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The International Linear Collider (ILC) Project

The International Linear Collider (ILC) Project. Outline: Why? status of the SM e+e- physics at LEP/SLC Physics at the ILC How? some remarks about the design. Status of the Standard Model. We learned over the last ~50 years: The matter is composed of Quarks and Leptons

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The International Linear Collider (ILC) Project

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  1. The International Linear Collider (ILC) Project Outline: Why? status of the SM e+e- physics at LEP/SLC Physics at the ILC How? some remarks about the design Sabine Riemann DESY Summer Student Lectures

  2. Status of the Standard Model We learned over the last ~50 years: The matter is composed of Quarks and Leptons + anti-particles interacting via force carriers (Gauge Bosons) top-quark 1995 tau-neutrino 2000 missing: Higgs boson Sabine Riemann DESY Summer Student Lectures

  3. Forces: different strengths depending on energy at high energies: ‚democratic‘……..unification  situation immediately after creation of the Universe Sabine Riemann DESY Summer Student Lectures

  4. Standard Model •mathematical description of all interactions, involving weak, electromagnetic, strong forces, through closely related symmetry principles (gauge symmetries) • Local gauge symmetry  Invariance under local phase transformation QED – invariant under local gauge transformations of U(1) group; photon is gauge boson 1967/68 Glashow - Salam - Weinberg:gauge theory to unify el.magn. and weak forces Standard Model of electroweak interaction Sabine Riemann DESY Summer Student Lectures

  5. Problem : gauge invariance only possible formasslessgauge bosons (m=0, R–>∞  Phase transformation can be compensated through gauge trafo everywhere in space) Massive gauge bosons  Violation of gauge invariance Solution: Introduction of a scalar background field (Higgs-Feld)in a gauge invariant way Sabine Riemann DESY Summer Student Lectures

  6. The Higgs mechanism Introduce SU(2)xU(1) invariantHiggs potential (Mexican hat) with ground state complex doublet of weak iso-spin (simplest case = SM): Sabine Riemann DESY Summer Student Lectures

  7. The Higgs mechanism (cont’d) • is invariant under SU(2)L x U(1)Y transformations  3 degrees of freedom are ‘eaten’ by the Higgs field  massless (W1,2,3) become massive, W±,Z and g • Ground state only invariant under U(1)Y transformation: SU(2)L x U(1)Y  U(1)em SM: only the most economic way of a Higgs mechanism Many more possibilities, e. g. two doublets (minimal SUSY), triplets, ... Higgs mechanism requires the existence of at least onescalar, massive Higgs boson. Sabine Riemann DESY Summer Student Lectures

  8. Sabine Riemann DESY Summer Student Lectures

  9. How can we test the Standard Model ? Test of SM: precise measurements of SM parameters consistency checks Sabine Riemann DESY Summer Student Lectures

  10. Hadron Collider OR Lepton Collider ?? e+ e- p p proton = composite particle:unknown √s of partons,no polarization of partons,parasitic collisions proton = strongly interacting:huge SM backgrounds,highly selective trigger needed,radiation hard detectors needed e = pointlike particle:known and tunable √s of particles,polarization of particles possible,kinematic contraints can be used e = electroweak interactionslow SM backgrounds,no trigger needed,detector design driven by precision high energy↔ high precision Both approaches are needed for a better understanding! Sabine Riemann DESY Summer Student Lectures

  11. Sabine Riemann DESY Summer Student Lectures

  12. Lessons from LEP Sabine Riemann DESY Summer Student Lectures

  13. LEP: Large Electron Positron collider Sabine Riemann DESY Summer Student Lectures

  14. The nineties – precision physics at LEP and SLC Sabine Riemann DESY Summer Student Lectures

  15. Precision physics: Sabine Riemann DESY Summer Student Lectures

  16. 2 2 2 2 2 = + + g exchange gZ interference Z exchange Sabine Riemann DESY Summer Student Lectures

  17. Cross section at the Z resonance High statistics (17 106) • measure mZ • determine G • determine couplings Sabine Riemann DESY Summer Student Lectures

  18. Number of light neutrinos Sabine Riemann DESY Summer Student Lectures

  19. Born cross section is only approximation !!! Precise measurements  sensitive to top-quark and Higgs boson Sabine Riemann DESY Summer Student Lectures

  20. Sabine Riemann DESY Summer Student Lectures

  21. Sabine Riemann DESY Summer Student Lectures

  22. Cross section at the Z resonance High statistics • measure mZ • determine G • determine couplings •  indirect information • about mt and mH • from electroweak • corrections Sabine Riemann DESY Summer Student Lectures

  23. Top mass predicted at LEP BEFORE top discovery Precision measurements @ LEP/SLC Discovery @ Tevatron, 1994 Sabine Riemann DESY Summer Student Lectures

  24. The SM Higgs Mass Precision measurements Lower limit from direct measurements Sabine Riemann DESY Summer Student Lectures

  25. LEP 2 Higgs Search • reconstruct Z • mH = E – mZ • LEP2 kinematic limit: ~115GeV Sabine Riemann DESY Summer Student Lectures

  26. Candidate for e+e-  ZH  e+e-qq Sabine Riemann DESY Summer Student Lectures

  27. LEP 2: W pair production cross section Gauge-boson coupling  confirmation of SM gauge structure Sabine Riemann DESY Summer Student Lectures

  28. Status SM today SM tested at loop level SM describes measurements – so far no deviations obtained This plot is the result of ~30 years physics at hadron and lepton colliders! Präzision measurements are dominating! • ZHH „Particle Physics today is in an excellent yet curious state“(TESLA TDR) Sabine Riemann DESY Summer Student Lectures

  29. Why do we need the ILC? Sabine Riemann DESY Summer Student Lectures

  30. Physics at the ILC Comprehensive and high precision coverage of energy range from MZ to ~ 1 TeV • Higgs Mechanism • Supersymmetry • Strong Electroweak Symmetry Breaking • Precision Measurements at lower energies (GigaZ) Important Physics Topics cross sections few fb to few pb  e.g. O(10,000) HZ/yr Sabine Riemann DESY Summer Student Lectures

  31. Precision Measurements of the SM s(pb) Measurement of top-quark mass by threshold scan of cross section theoretical uncertainty dominates DM ~ 100 MeV Luminosity = 100 fb-1 ECM(GeV) GigaZ: Operation of TESLA at the Z resonance and WW threshold: 1 billion Z’s in a few months (~50xLEP) 2 • very high precision of theoretical predictions is needed! • DsinqW= 0.000013 (1/13xLEP1) DMW = 6MeV (1/3xLEP2) Sabine Riemann DESY Summer Student Lectures

  32. The Giga Z option •  high luminosity running at the Z-pole • Giga Z (109 Z/year) ≈ 1000 x “LEP” in 3 months • with e- and e+ polarisation ΔsinΘW = 0.000013 together with ΔMW = 7 MeV (threshold scan) and ΔMtop = 100 MeV Sabine Riemann DESY Summer Student Lectures

  33. The Higgs Profile • Mass (in SM mass determines the profile completely) • Total decay width • Coupling to Z and W: Mw~ g v, MZ ~ g v (g: gauge coupling, v: vacuum expectation value) • Coupling to fermions: mf = gf v • Higgs self-coupling, Higgs potential Aim: Establish the Higgs Mechanism as responsible for mass creation and electroweak symmetry breaking How to do that ? High precision measurements!  confirm the Standard Model OR  hints to new physics due to deviations from SM predictions Sabine Riemann DESY Summer Student Lectures

  34. Production of the Higgs Boson Higgs-Strahlung WW-Fusion NHiggs = s L Expect ~17 Higgs events per hour ECM=500 GeV, MH=120 GeV Higgs factory !! Sabine Riemann DESY Summer Student Lectures

  35. Higgs Mass and Higgs Coupling to the Z Select events: e+e-  ZH mit Z mm,ee Fit to the spectrum of recoil mass of both leptons  Peak position Peak height DsZH ~ 5-6% Dm ~ 100 MeV sZH ~ gZ2 model-independent determinatin of ZH coupling gZ DgZ ~ 2-3% Dm ~ 40 - 80 MeV can be reached if Higgs decay is fully reconstructed Sabine Riemann DESY Summer Student Lectures

  36. b b Higgs coupling to the W Boson WW fusion process: bb +missing energy (n n) Fit to the spectra of missing mass s~ gw2x BR(Hbb) determine BR(Hbb) in ZH process, then model-independent measurement of gw DgW ~ 3 - 13% Sabine Riemann DESY Summer Student Lectures

  37. Higgs Couplings to Fermions Higgs Mechanism  fermion masses mf ~ gf G(Hff)~ mf2 Test with determination of BR(Hff) from measurements of sZHxBR(Hff) decay rel. error -1 for 500 fb , mH=120 GeV BR(mm)~10-4: DBR(mm)/BR(mm) = 32 % for 1 ab-1 and E=800GeV Sabine Riemann DESY Summer Student Lectures

  38. Top Quark Yukawa Coupling Top Quark Yukawa Coupling = O(1) im SM» other fermions Surprise ?? Small cross section and „high mass“ in final state • high energy, ECM = 800 GeV  high luminosity, L = 1 ab-1 DgttH/gttH = 7 to 13 % For mH =120 to 200 GeV Sabine Riemann DESY Summer Student Lectures

  39. Determination of Quantum Numbers SM prediction: Spin = 0, CP = odd Spin J: “threshold scan” of cross section eeZHll X (model-independent) CP: From angular distributions of Z and f from Zff in eeZH (model-independent) -1 10 fb /point Sabine Riemann DESY Summer Student Lectures

  40. Higgs Self-Coupling Do we see the Higgs ? Is it ew symmetry breaking? Reconstruction of potential = Measurement of Triple-Higgs coupl. V(F)=m2|F|2 + l |F|4 m2<0, l>0 Vacuum expectation value n2 = - m2/l V(H) = l n2 H2 + l n H3 + ¼ l H4 mH2 = 2 l n2 Sabine Riemann DESY Summer Student Lectures

  41. Higgs Self-Coupling Sensitive to l Ds/s=13 %  Dl/l=23 % • tiny x-section: 0.15 fb • need high luminosity • Complex final state: • ZHZHHqq bb bb • Neural-net analysis: • S/Ö B = 6 Ds/s=13 % MH=120GeV, ECM= 500GeV, L=1ab-1 Sabine Riemann DESY Summer Student Lectures

  42. The Higgs Profile PDG Booklet 201x ? E. Gross Why this precision ? Test of Standard Model Discrimination between SM Higgs sector and extensions i.e. Minimal Supersymmetric Standard Model (MSSM) 10-2 MSSM:5 Higgs bosons: h,H,A,H+- Two vacuum expectation values: tanb = v1/v2 Ö(v12+v22) = 246 GeV Free parameters at Born level:tanb, MA Sabine Riemann DESY Summer Student Lectures

  43. No Higgs Boson found? Scattering of massiv gauge bosons Unitarity violation s ~ s divergent at ≥ (if interaction remains weak) Solution : new QCD-like strong interaction (i.e. Technicolor) Experimental consequences: Deviation from SM expectations in Triple-Gauge-Boson Coupl.(TGC) and Quartic-Gauge-Boson Coupl.(QGC) (or direct observation of new resonances: i.e. Techni-Hadrons) Sabine Riemann DESY Summer Student Lectures

  44. The Hierarchy Problem Why is electroweak scale « Planck scale ?? v = 246 GeV Higgs boson: large scale depending mass corrections 2 DMH2 = aL2 =aMPlanck • Possible solutions: • Supersymmetry • with MSUSY ~ O(TeV) • d extra spatial dimensions: MPl4+d = 1TeV • No Higgs boson: strong dynamical symmetry breaking Sabine Riemann DESY Summer Student Lectures

  45. Extra dimensions Completely alternative approach to solve hierarchy problem:“There is no hierarchy problem” Suppose the SM fields live in “normal” 3+1 dim. space Gravity lives in 4 + d dimensions d extra dimensions are curled to a small volume (radius R) Sabine Riemann DESY Summer Student Lectures

  46. Extra Spatial Diminsions Classical: GN=1/MPl2 ADD-Model: Gravitation only ‚exists‘ in the d new spatial dimensions (compactified) with radius R: r«R r»R Compare 4-dim and 4+d V(r): MPl2=8p Rd MDd+2 If MD = 1 TeV : for d = 2(3) one finds R = 1 mm(nm) Sabine Riemann DESY Summer Student Lectures

  47. Extra Spatial Dimensions Compactification  Kaluza-Klein towers Infinite number of gravitational states : withDM=1/R MD = 1 TeV : d = 2(4,6) DM = 0.5 MeV (20keV, 7MeV) In experiments: Sabine Riemann DESY Summer Student Lectures

  48. Direct Production of Gravitons Signatur: 1 Photon + missing energy 1 ab-1 @500 GeV + 800 GeV Discovery (5s) up to Measurement of x-section at 500 and 800 GeV allows determination of MDandd !! Sabine Riemann DESY Summer Student Lectures

  49. Exchange of Gravitons Interference of photon, Z exchange (spin=1) and graviton exchange (Spin=2)  modified distribution of scattering angle  Sensitivity: (95% CL) 5.6 TeV @ 500 GeV 8.0 TeV @ 800 GeV Distinction between spin1 and spin2 is possible ! Sabine Riemann DESY Summer Student Lectures

  50. Summary (physics) • fascinating physics potential could not shown completely in this lecture • Key word: Precision high luminosity  excellent detector  precise theoretical predictions • top physics at the threshold (E=350 GeV) • Higgs: mass, couplings, gauge structure • inconsistencies with SM ? • new physics: extra dimensions SUSY, strong ew symmetry breaking • synergy with LHC (constraints, additional information) Sabine Riemann DESY Summer Student Lectures

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