W Boson Physics at Fermilab

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W Boson Physics at Fermilab

• Michael Kirby
• Duke University
• March 8, 1999

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Outline

• Standard Model, Breaking Things
• Boson Couplings, Trilinear Effects
• Fermilab, CDF, Big Toys
• Tevatron
• Detectors
• Confirmation of Electroweak Unification

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Why study particle physics?

• Searching for fundamental particles
• Democretus idea of unbreakable building block
• Explores unnatural regions
• Enjoy breaking things! (i.e. the Standard Model)

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Standard Model
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Construction of particles

• Baryons

• Mesons

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Force Propagators
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Conservation Laws

• Energy, Momentum, Angular Momentum
• Lepton Number Conservation
• Strong and Electromagnetic
• Baryon Number
• EM -gt Electron-Proton Binding in Atom
• Strong -gt Quark Binding in Proton
• Weak -gt Change quark flavor
• Neutron Decay

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Feynman Diagrams
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Standard Model Lagrangian

• Electromagnetic Theory U(1) (QED)
• No Boson Interactions
• Standard Model SU(3)XSU(2)XU(1)
• ElectroWeak SU(2)XU(1)
• Non-Abelian Group
• Leads to TriLinear Boson Coupling
• WW?,WWZ,ZWW

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Boson Couplings

• In U(1) Photon coupling not permitted
• Electroweak Contains TriLinear Coupling

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Fermilab Proton-Anitproton Collider
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Tevatron

• ?s 1.8 Tev
• Luminosity -gt 7 x 10³º cm ² s ¹
• Bunch spacing 3.5 µs
• Upgrades
• ?s 2.0 Tev
• Increased Luminosity 5 x 10 ³² cm ² s ¹
• 132 ns bunch spacing

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CDF Upgrades

• Tracking System
• SVX II
• New Intermediate Silicon
• New Central outer tracker
• Intermediate Muon Detectors
• New End Plug Calorimeters
• Electronics Upgrades

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Analysis of TriLinear Gauge Boson Coupling

• J. Ellison and J. Wudka, Univ of California
• From 67 pb ¹ integrated luminosity
• 70,000 W events total
• Standard Model Monte Carlo predicts 75 events
  matching T3 coupling

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Leading Order Feynman Diagram of T3 Coupling
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TriLinear Lagrangian Term
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WW? Signature
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Background

• W jets
• jet -gt ?º -gt photon pair
• get probability from other multi-jet samples
• Z? -gt l l ?
• W(??)?
• ? -gt l??
• Modeled in Monte Carlo
• W jets dominates

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W? Events Observed
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?k? and ?? Analysis

• Subtracting Predicted Background gives matching
  signal with SM
• Use binned maximum likelihood fit to photon pt
  distribution
• Combined limits
• -0.93 lt ?k? lt 0.94 (for ?? 0)
• -0.31 lt ?? lt 0.29 (for ?k? 0)

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WW? Coupling Limits
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Conclusions

• Rules out U(1) as only photon Coupling
• SU(2)XU(1) Electroweak gives consistent results
• Upgrades will improve physics
• More data and greater statistics
• More exotics with increased luminosity
• Easier to Break Things!