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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. Outline. Introduction Tevatron & CDF detector EWK Results (95% of the talk)
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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
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
Chicago Booster CDF DØ Tevatron p source Main Injector (new) 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 C. Issever
CDF Recorded Data Jet results with 1.0 fb-1 1.6 fb-1 delivered 1.2 fb-1 recorded EWK results C. Issever
CDF RUN II Detector • Upgraded for RUN II • New silicon tracking • 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 C. Issever
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
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 ET>20GeV PT>20GeV Position of μ consistent with extrapolated track PT>20GeV W±signature: Isolated Energetic Lepton + ET Z Signature: Two Isolated Energetic Leptons (opposite charge) C. Issever
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
W cross section in the forward region Systematics on A = 0.2567: 48165 ~4.8% 2% 0.07 Axε C. Issever
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
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 C. Issever
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= 0.9243±0.037 • MRST01E= 0.94137±0.011 • Most uncertainties will go down with more data useful to constrain PDFs C. Issever
Z → μμ cross section (|η| < 1) using 337 pb-1 337pb-1 116 66 σ=261.2 ± 2.7 (stat) + 5.8 - 6.9 (sys) ± 15.1 (lum) pb NNLO @ 1.96 TeV Stirling, van Neerven σ(pp→Z)=251.3+-0.5(Th) C. Issever
Z →τeτh 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
Cross section summary new C. Issever
e+ W+ W+ W- proton anti-proton n yW antiproton proton W Charge Asymmetry Asymmetry in W production complicated by unknown n pz use lepton asymmetry: which convolves W production with V-A decay. C. Issever
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. C. Issever
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!! C. Issever
W charge asymmetry – new method Iterative procedure • Smaller statistical errors • Greater sensitivity • No additional systematics due to new method C. Issever
Jet Midpoint jet cross section Good agreement with NLO More details see talk of Olga Norniella in (HFS-5): Jets 1 C. Issever
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 C. Issever
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 → τeτh 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 !! C. Issever
Backup Slides C. Issever
W forward cross section C. Issever
Z → μμ cross section (|η| < 1) C. Issever
Z →τeτh 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 C. Issever
Z→ττ cross section C. Issever
Z→ττ cross section -- Systematics C. Issever
W Asymmetry – new method Leading order W production from Bo Young Han C. Issever
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 C. Issever
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 C. Issever
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 from Bo Young Han C. Issever
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) • PDF dependence from Bo Young Han C. Issever
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 C. Issever