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High Mass Higgs Boson at CDF: Trilepton Signature

High Mass Higgs Boson at CDF: Trilepton Signature. Jason Nett University of Wisconsin-Madison CDF Collaboration 15 February 2010. Higgs Physics Search. LEP ruled out SM Higgs for m H <114 Gev . “Low Mass SM Higgs” (114< m H <135 GeV ) search based on H b-quark jets.

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High Mass Higgs Boson at CDF: Trilepton Signature

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  1. High Mass Higgs Boson at CDF: Trilepton Signature Jason Nett University of Wisconsin-Madison CDF Collaboration 15 February 2010

  2. Higgs Physics Search • LEP ruled out SM Higgs for mH<114 Gev. • “Low Mass SM Higgs” (114<mH<135 GeV) search based on H b-quark jets. • “High Mass SM Higgs” (135<mH<200 GeV) search based on H WW. • 2-Leptons: Gluon Fusion • 3-Leptons: Associated Production

  3. High Mass Higgs Search at CDF • H WW search focused only on 2-lepton channels until now. • Most recent result of all CDF H WW group dilepton analyses with 4.8 fb-1. • Dilepton focus mostly on gluon fusion production • We now add 3-lepton channels • Expected Limit: 1.21 • Observed Limit: 1.23 This is what we’ll improve upon

  4. Trileptons (VH VWW) • 3-Lepton events: strong for WH and ZH, others negligible. • By σ∙B.R. argument: 3-lepton VH adds 5.7% acceptance compared to 2-lepton gg H. • 3-Lepton+ ET Signature keeps backgrounds low. Two regions: • WH WWW lν,lν,lν • ZH ZWW ll,lν,jet • Event Selection: • 1 Lepton w/ pT>20.0 GeV (“Transverse Momentum”) • 2 Leptons w/ pT>10.0 GeV • ET>10.0 GeV (“Missing Energy” from undetected neutrinos

  5. ZH Analysis & WH Analysis • 3-Lepton events divided into two categories: • “Z-Peak” (ZH Analysis): Among the three leptons, there exists a pair with • Inv. Mass [81.0, 101.0] GeV • Opposite electric charge • Same lepton flavor (both electron or both muon) • ZH Analysis • 96% ZH vs. 4% WH • Control: Njet=0 (lose 17% signal, 63% background) • WH Analysis • 77% WH vs. 23% ZH • Control: 10.0< ET <20.0(lose 4% signal, 66% background) • “Z-Peak Removed” (WH Analysis): All 3-Lepton events not meeting all Z-Peak criteria

  6. HWW Trilepton Backgrounds • Signal Region: • WZ: Dominant, 3 Real Leptons • ZZ: 4-Lepton process, one lost • Zγ: Drell-Yan+photon, 2 Real Leptons+photonconvertion • tt: 2 Real Lepton + 1 faked (lepton-like signature) from b-jets • Fakes: Data-based estimate of 2 real leptons+1 faked lepton from jets.

  7. ZH:Discriminating Variables • ZH Analysis • Lead Jet ET: One of the Higgs-W-bosons decays hadronically, giving a high energy jet. • HT: 3 leptons from vector bosons, leptonic W decay gives neutrino, hadronic W decay give jets.

  8. WH:Discriminating Variables • WH Analysis • ΔR: Scalar Higgs decays to W’s, decaying leptonicallyw/ opposite spins, W-leptons have close angle. • ET: 3 W-bosons decay leptonically, so 3 neutrinos, so high missing energy.

  9. Neural Net Results (w/ NeuroBayes Package) ZH Analysis WH Analysis

  10. TrileptonLimits • ZH Analysis • Expected: 12.6 • Observed: 15.8 • WH Analysis • Expected: 8.86 • Observed: 11.0 Combined • What are Confidence Level Limit Plots? • Based in Poisson Statistics: • Small probabilities • Occurrences are independent • Prob. of occurrence remains constant • Expected Limits: Value of 1.0 indicates half of experiments will rule out SM Higgs at 95% C.L. if it doesn’t exist. • Observed Limits: Value of 1.0 indicates 5% of experiments would incorrectly exclude SM Higgs, assuming it does exist. • Expected Limit: 6.31 • Observed Limit: 7.61

  11. HWW Combined Limits • Expected Limit: 1.21 1.15 • Observed Limit: 1.23 1.08

  12. Conclusions • Associated SM Higgs Boson production (ZH & WH) is sensitive in 3-lepton events for the high mass search. • expected limits improve 6% • observed limits improve 15% • trileptonanalyses provide new constraints on dilepton backgrounds and vice versa. • Update from 4.8 to 5.3 fb-1 to be released shortly. • Side Project in Progress: Measure WZ becausehasn’t been done since 1.1 fb-1—we now have 5.3 fb-1 • CDF Higgs search very close to SM sensitivity at ~165 GeV.

  13. BACK UP

  14. Most Recent Tevatron Limits 95% C.L. Exclusion from 163-166 GeV (6 Nov. 2009)

  15. Systematic Errors

  16. HWW Trilepton Backgrounds • Control Region: • ZH Control: dominated by WZ • WH Control: dominated by Zγ • Both control regions agree with data very well.

  17. ZH Trilepton Analysis Neural Net Scores

  18. ZH Trilepton Neural Net

  19. ZH Trilepton Neural Net

  20. ZH Trilepton Neural Net

  21. ZH Trilepton Neural Net

  22. ZH Trilepton Neural Net

  23. ZH Trilepton Neural Net

  24. ZH Trilepton Neural Net

  25. WH Trilepton Analysis Neural Net Scores

  26. WH Trilepton Neural Net

  27. WH Trilepton Neural Net

  28. WH Trilepton Neural Net

  29. WH Trilepton Neural Net

  30. WH Trilepton Neural Net

  31. WH Trilepton Neural Net

  32. WH Trilepton Neural Net

  33. ZH Trilepton Analysis Discriminating Variables (ordered roughly by significance)

  34. ZH Discriminating Variables

  35. ZH Discriminating Variables

  36. ZH Discriminating Variables

  37. ZH Discriminating Variables

  38. ZH Discriminating Variables

  39. ZH Discriminating Variables

  40. ZH Discriminating Variables

  41. ZH Discriminating Variables

  42. WH Trilepton Analysis Discriminating Variables (ordered roughly by significance)

  43. WH Discriminating Variables

  44. WH Discriminating Variables

  45. WH Discriminating Variables

  46. WH Discriminating Variables

  47. WH Discriminating Variables

  48. WH Discriminating Variables

  49. WH Discriminating Variables

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