1. Future Colliders: Opening Windows on the World Young-Kee Kim The University of Chicago ICFA Seminar September 28 - October 1, 2005 Kyungpook National University, Daegu, Korea

2. Welcome to Korea Calligraphy by my father

3. Accelerators are Powerful Microscopes. They make high energy particle beams that allow us to see small things. seen by high energy beam (better resolution) seen by low energy beam (poorer resolution)

4. Accelerators are also Time Machines. E = mc 2 They make particles last seen in the earliest moments of the universe. Energy Particle and anti-particle annihilate. particle beam energy anti-particle beam energy

5. Accelerators powerful tools! PEP-II, SLAC, Palo Alto, USA HERA, DESY, Hamburg, Germany KEKb, KEK, Tsukuba, Japan Tevatron, Fermilab, Chicago, USA

6. 1929 Ernest Lawrence (1901 - 1958) 3/4 of century later Tevatron at Fermilab x10 4 bigger, x10 6 higher energy Today Many generations of Accelerators created with higher and higher energy given to the beam particle CDF ~1500 Scientists D0

7. With advances in accelerators, we discovered many surprises. Our field has been tremendously successful in creating and establishing “Standard Model of Particle Physics” answering ”what the universe is made of” and “how it works” Energy Luminosity (Collision Rate) Time

8. ~90 years ago 1 10,000 ~60 years ago 1 10 ~40 years ago 1 100,000 Present What is the universe made of? electron up quark down quark atom nucleus proton neutron 1 100,000 of human hair Rutherford

9. Everything is made of electrons, up quarks and down quarks. Are electrons, up and down quarks the smallest things? Are they made of even smaller things?

10. top quark anti-top quark Z W +, W -.. e   e -      u d s c b  gluons Elementary Particles and Masses e   e +      u d s c b - - - - (Mass proportional to area shown but all sizes still < 10 -19 m) Why are there so many? Where does mass come from?

11. Gravitational Force Electromagnetic Force Issac Newton (1642 - 1727) James Clerk Maxwell (1831 - 1879) What holds the world together? Beginnings of Unification

12. Einstein tried to unify electromagnetism and gravity but he failed. Unification of Gravity and Electromagnetism?

13. radioactive decays holding proton, nucleus gluons Weak Force Strong Force Enrico Fermi (1901 - 1954) 1 fm = 10 -15 m

14. Dream of Unification continues! We believe that there is an underlying simplicity behind vast phenomena in nature. Do all the forces become one? At high energy, do forces start to behave the same as if there is just one force, not several forces? Extra hidden dimensions in space?

15. Particle Physics & Cosmology Questions from Astrophysical Observations

16. Everything is made of electrons, up quarks and down quarks. Galaxies are held together by mass far bigger (x5) than all stars combined. Dark Matter - What is it? Everything that we can see

17. particles anti-particles particles Accelerators Where did all antimatter go? Big Bang Inflation Create particles & antiparticles that existed ~0.001 ns after Big Bang E = mc 2

18. Matter and Anti-Matter Asymmetry (CP Violation) Belle at KEK in Japan and BaBar at SLAC in US discovered CP violation in the B system. From their subsequent precision measurements of CP violation we know now that there must be new physics with CP violation in order to explain matter and anti-matter asymmetry in the universe. Belle BaBar

19. Not only is the Universe expanding, it is Accelerating!! Where does energy come from? Dark Energy

20. What is the world made of? What holds the world together? Where did we come from? Primitive Thinker

21. 1. Are there undiscovered principles of nature: New symmetries, new physical laws? 2. How can we solve the mystery of dark energy? 3. Are there extra dimensions of space? 4. Do all the forces become one? 5. Why are there so many kinds of particles? 6. What is dark matter? How can we make it in the laboratory? 7. What are neutrinos telling us? 8. How did the universe come to be? 9. What happened to the antimatter? Evolved Thinker From “Quantum Universe”

22. Answering the Questions with Next Generation of Accelerators (Colliders)

23. e + e - e-proton proton-proton today 1970 1980 1990 2000 2010 2020 2030 LHC ILC TEVATRON HERA LEP,SLC PEP-II, KEKB VEPP, CLEO-c, BEPC DA  NE FNAL, CERN, J-PARC Energy Frontier Colliders: Flavor Specific Accelerators: e + e - (b factory) e + e - (c factory) e + e - (s factory) CLIC  Collider LHCb

24. x x x xx x x xx x xx x Electron Z,W Boson Top Quark Origin of Mass: There might be something (new particle?!) in the universe that gives mass to particles Nothing in the universe Something in the universe Higgs Particles: Coupling strength to Higgs is proportional to mass

25. M top (GeV) W Z W, Z top bottom top Higgs Tevatron: Improve Higgs Mass Pred. via Quantum Corrections Tevatron Run II Current precision measurements favor light Higgs: < ~200 GeV. M W (GeV)

26. Tevatron: Improve Higgs Mass Pred. via Quantum Corrections M top (GeV) M W (GeV) LHC: Designed to discover Higgs with M higgs = 100 ~ 800 GeV M  (GeV) 130 GeV Higgs L = 100 fb -1 # of events / 0.5 GeV

27. Tevatron: Improve Higgs Mass Pred. via Quantum Corrections LHC: Designed to discover Higgs with M higgs = 100 ~ 800 GeV M Higgs (GeV) 5  Discovery Luminosity (fb -1 ) M top (GeV) M W (GeV)

28. Tevatron: Improve Higgs Mass Pred. via Quantum Corrections LHC: Designed to discover Higgs with M higgs = 100 ~ 800 GeV Will the Tevatron’s prediction agree with what LHC sees? 5  Discovery / Luminosity (fb -1 ) M Higgs (GeV) 5  Discovery Luminosity (fb -1 ) easy hard M top (GeV) M W (GeV)

29. 115 GeV Higgs is an interesting case! LEP Saw a 2  hint Tevatron 2007 (2.5 fb -1 / expt) 95% CL Limit Tevatron 2009 (8 fb -1 / expt) WH  Wbb ZH  Zbb 75% chance for 3  evidence 10% chance for 5  discovery LHC H   ttH  ttbb qqH  qq  (forward qq jets) But, Higgs sector may be very complex. New physics models expect multiple Higgs particles. Higgs WZWZ WZWZ d u e+e+ e-e- Z Z LEP Tevatron LHC

30. Supersymmetric Extension of Standard Model (SUSY) e+ e- superparticle e ~ e spin 1/2 spin 0 M e ≠ M e Symmetry between fermions (matter) and bosons (forces) “Undiscovered new symmetry” SUSY solves SM problems: e.g. divergence of Higgs mass, unification. SUSY provides a candidate particle for Dark Matter, solution to matter- antimatter asymmetry, possible connection to Dark Energy? If m super particle < ~1 TeV, fermion and boson loops cancel and Higgs mass becomes stable. particle super particle Higgs Mass: ~

31. Higgs in Minimal Supersymmetric Extension of Standard Model tan  M A (GeV) M top (GeV) MSSM M W (GeV) Tevatron LHC ILC LHC LHC will be the best place to discover Higgs particles!

32. If we discover a “Higgs-like” particle, is it alone responsible for giving mass to W, Z, fermions? Experimenters must precisely measure the properties of the Higgs particle without invoking theoretical assumptions.

33. proton proton (anti-proton!) e - e + elementary particles well-defined energy and angular momentum uses its full energy can capture nearly full information LHC: ILC:

34. ILC can observe Higgs no matter how it decays! 100 120 140 160 Recoil Mass (GeV) M Higgs = 120 GeV Number of Events / 1.5 GeV Only possible at the ILC ILC simulation for e + e -  Z + Higgs with Z  2 b’s, and Higgs  invisible

35. Coupling Strength to Higgs Particle Mass (GeV) Standard Model Coupling ∞ particle mass ILC experiments will have the unique ability to make model-independent tests of Higgs couplings to other particles, at the percent level of accuracy Standard Model Coupling ∞ particle mass LEP e + e - collider Coupling Strength to Z boson e : 0.1%  : 0.1%  : 0.1% : 0.2% q : 0.1% (PDG values) This sensitivity is sufficient to discover extra dimensions, SUSY, sources of CP violation, or other novel phenomena.

36. The Higgs is Different! All the matter particles are spin-1/2 fermions. All the force carriers are spin-1 bosons. Higgs particles are spin-0 bosons. The Higgs is neither matter nor force; The Higgs is just different. This would be the first fundamental scalar ever discovered. The Higgs field is thought to fill the entire universe. Could give some handle of dark energy(scalar field)? Many modern theories predict other scalar particles like the Higgs. Why, after all, should the Higgs be the only one of its kind? Once nature learns how to do something, she does it again! ILC can search for new scalars with precision.

37. HIGGS If discovered, the Higgs is a very powerful probe of new physics. Hadron collider(s) will discover the Higgs. ILC will use the Higgs as a window viewing the unknown.

38. Unification We want to believe that there was just one force after the Big Bang. As the universe cooled down, the single force split into the four that we know today. 1TeV = 10 3 GeV (10 16 K) 10 -11 s 10 16 GeV (10 29 K) 10 -38 s 10 19 GeV (10 32 K) 10 -41 s 2.3 x 10 -13 GeV (2.7K) 12x10 9 y Energy Temp Time

39. Unification of electromagnetic & weak forces (electroweak theory) Long term goal since 60’s We are getting there. Beautifully demonstrated at HERA ep Collider at DESY The main missing link is Higgs boson HERA Q 2 [GeV 2 ] Electromagnetic Force Weak Force f  HERA: H1 + ZEUS

40. Higher energy, Shorter distance Stronger force

41.   -1   -1   -1 10 4 10 8 10 12 10 16 10 20 Q [GeV] 60 40 20 0  -1 13 orders of magnitude higher energy The Standard Model fails to unify the strong and electroweak forces.

42. Adding super-partners

43. 10 4 10 8 10 12 10 16 10 20 Q [GeV] 60 40 20 0  -1   -1   -1   -1 With SUSY But details count! Precision measurements are crucial.

44. Energy (GeV) Masses also evolve with energy and matter unifies at high energies. ILC ability in measuring SUSY parameters accurately is crucial to extract mass evolution. Discovering Matter Unification in Supersymmetry Energy (TeV) Mass Squared

45. With SUSY Unifying gravity to the other 3 is accomplished by String theory. String theory predicts extra hidden dimensions in space beyond the three we sense daily. Can we observe or feel them? too small? Other models predict large extra dimensions: large enough to observe up to multi TeV scale.

46. Large Extra Dimensions of Space LHC can discover partner towers up to a given energy scale. ILC can identify the size, shape and # of extra dimensions. qq,gg  G N  e + e -,  +  - M ee,  [GeV] LHC M ee [GeV] DZero Tevatron GNGN qqqq e+e-e+e- Tevatron Sensitivity 2.4 TeV @95% CL Collision Energy [GeV] Graviton disappears into the ED Production Rate ILC GNGN e+e-e+e-   M ee [GeV] Events / 50 GeV / 100 fb -1 10 2 10 1 10 -1 10 -2 LHC

47. New forces of nature  new gauge boson LHC has great discovery potential for multi TeV Z’. Using polarized e +, e - beams, and measuring angular distribution of leptons, ILC can measure Z’ couplings to leptons and discriminate the origins of the new force. M ee [GeV] M  [GeV] Vector Coupling Axial Coupling Related to origin of  masses Related to origin of Higgs Related to Extra dimensions Tevatron LHC ILC 10 4 10 3 10 2 10 1 10 -1 Events/2GeV qq  Z’  e + e - Tevatron sensitivity ~1 TeV CDF Preliminary

48. Dark Matter (What is the role of Dark Matter in galaxy formation and shapes?) a common bond between astronomers, astrophysicists, and particle physicists Astronomers & astrophysicists over the next two decades using powerful new telescopes will tell us how dark matter has shaped the stars and galaxies we see in the night sky. Only particle accelerators can produce dark matter in the laboratory and understand exactly what it is. The ILC may be a perfect machine to study dark matter.

49. Dark Matter in the Lab Underground experiments (CDMS) may detect Dark Matter candidates (WIMPS) from the galactic halo via impact on colliding DM particle on nuclei. Dark Matter Mass [GeV] 10 -44 10 43 10 -24 10 100 1000 Interaction Strengh [cm 2 ] LHC may find DM particles (a SUSY particle) through missing energy analyses. (LHC is the best place to discover many of SUSY particles)

50. The ILC can determine its properties with extreme detail, allowing to compute which fraction of the total DM density of the universe it makes. Dark Matter Mass from Supersymmetry (GeV) Fraction of Dark Matter Density

51. Particles Tell Stories! The discovery of a new particle is often the opening chapter revealing unexpected features of our universe. Particles are messengers telling a profound story about nature and laws of nature in microscopic world. The role of physicists is to find the particles and to listen to their stories.

52. Discovering a new particle is Exciting! Top quark event recorded early 90’s We are listening to the story that top quarks are telling us: Story is consistent with our understanding of the standard model so far. But why is the mass so large? We are now searching for a story we have not heard before. M top world = 172.7 ± 2.9 GeV

53. We are hoping in the next ~5 years LHC will discover Higgs. ILC will allow us to listen very carefully to Higgs. This will open windows for discovering new laws of nature. Discovering “laws of nature” is even more Exciting!! This saga continues…. There might be supersymmetric partners, dark matter, another force carrier, large extra dimensions, …… for other new laws of nature. Whatever is out there, this is our best opportunity to find it’s story!

54. Now I want to speak as an experimentalist. I think this is not only the best opportunity but also this is a unique opportunity. If we wait too long, the window of opportunity may close and we will never hear the end of the story.