1. From Electrons to Quarks - 2 l The Standard Model l …And Beyond

2. Electron – 1897 J.J Thomson Top quark 1995 A Century of Particle Physics

3. … And The Particle Zoo!  ±,  0, e,  ±, K ±, K 0 S, K 0 L,  0, p, n,  +,  0, , , …

4. u uu d dde b bb  c cc s ss  gggggggg  ZW+ e   Quarks Leptons +2/3-1/3 -1 0 I II III BosonsFermions The Standard Model H t tt W-

5. The Standard Model d u d Neutron Proton u d u Delta++ u u u

6. The Electromagnetic Force q2q2 q1q1 Electron Proton Photon

7. n Neutron nene Anti-electron neutrino W-W- The Weak Force Radioactive decay of the neutron e Electron Proton p

8. The Strong Force u u d d g Strong force caused by the exchange of gluons

9. The Standard Model Summary All known matter is of quarks and leptons that interact via one or more forces: Strength Gravity10 -39 Weak10 -5 Electromagnetic10 -2 Strong 1

10. The Mass Puzzle

11. Imagine a room full of physicists From L. Smith, Scientific American, July 2000

12. … and someone famous walks in…

13. … he attracts admirers, which makes it difficult for him to move… …he has acquired inertia, that is, mass!!

14. Now imagine that it’s only a rumor that he is about to arrive…

15. … physicists cluster together to discuss the rumor… … just as they did before, but minus the famous person

16. Mr Higgs Boson Professor Peter Higgs

17. …And Beyond

18. Fermilab

19. The Just-So Puzzle ParticleMass [MeV] electron 0.51 muon 105.65 tau 1776.99 u 2.25 d 5.00 s 95.00 c 1250.00 b 4200.00 t 170,900.00 Why is the neutron heavier than the proton? NucleonMass [MeV] __________________ N (u d d)939.6 P (d u u)938.3 __________________ 1.3 MeV

20. The Vacuum Energy Puzzle The Standard Model predicts the energy density of the vacuum is > 10 2 GeV/fm 3 According to observation, the energy density of the vacuum is < 10 -52 GeV/fm 3 Oops!

21. The Gravity Puzzle 10 -39 Why is gravity so weak?

22. Nature’s Big Clue The Fundamental Parameters of Nature hPlanck’s constant cSpeed of light in vacuum GNewton’s gravitational constant l p ~ 4 x 10 -35 m l p ~ 4 x 10 -35 m The Planck Length

23. Brane Worlds Our 3-dimensional world could be embedded within a higher dimensional space Perhaps ours is but one of numerous brane worlds

24. 2008 2008 The Era of the LHC The Era of the LHC Graviton Our world