constraints on pdf uncertainties from cdf dis 2006, tsukuba 22.04.2006 cigdem issever for the
DESCRIPTION
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) - PowerPoint PPT PresentationTRANSCRIPT
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Constraints on PDF uncertainties from CDF
DIS 2006, Tsukuba
22.04.2006
Cigdem Issever
for the
CDF Collaboration
University of Oxford
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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
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Main Injector(new)
Tevatron
DØCDF
Chicago
p source
Booster
Tevatronproton-antiproton collisionss = 1.96 TeV (Run I 1.8 TeV) 36 bunches: 396 ns crossing timePeak luminosity is now ~ 1032 cm-2 s-1
Ultimately 4 – 9 fb-1 by 2009
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CDF Recorded Data
Jet results with 1.0 fb-1
1.6 fb-1 delivered1.2 fb-1 recorded
EWK results
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CDF RUN II Detector
Si Detector
COT Tracker
EM Cal Had Cal
MuonUpgraded for RUN II• New silicon tracking• New drift chamber• Increased muon coveraged• New TOF• New plug calorimeters
PLUG
Silicon DetectorCDF Data taking effi 80% - 85%.
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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
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ET>25GeV
W/Z Gauge Bosons Identification
• At hadronic collider W and Z bosons hadronic decays are overwhelmed by QCD background.
identification through leptonic decays
We Z
W± signature: Isolated Isolated Energetic Lepton + EEnergetic Lepton + ETT
Z Signature: Two Isolated Energetic Two Isolated Energetic Leptons (opposite charge)Leptons (opposite charge)
PT>20GeV
PT>20GeV
ET>20GeV Position of μ consistent with extrapolated track
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W cross section in the forward region
Extension into forward region:1.2 < |η| < 2.8 using calorimeter seeded tracking
Complementary to central
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W cross section in the forward region
48165 ~4.8%
LA
NN bkgobs
0.07
Systematics on A = 0.2567:
Axε
2%
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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)
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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
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• 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
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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)
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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
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Cross section summary
new
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W Charge Asymmetry
W- W+
yWprotonantiproton
u
d
dyWddyWd
dyWddyWdA
WW
WW
/)(/)(
/)(/)(
W+u de+
proton anti-proton
Asymmetry in W production complicated by unknown pz use lepton asymmetry:
which convolves W production with V-A decay.
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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.
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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
1. the angular distribution of (1+-cosΘ*)2
2. with W cross section, σ(yW), but this depends on asymmetry• Iterative procedure!!
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W charge asymmetry – new method
Iterative procedure
• Smaller statistical errors• Greater sensitivity• No additional systematics due to new method
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Jet
Midpoint jet cross section
Good agreement with NLO
More details see talk of Olga Norniella in (HFS-5): Jets 1
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Results with KT: Data/NLO; 1fbResults with KT: Data/NLO; 1fb-1-1
Measurements in the forward region will allow to reduce the PDFs uncertainties
IR and CL safeNo splitting or merging
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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 !!
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Backup Slides
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W forward cross section
Electron: Et > 20GeV1.2 < |η|<2.8
Neutrino: MEt > 25 GeV
Vertex: |z0| < 60 cm
Electron ID: Had/Em<0.05Isolation<0.1
Δ(XPES,XTrk) < 3 cm
Δ(YPES,YTrk) < 3 cm
E/P < 2.0
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Z → μμ cross section (|η| < 1)
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Z →τe τh cross section
CDF strategy for hadronic tau reconstruction:
1. Charge tracks define signal and isolation cone (shrinking cone vs. E)
isolation: require no tracks in isolation cone
2. Hadronic calorimeter cluster (to suppress e background)
3. π0 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 (ET>10 GeV)• τ→h: PT(seed) > 6 GeV & PT(signal)>15 GeV• remove backgrounds by event topology cuts
= 30o
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Z→ττ cross section
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Z→ττ cross section -- Systematics
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W Asymmetry – new method
Leading order W production
from Bo Young Han
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I. The angular distribution of ( )2 from W production
ratio of two angular distributions at each rapidity
*1 cos
* * 2 * 2(cos , , ) (1 cos ) ( , )(1 cos )W WW t W tP y p Q y p
– in Collin-Soper frame
– The W production Probability from angular distribution
*cos
q P q P q P q P
q P q P q P q P
q P q P q P q P
from Bo Young Han
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II. Weight must also depend on W+- cross-section.
– But cross-sections depend on W asymmetry! This method must be iterated.
III. Iteration procedure
*1,2 1,2 1,2
1,2 * *1 1 1 2 2 2
(cos , , ) ( )
(cos , , ) ( ) (cos , , ) ( )
Wt
W Wt t
P y p yF
P y p y P y p y
measuringasymmetry
the closest asymmetry to data
assumedsample
F1 min( )2new assumed
sampleFn
reconstructionInputdata
YesNo
if no,
from Bo Young Han
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Sensitivity Study , 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
W e
from Bo Young Han
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Systematic Uncertainty
Weight Factors depend on Q(yW, Pt
W) and σ(yW)
1. Ratio of two angular distributions, Q(yW, Pt
W)– PDF dependence
2. W cross section, σ(yW)– PDF dependence
from Bo Young Han
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Systematic Uncertainty (cont.)The uncertainties from the
energy measurement– Energy scale – Energy resolution (not
yet)
3. Electron ET scale– ±0.1%(1σ) : |η| < 1.1– ±0.15%(1σ) : |η| > 1.1
4. Missing ET scale– W boson Recoil energy
tuning
from Bo Young Han