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Elementary Particles

Elementary Particles. ~ Harris Chapter 11; plus some. ~ ER Chapter 18; yea, right. Rohlf: “Modern Physics from a to Z o ” www.pdg.lbl.gov Particle Adventure at http://pdg.lbl.gov/2005/html/outreach.html. OUTLINE. The Basics: Harris 11.4, 11.3

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Elementary Particles

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  1. Elementary Particles ~ Harris Chapter 11; plus some. ~ ER Chapter 18; yea, right. Rohlf: “Modern Physics from a to Zo” www.pdg.lbl.gov Particle Adventure at http://pdg.lbl.gov/2005/html/outreach.html

  2. OUTLINE • The Basics: Harris 11.4, 11.3 • Cross section calculation techniques: Harris 11.5 • Early proofs of quarks & gluons • QED (quantum electro dynamics) • QCD (quantum color dynamics) • QFD (quantum flavor dynamics) • Buzz Words & Unanswered Questions: Harris 11.6, 11.7 • CKM Matrix / Neutrino Oscillations • Unification • Parity & Time-Reversal Violation • the Higgs / where does mass come from?

  3. The basics • Equipment • Fundamental Objects • Fundamental Interactions

  4. Equipment e- • Electron Collider • DESY • Stanford • Proton Collider • FermiLab • CERN • Electron fixed target • Bates • CEBAF / JLab e+ p+ p- e- e-

  5. Fundamental Objects 3 generations 3 families 6 flavors leptons 3 generations 3 families 6 flavors quarks all spin ½ objects 0.511 MeV ~0 eV 105 MeV < 0.37 MeV 1784 MeV < 35 MeV ~350 MeV ~700 MeV 1500 MeV ~500 MeV 174000 MeV 4700 MeV

  6. Fundamental Objects 3 generations 3 families 6 flavors leptons 3 generations 3 families 6 flavors quarks Binding energy is a major effect proton = uud = 350 + 350 + 700 = 1400 >> true mass 938 MeV

  7. Fundamental Objects 3 generations 3 families 6 flavors leptons 3 generations 3 families 6 flavors quarks all spin ½ objects Electric charge of leptons Electric charge of quarks

  8. Fundamental Objects Field particles or gauge bosons 8 gluons (graviton) --- --- < 6E-17 eV 80, 91 GeV other required objects Higgs bosons LR bosons > 114 GeV > 715 GeV

  9. Fundamental Interactions a = (vertex fn)2

  10. Comments on Fundamental Interactions • Range • photons are ‘stable’  DE = 0  cDt = ∞ • IVB are ‘unstable’  DE ~ 2 GeV  cDt ~ 0.1 cm • gluons – no info • Electric Charge • all quarks and e m t and W± can participate in QED • since g has no charge, g cannot interact with g ‘s. • Color • only quarks & gluons have color  participate in QCD • Since g has color, g can interact with g‘s  “glueballs” • Flavor • all quarks and leptons have “flavor”, therefore can participate in QFD

  11. Composite Objects • Hadrons • mesons – qq • baryons – qqq • quaterions – not observed • pentaquarks – i.d.i. • .

  12. Cross Section Techniques Feymann diagrams

  13. How to calculate cross sections dI Io

  14. simplified* Feymann rules • Each vertex gives • QED: Ze • QCD: G • QFD: g • Each propagator gives • massless: • massive: momentum transfer energy of the compound state Eres = Eo + i G/2 * dropping various constants, spin-info, ... other details

  15. before after pf scattered particle pi incident particle qmomentum transfer pi = pf + q Eres = Eo + i G/2 lifetime total decay width

  16. SP333 or Time-Dep Perturb Th Example

  17. Nuclear Physics Example 2nd order perturb theory

  18. What makes us thinkquarks and gluonsexist? • 2 jet events • 3 jet events • R-ratio • Zo width

  19. CDF detector @ FermiLab http://www-cdf.fnal.gov/cdfphotos

  20. 2 Jet events TASSO / PETRA / DESY

  21. 3 Jet events

  22. R-ratio

  23. q- e- g e+ q+ R = m- e- g e+ m+

  24. If NRG available in reaction ~ 1000 MeV, then uds If NRG available in reaction ~ 3000 MeV, then udsc If NRG available in reaction ~ 10,000 MeV, then udscb If NRG available in reaction ~ 180,000 MeV, then udscbt

  25. RWB RYB RGB

  26. 3·R

  27. at available NRG = 90 GeV 3 generations -- the Zo width m- e- Zo e+ m+ total decay width • = Ge + Gve • + Gm + Gvm • + Gt + Gvt

  28. QED • Stationary States • Reactions

  29. QED - Stationary States Some kind of experiment to excite the system e p

  30. Note: even though we have quessed a good potential function, we realize that we will have to include s-o, rel KE, Darwin, Lamb shift, ... -- and the perturbations could have been big.

  31. QED - Reactions related to 2 vertices

  32. g e+ g e- e- e- arrows are added to help identify particles versus antiparticles e+ e- e+ e+ g g e- e+ e- e-

  33. In a real experiment: aEM ~ 1/137 e+ e+ e- e- s = + + aEM + + e+ e- (aEM)2 + ... + QED is renormalizable , higher order diagrams can be accounted for by choosing an effective value for ‘e’ QED cross sections are ‘easy’ to calculate.

  34. QCD • Stationary States • Reactions

  35. QCD - Stationary States

  36. confinement term ‘Coulomb’ term K1 ~ 50 MeVfm K2 ~ 1000 MeV/fm ? ? As a matter of fact, must have V  0 by about 1 fm.

  37. RUBBER BANDS stretch & break stretch 2 ends U = ½ k (Dx)2 4 ends QUARK PAIRS stretch & break the color field stretch

  38. QCD - Reactions K1 ~ 50 MeVfm K2 ~ 1000 MeV/fm At r ~ 0.5 fm, aQCD ~ 1.5

  39. How-To: quark-quark reactions meson ? meson ? spectator quarks Which pairs of quarks interacted?

  40. uG uR dR dG uR uG

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