

** ****taus difficult to reconstruct at hadron colliders**
** ****Z→****ττ**** exploits event topology to suppress backgrounds (QCD&W+jet)**

**Z****→****ττ**** event selection:**
** ****τ→****e: electron + isolated track (E****T****>10 GeV)**
** ****τ→****h: P****T****(seed) > 6 GeV & P****T****(signal)>15 GeV**
** ****remove backgrounds by event topology cuts**

- = 30o

- C. Issever

- DIS 2006 22.04.06

## Z→ττ cross section

- C. Issever

- DIS 2006 22.04.06

## Z→ττ cross section -- Systematics

- C. Issever

- DIS 2006 22.04.06

## W Asymmetry – new method

**Leading order *****W*****  production**

- from Bo Young Han

- C. Issever

- DIS 2006 22.04.06

## I. The angular distribution of (            )2 from  W production

**ratio of two angular distributions at each rapidity**

**                  ****in Collin-Soper frame**
**  ****The W production Probability from angular distribution**** **

- from Bo Young Han

- C. Issever

- DIS 2006 22.04.06

## II. Weight must also depend on W+- cross-section.

But cross-sections depend on W asymmetry!
This method must be iterated. 

III. Iteration procedure

***But cross-sections depend on W asymmetry!***
***This method must be iterated.****** ***
**III****. ****Iteration procedure**

- measuring
- asymmetry

- the closest
- asymmetry to data

- assumed
- sample

- F1

- min(    )

- new assumed
- sample

- Fn

- reconstruction

- Input
- data

- Yes

- No

- if no,

- from Bo Young Han

- C. Issever

- DIS 2006 22.04.06

## Sensitivity Study

-            **, 400pb****-1**** MC data generated by Pythia**
**Selecting *****W***** events**
**high P****T**** electron : E****T ****> 25 GeV**
**Missing E****T ****> 25 GeV**
**Used CTEQ6M errors PDF 40 sets for PDF uncertainty**
**Comparison of statistical uncertainty between lepton and W boson asymmetry**
**Our method has statistical sensitivity to probe PDFs**

- from Bo Young Han

- C. Issever

- DIS 2006 22.04.06

## Systematic Uncertainty

**Weight Factors depend on ****Q(y****W****, P****t****W****)**** and ****σ****(y****W****)**
**Ratio of two angular distributions, Q(y****W****, P****t****W****)**
**PDF dependence**
**W cross section, ****σ****(y****W****)**
**PDF dependence**

- from Bo Young Han

- C. Issever

- DIS 2006 22.04.06

## Systematic Uncertainty (cont.)

**The uncertainties from the energy measurement**
**Energy scale **
**Energy resolution (not yet)**
** **
**Electron E****T**** scale**
**±0.1%(1****σ****) :  |****η****| < 1.1**
**±0.15%(1****σ****) : |****η****| > 1.1**
**Missing E****T**** scale**
**W boson Recoil energy tuning**

- from Bo Young Han

- C. Issever

- DIS 2006 22.04.06