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Electroweak Physics Results from the Tevatron

Electroweak Physics Results from the Tevatron. Breese Quinn University of Mississippi On behalf of the CDF and DØ Collaborations. 2012 Aspen Winter Conference on Particle Physics February 12, 2012. Why W’s and Z’s?. Simple signatures Isolated lepton(s) { W ( Z )} Missing E T { W}

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Electroweak Physics Results from the Tevatron

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  1. Electroweak Physics Results from the Tevatron Breese QuinnUniversity of MississippiOn behalf of the CDF and DØ Collaborations 2012 Aspen Winter Conference on Particle PhysicsFebruary 12, 2012

  2. Why W’s and Z’s? • Simple signatures • Isolated lepton(s) {W(Z)} • Missing ET {W} • Little recoil/underlying evt • Well-understood physics • Calibrating detectors • Precision SM measurements • Deviations from SM • Backgrounds to and “proof-of-principle” for Higgs searches W Z } } B. Quinn University of Mississippi

  3. W / Z • Leads to final states: l (from W) or ll /(from Z) • Produced by • SM: ISR FSR • Non-SM Triple Gauge Couplings FSR Cut on Mll to eliminate FSR events B. Quinn University of Mississippi

  4. W : DØ • Additional cuts to remove FSR and • PRL 107, 241803 (2011) B. Quinn University of Mississippi

  5. Z : DØ • PRD, accepted 1/9/12, arXiv:1111.3684 B. Quinn University of Mississippi

  6. Z : CDF • Includes Z decay channels Z→ll ( ) Z→ ( ) • Higher photon energy cuts to optimize limit setting • PRL 106, 051802 (2011) • BSM difference mainly off scale above 200 GeV where there is no data B. Quinn University of Mississippi

  7. WW/WZ : CDF • CDF found a 4.1 excess in WW/WZ events peaked in excl. Wjj final state at Mjj=147 GeV • DØ closely reproduced the CDF analysis • PRL 106, 171801 (2011) – 4.3 fb-1 • PRL 107, 011804 (2011) B. Quinn University of Mississippi

  8. WW/WZ : DØ • DØ has also produced a new (WW+WZ) measurement with this data set • Uses a Random Forest MVA to extract the signal • Assume SM (WW)/(WZ) when fitting RF output for (WV) • Then fit (WW) and (WZ) simultaneously, allowing both to float • Cross check with fit to Mjj • PRL, submitted 12/5/11 arXiv:1112.0536 B. Quinn University of Mississippi

  9. WZ : CDF • 3 lepton + Missing Et signature • BG to H→WW trilepton search • Largest BG is ZZ→llll, with one lmis-ID • Reduced with new cut of trilepton+track (pt > 8 GeV) events • Uses NeuroBayes NN to extract signal • CDF Note 10176 B. Quinn University of Mississippi

  10. WZ : CDF • final state is sensitive to TGC through tree level s-channel • Measured by analyzing Z pt distribution • CDF Note 10595 B. Quinn University of Mississippi

  11. ZZ : DØ • BG to H→ZZ • ZZ→llll final state • Obs10 evts (Exp: 8.7 sig + 0.4 bg) • Combined with previous ZZ→ll 2.7 fb-1 result for ZZ→ll total (ZZ) • PRD 84, 011103 (2011) B. Quinn University of Mississippi

  12. ZZ : CDF ZZ→ll • NeuroBayes NN ZZ→llll • Obs 14 evts (Exp: 9.5 sig + 0.3 bg) • PRL, accepted 1/30/12 arXiv:1112.2978 B. Quinn University of Mississippi

  13. WZ/ZZ : DØ – NEW! • Look at leptonic final states: WZ→lll , ZZ→ll • Looser trigger requirements than previous analyses to maximize yields • PRD, submitted 1/30/12 arXiv:1201.5652 B. Quinn University of Mississippi

  14. Z/* PT Distribution : CDF – NEW! • Measurement of in • 66 GeV < Mee < 116 Gev • All boson rapidity and decay electron phase space • Careful acceptance corrections by tuning simulations to match data • e.g. correction to PT distribution • CDF Note 10699 B. Quinn University of Mississippi

  15. Z/* Angular Coefficients : CDF • Study angular distribution of electron pairs in • Xis a final state q or g which imparts transverse momentum to the Zthrough annihilation or Compton scattering • Angular distribution of lepton decay in the Collins-Soper frame is • pQCD predicts different relations and Z pTdependencies for the coefficients 2.1 fb-1 B. Quinn University of Mississippi

  16. Z/* Angular Coefficients : CDF A0and A2 • Should be the same for Z and *, but distinct Z pTdependencies for annihilation and Compton • Reveals relative contributions of the two Z production processes • Lam-Tung relation states that A0 = A2at LO, and nearly so at all orders, but only for spin-1 gluons • Lam-Tung badly broken for scalar g • Indirect confirmation of vector g B. Quinn University of Mississippi

  17. Z/* Angular Coefficients : CDF A3and A4 • Originate from Z/* interference • Should be nearly flat inZ pT • AFB A4 • Sensitive to Weinberg angle, • PRL 106, 241801 (2011) B. Quinn University of Mississippi

  18. Z/* Forward-Backward Asymmetry : DØ • Vector and axial vector coupling involved in • Results in forward-backward asymmetry, AFB , of final state electrons • A , B functions of A4 from Z/*ang.Coeff. both *-f and Z-f coupling only Z-f coupling FORWARD e+ p e- Collins-Soper Frame B. Quinn University of Mississippi

  19. Z/* Forward-Backward Asymmetry : DØ • At high mass, above Z pole, AFB is dominated by Z/* interference → sensitive to new physics • Extract sin2eff from shape of AFB distribution A4 (CDF) 0.2329 ±0.0012 B. Quinn University of Mississippi

  20. Z/* Forward-Backward Asymmetry : DØ • Make 4D fits of Z-light quark vector and axial coupling to AFB templates from theory • Most precise measurement • PRD 84, 012007 (2011) B. Quinn University of Mississippi

  21. Summary • The Tevatron experiments have already had a remarkably productive program of EW measurements … so far! • Given us a greater understanding of particle physics • High precision measurements of SM parameters • First observations of several new EW processes and phenomena • Enabled Higgs searches by characterizing important backgrounds, and proving we can measure Higgs-type final states and cross sections • No measurements to this point have used the full Tevatron dataset – many less than half • Additional important results coming very soon! B. Quinn University of Mississippi

  22. Backup Slides B. Quinn University of Mississippi

  23. Triple Gauge Couplings • Charged • Neutral B. Quinn University of Mississippi

  24. WjjExcess Exclusion Levels : DØ B. Quinn University of Mississippi

  25. W Mass : • In the SM, MW related to other observables through • Radiative corrections, r • Constrain SM MH with precision measurements of Mt , MW • But MW is the more powerful handle! B. Quinn University of Mississippi

  26. W Mass : • Measure two things in W→ev events: • Electron – to ~10-4 • Recoil – to ~10-2 • Calibrate with large Z sample B. Quinn University of Mississippi

  27. W Mass : • Measure the mass by template fitting in different variables B. Quinn University of Mississippi

  28. W Mass : • Light Higgs is favored by EW fits • Too light? Central value of 92 GeV already in directly excluded region • EW fits exclude Higgs above 161 GeV • For MW→15 MeV , Mt: →1 MeV and central values remain the same • MH= 71 GeV most probable • Higgs excluded above 117 • Rule out SM Higgs • P. Renton ICHEP 2008 B. Quinn University of Mississippi

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