Electroweak Physics at the Tevatron

1. Adam Lyon / Fermilab for the DØ and CDF collaborations 15th Topical Conference on Hadron Collider Physics June 2004 Electroweak Physics at the Tevatron • Outline • Importance • Methodology • Single Boson Measurements • Summary & Outlook • W/Z+g and Diboson Results up next

2. mW , mt , and mH are related Constrain Higgs mass Test of standard model couplings (and see M. Kirby's talk) Study higher order QCD Many uses in detector studies and luminosity determination Learning from Electroweak Physics

3. Uncertainties in mW • Run 1 uncertainties (from hep-ex/0311039) • Uncorrelated uncertainties scale with luminosity • Correlated systematics improve as theory improves • Perhaps can reach 40 MeV/c2 per channel & exp with 2 fb-1

4. Collider: Tevatron for Run II Base goal is 4.4 fb-1(Design is 8.5 fb-1) by end of FY09

5. Saved from Run I Solenoid Central Calorimeter Central Muon System New/Improved in Run II 8 layer Si tracking (|h| < 2) Central Outer Tracker (|h| < 1) Plug Calorimeter (1.0 < |h| < 3.6) Extended muon coverage to |h| < 1.5 New and improved trigger and DAQ Luminosity ~400 pb-1 on tape Analyses shown here use 65 - 200 pb-1 Detectors: CDF

6. Detectors: DØ • Saved from Run I • Hermetic LAr Calorimeter • Muon Toroid and proportional drifttubes • New in Run II • 2T Superconducting Solenoid • Inner Tracker (Si Microstrips and Scintillating Fiber tracker) • Preshower detectors • Upgraded muon system (including better shielding) • New and improved trigger and DAQ

7. Luminosity370 pb-1on tapeAnalysis here use17-162 pb-1 Detectors: DØ

8. Use clean leptonic decays W (energetic lepton + ET) Z0 (energetic opposite sign leptons) W/Z Production and Event Topology

9. W and Z events are extremely useful • Measure cross sections • Calibration of detectors, luminosity measurements • Lepton universality, W width • Measure W and Z properties (pT(W), pT(Z), y(Z), lepton angular distributions) • Constrain PDFs, fit for couplings, look for new resonances • Measure W mT , lepton pTspectra • Yields mW , W width • W/Z + Jets • Backgrounds to Higgs and Top analyses • W/Z + g , Dibosons • Probe electroweak gauge structure • Backgrounds to New Phenomena searches

10. Both DØ and CDF follow similar strategies Triggers: Calorimeter triggers for electrons Track triggers for muons Selection: W - a lepton and large missing transverse energy Z - two opposite charge leptons Electron requirements: Isolated EM cluster Shower shape (CDF uses shower max, DØ has finely segmented calorimeter) Track pointing to calorimeter EM cluster Muon requirements: Track matched to calorimeter MIP trace and/or muon system track Reject cosmics by timing and impact parameter Track and calorimeter isolation Measure identification efficiencies with Z events Measure backgrounds with QCD Dijet events Systematics Luminosity (~6%) PDF (use CTEQ6 and MRST) (1-2%) Lepton ID (~1%) Backgrounds, E scale, Recoil model, Detector Description Analysis Methodologies

11. 2 EM objects withpT > 25 GeV/c CDF: central + plug cal (|h|< 2.8) DØ: central only Small backgrounds QCD Ztt CDF: DØ: Z  ee Cross Section

12. pTcut lowered to 15-20 GeV/c for muons DØ efficient for mmm> 30 GeV/c2 DØ applies a Drell-Yan correction Very small backgrounds:QCD (b-jets), Z  tt CDF: DØ: Z  mmCross Section

13. Requirements: 1 electron with ET > 25 GeV ET> 25 GeV(CDF plug analysis used 20 GeV) CDF: central & plug DØ requires |h| < 1.1 Track match required Backgrounds QCD, Z  ee, W  tn W  en Cross Section

14. W  en Cross Section CDF (central): CDF (plug): DØ:

15. Require m pT, ET > 20 GeV Backgrounds: QCD (b-jets), Z  mm, W  tn W  mnCross Section CDF: DØ:

16. Cross section comparisons * Track match required • CDF and DØ are rather similar, except in angular coverage • CDF uses plug calorimeter for far e coverage • DØ uses forward muon system for far m coverage

17. Infer the W width (Preliminary) • Use measured W and Z cross sections and R • Measured (CDF Preliminary) • Theory (NNLO, PDG) • LEP

18. Reconstructing t leptons is challenging Must use hadronic decays for ID (1 or 3 charged tracks plus p0's) But these are hadronic jets; high QCD background Look for tracks in a narrow 10° cone pointing toward a narrow calorimeter cluster Require 30° cone isolation for tracks Reconstruct p0's (in shower max for CDF) Require effective mass of tracks and p0's to be < 1.8 GeV/c2(mt+ resolution) Analyses with Taus

19. Start with track + ETtrigger Require t ET> 25 GeV, ET> 25 GeV No other jets above 5 GeV 2345 candidates in 72 pb-1 Bkg = 612  61 events e( ID)· A = 1.06  0.064 % W  tn (CDF Run II Preliminary)

20. Look for 1-prong decays Look for other t via e or m Understand tau ID Important for searches Proof of principle that ttresonances are seen at the Tevatron Z tt CDF:

21. Charge asymmetry in W  en • Goal is to improve understanding of PDFs using W charge asymmetry • Since u quarks on average carry more of the p momentum than d quarks, • W +produced in ud  W +are boosted along p • W -produced in du  W -are boosted along p • The e from the W decay carries information on the W direction, but true W direction cannot be reconstructed due to unmeasured pzof n • Use the edirection to measure AyWconvoluted with V-A decay distribution • Results are sensitive to ratio of PDFs for u and d • Do for low and high ET [NEW APPROACH](at higher e ET, e dir is closer to W dir; less cancellation with V-A) • Sensitivity is best at high |h| where it is least constrained

22. Require eET and ET > 25 GeV 50 < mT < 100GeV No other EM object with ET > 25 GeV In forward region, use "calorimeter seeded Si tracking" to utilize new forward Silicon This along with drift chamber can determine charge within |h| < 2 Measure charge mis-id rate with data using Zs < ~1% within |h| < 1.5 < ~4% far forward Backgrounds Z [MC], W  tn [MC],QCD [data] Charge asymmetry in W  en

23. Interference of g* and Zf = u, d, e Leads to AFBin Depends on uuZ, ddZ and eeZ couplings Can probe couplings Near the Z resonance, AFBis related to sin2 qW New interactions may modify the SM AFB prediction Drell-Yan Forward Backward Asymmetry f ’ f ’ f f g* Z + f f f ’ f ’ e- q q q e+

24. Require 2 isolated electrons with pT > 20 GeV/c 5211 candidates in 72 pb-1 No asymmetry seen in dijet background Use Collins-Soper reference frame for measuring electron scattering angle Reduces uncertainty in scattering angle due to pTof incoming partons Drell-Yan Forward Backward AsymmetryCDF Run II Preliminary

25. Drell-Yan Forward Backward AsymmetryCDF Run II Preliminary • Fit for weak mixing angle • Fits for couplings are in good agreement with world averages • No evidence of new interactions above the Z pole

26. High Mass Drell-Yan Spectrum • Sensitive to new physics • New gauge bosons (e.g. Z'), extra dimensions • Run 1 limits surpassed and new models explored

27. Summary • Current preliminary results consistent with SM • (Theory lines NNLO from Hamberg, van Neerven, Matsuura)

28. Outlook • 1.96 TeV cross sections nearing publication • Tevatron electroweak working group will make combinations • Stay tuned for further analyses; > 300 pb-1 on tape • Preliminary W mass measurements soon

29. EXTRAS

30. Z  ee Cross Section

31. Afb Acceptance

32. Uncorrected Afb