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Exotica: Overview of the Searches for New Vector Boson High Mass States

Exotica: Overview of the Searches for New Vector Boson High Mass States. Cory Fantasia PY898 03/30/09. The Exotic:. Z ′ W ′ RS Graviton. 3 Particles. Z ′ W ′ RS Graviton. Z′ Models. Sequential Standard Model (SSM) Same Coupling Strength as SM Z Simplest extension of SM

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Exotica: Overview of the Searches for New Vector Boson High Mass States

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  1. Exotica: Overview of the Searches for New Vector Boson High Mass States Cory Fantasia PY898 03/30/09

  2. The Exotic: • Z′ • W′ • RS Graviton

  3. 3 Particles • Z′ • W′ • RS Graviton

  4. Z′ Models • Sequential Standard Model (SSM) • Same Coupling Strength as SM Z • Simplest extension of SM • Basis for this talk • Littlest Higgs • E6 and SO(10) Grand Unifying Theories • Kaluza-Klein Excitation of SM Z

  5. Z′ - Tevatron • Dilepton channel • Z′ → ee • Z′ → μμ • Z′ → ττ • Z′ → t tbar • With 450 pb-1 CDF limits SSM Z′ to 825 GeV • Dielectron / dimuon channels most powerful • Other models are less strict on mass

  6. Search Z′ → μμ • Channel will offer first glimpse of signal • Using first data assumptions • Misalignment • Larger uncertainties

  7. Decay Modes - Z′ • Z′ → ee • Z′ → μμ • Z′ → WW • Harder to utilize

  8. Background Z′ • Photons • Require track • QCD Jets • Require isolation • Require > 90% of energy to be in ECAL • Require hits in muon system • Require oppositely charged leptons • Drell-Yan (irreducible) – find mass peaks

  9. Discovery

  10. Z′ →WW • Peak resolution more difficult • Clearest channel • WW → eνjj • Allows for discrimination between two W’s • Aids in background suppression • Background • W + jets

  11. Discovery - Z′ → WW • Using Cuts • |η| < 2 for jets • ET of W > M(Z′)/3 • Reconstructed W’s good mass values (|diff| < 15) • Assumes coupling falls off like 1/m(Z′)2 • 300 fb-1

  12. 3 Particles • Z′ • W′ • RS Graviton

  13. W′ • Sequential Standard Model • Same couplings as W • Makes signal more difficult to extract • MET is now a factor

  14. W′ - Tevatron Results • Using W′ → eν or W′ → t bbar • Minimum mass set to 788 GeV using 205 inv pb-1 • Set with leptonic decays

  15. W′ → μ ν • Require single muon • Isolation • >13 hits along track • Largest source of background is SM W • Must use reconstructed mass peak

  16. Discovery • Discovery potential with 1 fb-1 up to 3.5 TeV

  17. W′ → e ν • Largest source of background comes from SM W decays • Use similar cuts to resolve mass peak • Isolated, tracked

  18. W′ → WZ → 3l + ν • Resolution (with no cuts) decreases with increasing mass • W′ still visible past 2 TeV with 300 fb-1 • W ′→ WZ → 3l + ν • Opposite signed leptons form Z • Leaves lepton + MET to form W

  19. Background • WZ → 3l + ν • Mass peak distinction • ZZ → 4l • 1 lepton missed (shows up as MET) • tt → Wb Wb • b quark yields a lepton plus 2 from W’s • b lepton won’t be isolated

  20. W′→ WZ Discovery • 300 fb-1 • Using worst case model to obtain 5 sigma assuming coupling falls off like 1/m(W′)2

  21. W′ (Higgsless) • W′ Z → WZZ → jj4l • Remove reconstructed Z mass (oppositely charged leptons) • Remaining WZ mass shows peak

  22. Cuts - W′ Z → WZZ → jj4l • Require large (>4) η separation between jets • Reduces gluon jet background • Ej > 300 GeV • pTj > 30 GeV • pTl > 10 GeV

  23. Discovery - Higgless • Larger cross section of WZjj offers chance of quicker discovery as the mass of the W′ increases

  24. 3 Particles • Z′ • W′ • RS Graviton

  25. RS Graviton • Motivation? • Explain Weakness of Gravity • Difference between Planck mass and TeV Scale • Unify Gravity with other forces

  26. Theory • Lisa Randall and Raman Sundrum • 15 Orders of Magnitude between Mplanck and TeV scale • Expand Universe to 5th Dimension • Scales ~ e-kπR • kR ~ 11 • k ≡ curvature of new dimension • R ≡ is the size of the dimension

  27. Theory • TeV Brane → Planck Brane • SM interactions exist on TeV Brane • Can propagate in 5-D • SM particles fixed between these branes • Since Higgs is on TeV Brane, the closer a SM particle lies to TeV Brane the larger its mass • “Naturally” form mass hierarchy

  28. Production • c ≡ k/Mplanck • Dominate factor is graviton interactions

  29. Discrimination – RS • Spin 2 particle • Different angular distribution • Use θ* • Angle between quark and lepton • G → ee • High energy electron jets

  30. End Caps are Critical for Discrimination

  31. Signal over Background • E > 100 GeV • Isolated • 2 Hit Track • > 90% of energy in ECAL

  32. Discovery CMS • c = 0.01 (green) • c = 0.02 (blue) • c = 0.05 (pink) • c = 0.1 (red) • With similar cuts • Isolated • High Energy

  33. Discovery CMS • Depending on the coupling parameter discovery could come with 1 fb-1

  34. Conclusions • Z′ muonic decay offers best hope seeing signal early • Subsequent use of electron decay for confirmation and refinement of signal • W′ searches will require more work • MET in the final state • RS Graviton offers exciting answers but will need a more careful analysis

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