1. Review of the Open Questions and the Potential for Discoveries ICFA Seminar Taegu, September 2005 John Ellis, TH Division, PH Department, CERN

2. Open Questions beyond the Standard Model What is the origin of particle masses? due to a Higgs boson? + other physics? solution at energy < 1 TeV (1000 GeV) Why so many types of matter particles? matter-antimatter difference? Unification of the fundamental forces? at very high energy ~ 10 16 GeV? probe directly via neutrino physics, indirectly via masses, couplings Quantum theory of gravity? (super)string theory: extra space-time dimensions?

3. At what Energy is the New Physics? A lot accessible to the LHC, ILC Some accessible only indirectly Dark matter Origin of mass

4. The State of the Higgs: Summer 2005 Direct search limit: m H > 114 GeV Electroweak fit sensitive to m t Currently m t = 172.7 ± 2.9 GeV (previously m t = 178 → 174.3) Best-fit value: m H = 91 +45 –32 GeV 95% confidence-level upper limit: m H < 186 GeV, or 219 GeV including direct limit

5. Indications on the Higgs Mass Sample observable: W mass @ LEP & Tevatron Combined information on Higgs mass Summer 2005

6. Theorists getting Cold Feet Composite Higgs model? conflicts with precision electroweak data Interpretation of EW data? consistency of measurements? Discard some? Higgs + higher-dimensional operators? corridors to higher Higgs masses? Little Higgs models? extra `Top’, gauge bosons, `Higgses’ Higgsless models? strong WW scattering, extra D?

7. Elementary Higgs or Composite? Higgs field: ≠ 0 Quantum loop problems Fermion-antifermion condensate Just like QCD, BCS superconductivity Top-antitop condensate? needed m t > 200 GeV New technicolour force? inconsistent with precision electroweak data? Cut-off Λ ~ 1 TeV with Supersymmetry? Cutoff Λ = 10 TeV

8. Heretical Interpretation of EW Data Do all the data tell the same story? e.g., A L vs A H What attitude towards LEP, NuTeV? What most of us think

9. Higgs + Higher-Order Operators Precision EW data suggest they are small: why? But conspiracies are possible: m H could be large, even if believe EW data …? Do not discard possibility of heavy Higgs Corridor to heavy Higgs?

10. ‘Little Higgs’ Models Loop cancellation mechanisms SupersymmetryLittle Higgs How to cancel loops?

11. Higgsless Models? Four-dimensional versions: Strong WW scattering @ TeV, incompatible with precision data? Break EW symmetry by boundary conditions in extra dimension: delay strong WW scattering to ~ 10 TeV? Kaluza-Klein modes: m KK > 300 GeV? compatibility with precision data? Lightest KK mode @ 300 GeV, strong WW @ 6-7 TeV

12. Higgs Discovery @ Tevatron?

13. Higgs Detection at the LHC m H > 114.4 GeV here discovery easier with H  4 eptons The Higgs may be found quite quickly … … in several different channels Higgs detection easier if heavier!

14. Tasks for the TeV ILC Measure m t to <  100 MeV If there is a light Higgs of any kind, pin it down: Does it have standard model couplings? What is its precise mass? If there are extra light particles: Measure mass and properties If LHC sees nothing new below ~ 500 GeV: Look for indirect signatures

15. Precision Higgs Physics @ ILC Higgs peak recoiling against Z →μμ Accuracy in Higgs couplings vs Standard Model, 2-Higgs doublets

16. Advantages of Higher Energy LC Larger cross section @ 3 TeV can measure rare decay modes H  bb Δg/g = 4%Δg/g = 2% m H = 120 GeVm H = 180 GeV

17. Loop Corrections to Higgs Mass 2 Consider generic fermion and boson loops: Each is quadratically divergent: ∫ Λ d 4 k/k 2 Leading divergence cancelled if Supersymmetry! 2 ∙2

18. Other Reasons to like Susy It enables the gauge couplings to unify Approved by Fabiola Gianotti It predicts m H < 150 GeV

19. Astronomers say that most of the matter in the Universe is invisible Dark Matter Lightest Supersymmetric particles ? We shall look for them with the LHC

20. Possible Nature of Supersymmetric Relic from Big Bang No strong or electromagnetic interactions Otherwise would bind to matter Detectable as anomalous heavy nucleus Possible weakly-interacting scandidates Sneutrino (Excluded by LEP, direct searches) Lightest neutralino χ (partner of Z, H, γ) Gravitino (nightmare for astrophysical detection)

21. Current Constraints on CMSSM WMAP constraint on relic density Excluded because stau LSP Excluded by b  s gamma Excluded (?) by latest g - 2 Assuming the lightest sparticle is a neutralino JE + Olive + Santoso + Spanos

22. Supersymmetry Searches at LHC `Typical’ supersymmetric Event at the LHC LHC reach in supersymmetric parameter space Can cover most possibilities for astrophysical dark matter

23. Studies of Supersymmetric Parameter Space Specific benchmark Points along WMAP lines Lines in susy space allowed by accelerators, WMAP data Sparticle detectability Along one WMAP line Calculation of relic density at a benchmark point Battaglia, De Roeck, Gianotti, JE, Olive, Pape

24. Sparticles at LC along WMAP Line Complementary to LHC: weakly-interacting sparticles Battaglia, De Roeck, Gianotti, JE, Olive, Pape

25. Examples of Sparticle Measurements Spectrum edges @ LHC Threshold excitation @ LC Spectra @ LC

26. Added Value of LC Measurements Determination of CMSSM parameters

27. Tests of Unification Ideas For gauge couplings For sparticle masses

28. Sparticles may not be very light Full Model samples Detectable @ LHC Provide Dark Matter Detectable Directly Lightest visible sparticle → ← Second lightest visible sparticle CLIC ILC JE + Olive + Santoso + Spanos

29. Sparticle Visibility at Higher E 3 TeV5 TeV See ‘all’ sparticles: measure heavier ones better than LHC CMSSM

30. What if Gravitino is Supersymmetric Relic? NLSP = next-to-lightest sparticle has very long lifetime due to gravitational decay, e.g.: Could be hours, days, weeks, months or years! Generic possibilities for NLSP: lightest neutralino χ lightest slepton, probably lighter stau

31. Minimal Supergravity Model (mSUGRA) Excluded by b  s γ LEP constraints On m h, chargino Neutralino LSP region stau LSP (excluded) Gravitino LSP region: Stau NLSP JE + Olive + Santoso + Spanos More constrained than CMSSM: m 3/2 = m 0, B λ = A λ – 1

32. Slepton Trapping at the LHC? If stau next-to-lightest sparticle (NLSP) may be metastable may be stopped in detector/water tank Feng + Smith Hamaguchi + Kuno + Nakaya + Nojiri Kinematics Trapping rate

33. All Sparticles → Stau NLSPs Triggers include staus Staus come with many jets & leptons with p T hundreds of GeV, produced centrally De Roeck, JE, Gianotti, Moortgat, Olive + Pape

34. Stau Mass Measurements by Time-of-Flight Event-by-event accuracy < 10% < 1% with full sample De Roeck, JE, Gianotti, Moortgat, Olive + Pape

35. Stau Momentum Spectra βγ typically peaked ~ 2 Staus with βγ < 1 leave central tracker after next beam crossing Staus with βγ < ¼ trapped inside calorimeter Staus with βγ < ½ stopped within 10m Can they be dug out? De Roeck, JE, Gianotti, Moortgat, Olive + Pape

36. Extract Cores from Surrounding Rock? Use muon system to locate impact point on cavern wall with uncertainty < 1cm Fix impact angle with accuracy 10 -3 Bore into cavern wall and remove core of size 1cm × 1cm × 10m = 10 -3 m 3 ~ 100 times/year Can this be done before staus decay? Caveat radioactivity induced by collisions! 2-day technical stop ~ 1/month Not possible if lifetime ~10 4 s, possible if ~10 6 s? De Roeck, JE, Gianotti, Moortgat, Olive + Pape Little room for water tanks in LHC caverns, mainly in forward directions where few staus

37. Open Questions beyond the Standard Model What is the origin of particle masses? due to a Higgs boson? + other physics? solution at energy < 1 TeV (1000 GeV) Why so many types of matter particles? matter-antimatter difference? Unification of the fundamental forces? at very high energy ~ 10 16 GeV? probe directly via neutrino physics, indirectly via masses, couplings Quantum theory of gravity? (super)string theory: extra space-time dimensions?

38. Super B Factory Physics Search for deviations from CKM CP violation Search for rare decays that may deviate from the Standard Model

39. Neutrino Mixing Diagonalize neutrino mass matrix in flavour space: where Two ‘observable’ Majorana phases as well as Maki-Nakagawa-Sakata (MNS) mixing matrix: MNS matrix has 3 real angles and 1 phase: Even more parameters in minimal seesaw model!

40. Chasing the Third Mixing Angle

41. Chasing the CP-violating Phase

42. Open Questions beyond the Standard Model What is the origin of particle masses? due to a Higgs boson? + other physics? solution at energy < 1 TeV (1000 GeV) Why so many types of matter particles? matter-antimatter difference? Unification of the fundamental forces? at very high energy ~ 10 16 GeV? probe directly via neutrino physics, indirectly via masses, couplings Quantum theory of gravity? (super)string theory: extra space-time dimensions?

43. String Theory Candidate theory of quantum gravity Point-like particles → extended objects Simplest possibility: lengths of string Open and/or closed Quantum consistency fixes # dimensions: Bosonic string: 26, superstring: 10 Requires extra dimensions How large are they? scale ~ 1/m P ?

44. How large could Extra Dimensions be? 1/TeV? could break supersymmetry, electroweak micron? can rewrite hierarchy problem Infinite? warped compactifications Look for black holes, Kaluza-Klein excitations @ colliders?

45. And if gravity becomes strong at the TeV scale … Black Hole Production at LHC? Multiple jets, leptons from Hawking radiation

46. Excitations in Models with Universal Extra Dimensions Spectra more degenerate than Susy - additional higher-level states Can be distinguished via mass, angular distributions

47. Kaluza-Klein Gravitons in e + e - Collisions Spectrum of excitations in Randall-Sundrum model Angular distribution in e + e - →μ + μ -

48. Summary There are good prospects for new physics discoveries with upcoming colliders Reasons to expect new physics @ TeV Higgs, supersymmetry, extra dimensions (?) Distinctive experimental signatures The LHC @ CERN will open new energy range Linear e+e- colliders could explore in more detail LHC will tell us the optimal energy