1. Constraints on PDF uncertainties from CDF
DIS 2006, Tsukuba
Cigdem Issever
for the
CDF Collaboration
University of Oxford

2. 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
DIS
C. Issever

3. Tevatron proton-antiproton collisions s = 1.96 TeV (Run I  1.8 TeV)
Main Injector
(new)
Tevatron DØ
CDF
Chicago 
p source
Booster
Tevatron
proton-antiproton collisions
s = 1.96 TeV (Run I  1.8 TeV)
36 bunches: 396 ns crossing time
Peak luminosity is now ~ 1032 cm-2 s-1
Ultimately 4 – 9 fb-1 by 2009
DIS
C. Issever

4. CDF Recorded Data 1.6 fb-1 delivered EWK results 1.2 fb-1 recorded
Jet results with 1.0 fb-1
1.6 fb-1 delivered
1.2 fb-1 recorded
EWK results
DIS
C. Issever

5. CDF RUN II Detector Upgraded for RUN II New silicon tracking PLUG Muon
New drift chamber
Increased muon coveraged
New TOF
New plug calorimeters
Muon
COT Tracker
Si Detector
PLUG
EM Cal
Had Cal
CDF Data taking effi 80% - 85%.
Silicon Detector
DIS
C. Issever

6. 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
DIS
C. Issever

7. 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
ET>20GeV
PT>20GeV
Position of μ consistent with extrapolated track
ET>25GeV
PT>20GeV
W± signature: Isolated Energetic Lepton + ET
Z Signature: Two Isolated Energetic Leptons (opposite charge)
DIS
C. Issever

8. W cross section in the forward region
Extension into forward region:
1.2 < |η| < 2.8 using calorimeter seeded tracking
Complementary to central
DIS
C. Issever

9. W cross section in the forward region
Systematics on A = :
48165
~4.8% 2%
0.07
Axε
DIS
C. Issever

10. W cross section in the forward region
223pb-1
σ = /-0.013(stat) – (syst) +/ (lum.)nb.
NNLO 1.96 TeV, Stirling, van Neerven = (Th)
DIS
C. Issever

11. Central-to-Forward W vis. cross section ratio
s(visible)=sTOT*A where A is the kin. and geo accept.
Strategy: assign sys uncertainties but PDF, NLO/NNLO effect to svis
In this way:
Most of the luminosity uncertainty cancels in the ratio
All other uncertainties are uncorrelated
Accuracy can be used to constrain PDFs
DIS
C. Issever

12. Central-to-Forward W vis. cross section ratio
svis(central) =664.2±11.7 pb (Ete>25, ETn>25, |hele|<1)
svis(forward) =718±21 pb (Ete>20, ETn>25, 1.2<|hele|<2.8)
svis(central)/svis(forward) =0.925±0.033
1% assigned as luminosity syst. (slightly overestimate)
NLO ratios (taking into account correlations between central and forward):
CTEQ= ±0.037
MRST01E= ±0.011
Most uncertainties will go down with more data  useful to constrain PDFs
DIS
C. Issever

13. Z → μμ cross section (|η| < 1) using 337 pb-1
116 66
σ=261.2 ± 2.7 (stat) (sys) ± 15.1 (lum) pb
TeV Stirling, van Neerven σ(pp→Z)= (Th)
DIS
C. Issever

14. 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= (stat)+-21(syst)+-15(lumi) pb
DIS
C. Issever

15. Cross section summary
new
DIS
C. Issever

16. W Charge Asymmetry e+ W+ W- W+ n yW
proton
anti-proton W- W+ yW
proton
antiproton
Asymmetry in W production complicated by unknown n pz use lepton asymmetry:
which convolves W production with V-A decay.
DIS
C. Issever

17. W Charge Asymmetry Run II 170pb-1
A as function of ET provides better probe of x dependence.
Statistic allowed two bins.
Will be included into next generation of PDFs.
DIS
C. Issever

18. 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 yW
Determination of yW with W mass constrain gives 2 possible solutions.
Evaluate weight factor F1,2 for each y1,2 solution.
Parameterize F1,2 with
the angular distribution of (1+-cosΘ*)2
with W cross section, σ(yW), but this depends on asymmetry
Iterative procedure!!
DIS
C. Issever

19. W charge asymmetry – new method
Iterative procedure
Smaller statistical errors
Greater sensitivity
No additional systematics due to new method
DIS
C. Issever

20. Midpoint jet cross section
Good agreement with NLO
More details see talk of Olga Norniella in (HFS-5): Jets 1
DIS
C. Issever

21. Results with KT: Data/NLO; 1fb-1
IR and CL safe
No splitting or merging
Measurements in the forward region will allow to reduce the PDFs uncertainties
DIS
C. Issever

22. New generation of W&Z measurements (R, W Charge Asymmetry, … )
Conclusions
New cross section measurements from CDF
W → eν 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 → τe τh 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
dσ/dy for W → eν
dσ/dpt 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 !!
DIS
C. Issever

23. Backup Slides
DIS
C. Issever

24. 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
DIS
C. Issever

25. Z → μμ cross section (|η| < 1)
DIS
C. Issever

26. Z →τe τh cross section
taus difficult to reconstruct at hadron colliders
Z→ττ exploits event topology to suppress backgrounds (QCD&W+jet)
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)
π0 required in isolation cone (identified by shower maximum detector)
= 30o
Z→ττ event selection:
τ→e: electron + isolated track (ET>10 GeV)
τ→h: PT(seed) > 6 GeV & PT(signal)>15 GeV
remove backgrounds by event topology cuts
DIS
C. Issever

27. Z→ττ cross section
DIS
C. Issever

28. Z→ττ cross section -- Systematics
DIS
C. Issever

29. W Asymmetry – new method
Leading order W production
from Bo Young Han
DIS
C. Issever

30. ratio of two angular distributions at each rapidity
I. The angular distribution of ( )2 from W production
in Collin-Soper frame
The W production Probability from angular distribution
ratio of two angular distributions at each rapidity
from Bo Young Han
DIS
C. Issever

31. II. Weight must also depend on W+- cross-section.
But cross-sections depend on W asymmetry!
This method must be iterated.
III. Iteration procedure
Input
data
reconstruction
measuring
asymmetry
if no,
min( ) F1 Fn
the closest
asymmetry to data
assumed
sample
new assumed
sample No
Yes
from Bo Young Han
DIS
C. Issever

32. Sensitivity Study Selecting W events
, 400pb-1 MC data generated by Pythia
Selecting W events
high PT electron : ET > 25 GeV
Missing ET > 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
DIS
C. Issever

33. Systematic Uncertainty
Weight Factors depend on Q(yW, PtW) and σ(yW)
Ratio of two angular distributions, Q(yW, PtW)
PDF dependence
W cross section, σ(yW)
from Bo Young Han
DIS
C. Issever

34. Systematic Uncertainty (cont.)
The uncertainties from the energy measurement
Energy scale
Energy resolution (not yet)
Electron ET scale
±0.1%(1σ) : |η| < 1.1
±0.15%(1σ) : |η| > 1.1
Missing ET scale
W boson Recoil energy tuning
from Bo Young Han
DIS
C. Issever