1. DESY Summer Program 2011 Gudrid Moortgat-Pick 1 Physics at e + e - Colliders Gudrid Moortgat-Pick Hamburg University, 17.8.2011 Introduction Achievements with LEP, SLC Physics beyond the Standard Model: supersymmetry Techniques at the high-energy e + e - collider ILC physics potential in view of LHC expectations Summary and some literature for further studies

2. DESY Summer Program 2011 Gudrid Moortgat-Pick 2 Few words before … You heard already a lot about –how e+e- colliders work –how they are limited –how the physics is detected –how we describe the physics theoretically –summary on physics issues I do not want to repeat the things, therefore I will focus on only a few physics topics (top, Higgs, SUSY, ED) and a few technical tools (threshold scans, continuums measurements, beam polarization) – Discussions: any time, please feel free to ask questions….

3. DESY Summer Program 2011 Gudrid Moortgat-Pick 3 Introduction Characteristics of pp collider: composite particles collide E(CM) < 2 E(beam) strong interaction in initial state superposition with spectator jets LHC: √s = 7 14TeV, used ŝ = x 1 x 2 s few TeV small fraction of events analyzed multiple triggers `no' polarization applicable Large potential for direct discoveries and of the e +e-(γe, γ γ) collider: pointlike particles collide E(CM) = 2 E(beam) well defined initial state clean final state ILC: √s = 90 GeV -- 1 TeV, tunable CLIC: √s=3 TeV most events in detector analyzed no triggers required polarized initial beams possible Large potential for direct dis- coveries and via high precision

4. DESY Summer Program 2011 Gudrid Moortgat-Pick 4 Discoveries at e+e- colliders Some examples of direct discoveries at e+e- colliders: J/ Ѱ at SPEAR at SLAC (1974) Gluons at PETRA at DESY (1979) famous ‘3 jet events’

5. DESY Summer Program 2011 Gudrid Moortgat-Pick 5 The unique advantage of e+e- Their clean signatures allow precision measurements Sensitive to the theory at quantum level (i.e. contributions of virtual particles, ‘higher orders’)! Such measurements allow predictions for effects of still undiscovered particles, but whose properties are defined by theory.

6. DESY Summer Program 2011 Gudrid Moortgat-Pick 6 Prediction of the top quark mass Predicted discovery of the top quark at the Tevatron 1995! Predicted discoveries: e+, n, π, q, g,W, Z, c, b, t Future examples: Higgs, SUSY ??? -- see later

7. DESY Summer Program 2011 Gudrid Moortgat-Pick 7 Some LEP data Circumference 27 km √s 91.2 GeV (LEP1) to 209 GeV(LEP2) Accelerating Gradient Up to 7MV/m (Superconducting cavities) Number of Bunches 4 × 4 Current per Bunch ≈ 750 μA Luminosity at LEP1 24 × 10 30 cm −2 s −1 (≈ 1 Z 0 /s) Luminosity at LEP2 50 × 10 30 cm −2 s −1 (≈ 3 W + W − /h) Interaction regions 4 (ALEPH,DELPHI,L3,OPAL) Energy calibration < 1MeV (at Z 0 )

8. DESY Summer Program 2011 Gudrid Moortgat-Pick 8 LEP data 1990 – ≈ 91 GeV 1995 5 Million Z 0 /exp. 1995 Test phase for LEP2 130GeV 1996 161 − 172 GeV WW-Threshold 1997 183 − 209 GeV 2000 10 000 WW-pairs/exp. Searches for new physics 0 (?) Higgs bosons LEP was shut down and dismantled to make room for LHC in Nov. 2000 Integrated Luminosities LEP measured sin 2 θ eff = from A FB (had)

9. SLC data and features Stanford Linear Collider –e + e - at √s=91.26 GeV: the ‘Z’ pole –Luminosity ~ 3 x 10 30 cm -2 s -1 –Special feature:highly polarized e - -beam ! P(e-)~78% –Best single measurement of weak mixing angle: sin 2 θ eff = 0.23098 ± 0.00026 from A LR (l) Higher precision although lower luminosity!!! More examples fort use of polarization, see later … DESY Summer Program 2011 Gudrid Moortgat-Pick 9

10. 10 Back to LEP1: the Basic Process Z 0 lineshape: Z 0 mass, Z 0 /γ-interference Number of neutrinos, etc. Precision tests of the QFD: forward-backward asymmetries Precision tests of QCD: Confirmation of SU(3) Together with m W : Prediction of the top quark mass Many other precision tests of the SM Very successful: more than 2400 publications from 4 collaborations !

11. DESY Summer Program 2011 Gudrid Moortgat-Pick 11 First Z - event e+e- -> Z -> q q (13.8.89 !) –Tracking chambers not yet fully operational, therefore only ECAL

12. DESY Summer Program 2011 Gudrid Moortgat-Pick 12 Total cross section Z 0 gives a dramatic resonance cross section well described (at quantum level, not only at tree level!)

13. DESY Summer Program 2011 Gudrid Moortgat-Pick13 Z 0 Mass Measurement Very important input to SM fits ! Uncertainty is only ∆m Z ~2.1MeV Important to understand systematics of the beam energy measurement!

14. DESY Summer Program 2011 Gudrid Moortgat-Pick 14 Systematics: Beam Energy Measurement Uncertainty is only 1MeV ! Further systematics have been: water level, tides, TGV Remark: polarization not used for physics, but for calibration!

15. DESY Summer Program 2011 Gudrid Moortgat-Pick 15 Z 0 branching ratios: neutrinos –measure ‘invisible’ events ! (also important for SUSY, see later)

16. DESY Summer Program 2011 Gudrid Moortgat-Pick 16 Counting neutrinos via photons! Using radiative neutrino production: –leads to signal only in ECAL

17. DESY Summer Program 2011 Gudrid Moortgat-Pick 17 Fitting the cross section: Fit prefers 3 families but rather large error Some theory assumptions but better than nothing…

18. DESY Summer Program 2011 Gudrid Moortgat-Pick18 Other method for counting neutrinos Measuring the total width of the Z (‘life-time’)

19. DESY Summer Program 2011 Gudrid Moortgat-Pick 19 Exploiting further observables: angular distributions! linear dependence on scattering angle cosθ: –n

20. DESY Summer Program 2011 Gudrid Moortgat-Pick 20 Measuring Z 0 couplings Vector- and axial-vector couplings: –g Vl =T 3l -2 e sin 2 θ W –g Al =T 3l T 3l =weak isospin =-1/2 for e

21. DESY Summer Program 2011 Gudrid Moortgat-Pick21 Measuring the ew mixing angle Measuring the AFB can be interpreted as measuring sin 2 θ W Result (only LEP): sin 2 θ W =0.23221±0.00029 –Result improved by inclusion of other experiments, e.g. SLD (see later) –Discrepancy between A FB and A LR -> impact on Higgs tests !

22. DESY Summer Program 2011 Gudrid Moortgat-Pick 22 Top mass prediction

23. DESY Summer Program 2011 Gudrid Moortgat-Pick 23 So far we have done … Discussion of LEP1 results, only as an example Because of time: rarely mentioned details from other e + e - experiments –SLD: very important also for sin 2 θ W (used polarized beams, see later) –LEP2: but also very rich program, as e.g. precision W mass measurement, searches for the Higgs boson, but also for new physics But why do we need physics beyond the SM and what are the experimental challenges?

24. Open questions …and possible answers LHC2FC@CERN 02/09 Gudrid Moortgat-Pick 24 Shortcomings of the Standard Model Unification of all interactions? ILC,CLIC Hierarchy problem? LHC,ILC Establish electroweak symmetry breaking ILC,CLIC Embedding of gravity cosmo,LHC/ILC Neutrino mixing and masses v-, cosmo-exp. Baryon asymmetry in Universe? v-, cosmo, LHC, ILC Dark matter v-, cosmo, LHC, ILC Why TeV scale? Protect hierarchy between m weak and m planck Dark matter consistent with sub-TeV scale WIMPs

25. DESY Summer Program 2011 Gudrid Moortgat-Pick 25 Shortcomings of the Standard Model doesn't contain gravity doesn't explain neutrino masses doesn't have candidate for dark matter 23% of universe is cold dark matter! no unification of gauge couplings possible further problem: `hierachy problem' Higgs mass unstable w.r.t. large quantum corrections:

26. DESY Summer Program 2011 Gudrid Moortgat-Pick 26 The Hierarchy Problem

27. DESY Summer Program 2011 Gudrid Moortgat-Pick 27 Hierarchy Problem 2

28. DESY Summer Program 2011 Gudrid Moortgat-Pick 28 Hierarchy Problem 3

29. DESY Summer Program 2011 Gudrid Moortgat-Pick 29 Hierarchy Problem 4

30. DESY Summer Program 2011 Gudrid Moortgat-Pick 30 Supersymmetry – intro 1

31. DESY Summer Program 2011 Gudrid Moortgat-Pick 31 Supersymmetry – intro 2

32. DESY Summer Program 2011 Gudrid Moortgat-Pick 32 Supersymmetry – intro 3

33. DESY Summer Program 2011 Gudrid Moortgat-Pick 33 Supersymmetry – intro 4

34. DESY Summer Program 2011 Gudrid Moortgat-Pick 34 Supersymmetry – intro 5

35. DESY Summer Program 2011 Gudrid Moortgat-Pick 35 Supersymmetry – intro 6

36. DESY Summer Program 2011 Gudrid Moortgat-Pick36 Soft SUSY Breaking

37. DESY Summer Program 2011 Gudrid Moortgat-Pick 37 Free parameters in the MSSM

38. Unconstrained MSSM DESY Summer Program 2011 Gudrid Moortgat-Pick38 No particular SUSY breaking mechanism is assumed –105 parameters, but no quadratic divergencies Constrained models (4 to 5 parameters only): assumptions New quantum number: R-parity=(-1) 3B+L+2S (SM=+1, SUSY=-1) – If conserved: lightest particle is stable ….’dark matter candidate’ – Most general and renormalizable superpotential

39. DESY Summer Program 2011 Gudrid Moortgat-Pick 39 Particle content in the MSSM

40. DESY Summer Program 2011 Gudrid Moortgat-Pick 40 Properties of SUSY - Unification

41. DESY Summer Program 2011 Gudrid Moortgat-Pick 41 Prospects of SUSY at future colliders

42. Goals and features at a LC Direct production up to kinematical limit –tunable energy: threshold scans ! Extremely clean signatures –polarized beams available –impressive potential also for indirect searches via precision Unravelling the structure of NP –precise determination of underlying parameters –model distinction through model independent searches High precision measurements –test of the Standard Model (SM) with unprecedented precision –even smallest hints of NP could be observed Discovery of new phenomena via high energy and high precision! DESY Summer Program 2011 Gudrid Moortgat-Pick 42

43. DESY Summer Program 2011 Gudrid Moortgat-Pick 43 Beam polarization at colliders

44. DESY Summer Program 2011 Gudrid Moortgat-Pick 44 e+ polarization is an absolute novelty! Expected P(e+) ~ 60%

45. DESY Summer Program 2011 Gudrid Moortgat-Pick 45 Electron polarization

46. DESY Summer Program 2011 Gudrid Moortgat-Pick 46 Polarized positrons 150

47. DESY Summer Program 2011 Gudrid Moortgat-Pick 47 How to describe the spin?

48. DESY Summer Program 2011 Gudrid Moortgat-Pick 48 Remarks about couplings structure Definition: Helicity λ=s * p/|p| ‘projection of spin’ Chirality = handedness is equal to helicity only of m=0!

49. DESY Summer Program 2011 Gudrid Moortgat-Pick 49 General remarks, cont.

50. DESY Summer Program 2011 Gudrid Moortgat-Pick 50 Start: Statistical arguments for P(e+) Polarized cross sections can be subdivided in: σ RR, σ LL, σ RL, σ LR are contributions with fully polarized L, R beams. In case of a vector particle only (LR) and (RL) configurations contribute:

51. DESY Summer Program 2011 Gudrid Moortgat-Pick 51 Statistics 2 Polarized cross section reads: With effective luminosity

52. DESY Summer Program 2011 Gudrid Moortgat-Pick 52 Statistics 3 Effective polarization:

53. DESY Summer Program 2011 Gudrid Moortgat-Pick 53 Statistics 4

54. DESY Summer Program 2011 Gudrid Moortgat-Pick 54 Statistics 5 How are P eff and A LR related? That means: With pure error propagation (and errors uncorrelated), one obtains: With

55. DESY Summer Program 2011 Gudrid Moortgat-Pick 55 Statistics 6

56. DESY Summer Program 2011 Gudrid Moortgat-Pick 56 Background suppression

57. DESY Summer Program 2011 Gudrid Moortgat-Pick 57 Back to the ILC physics case … But since the ILC can not start before 2020, all physics issues have to be seen in view of expected LHC results In the following we discuss several physics topics, starting at 500 GeV, 1TeV, multi-TeV Applying the mentioned tools, threshold scans, beam polarization, precision measurements But only a personal selection of examples ……

58. DESY Summer Program 2011 Gudrid Moortgat-Pick 58 Physics up to sqrt(s)=500 GeV: top m top = 173.3 +- 1.1 GeV

59. DESY Summer Program 2011 Gudrid Moortgat-Pick 59 Top mass 3 We expect at the LC:

60. Importance of ‘top’ mass DESY Summer Program 2011 Gudrid Moortgat-Pick 60

61. DESY Summer Program 2011 Gudrid Moortgat-Pick 61 Electroweak symmetry breaking / Higgs M h <185 GeV Currently LHC: maybe m H ~120-140 GeV ???

62. DESY Summer Program 2011 Gudrid Moortgat-Pick 62 Determination of Higgs properties LHC input for optimal choices of running scenarios ! Higgs spin

63. DESY Summer Program 2011 Gudrid Moortgat-Pick 63 Higgs mass at ILC

64. DESY Summer Program 2011 Gudrid Moortgat-Pick 64 Higgs mass, 2 Use Higgsstrahlung: due to well-known initial state and well-observed Z-decays –Derive Higgs mass independently from decay –Only possible at a LC!

65. DESY Summer Program 2011 Gudrid Moortgat-Pick 65 Higgs properties

66. SUSY expectations DESY Summer Program 2011 Gudrid Moortgat-Pick 66

67. Status LHC results First LHC results based on L=35pb-1: –Exclusion bounds in mSUGRA for couloured spectrum Remember talks from EPS conference 67 From: pp -> 2 jets +MTE mSUGRA scenario coloured g,q > 500 GeV Interpretation in mSUGRA electroweak sector: m χ 0 2 ~200 GeV still rather light… CMS, arXiv: 1101.1628 DESY Summer Program 2011 Gudrid Moortgat-Pick ~~ ~

68. Status LHC results, cont. ATLAS-result: 68 From: pp -> 2 jets +MTE mSUGRA scenario q,g > 700-800 GeV Interpretation in mSUGRA electroweak sector: m χ 0 2 ~300 GeV SPS1a `excluded’ many particles out of kinematical range for √s=500 GeV but remember, that’s just in mSUGRA! DESY Summer Program 2011 Gudrid Moortgat-Pick ~~ ~ News see talk by G. Weiglein next week….

69. But – is mSUGRA the full truth? Remember: we have 105 new SUSY parameters (instead of only 4) … –`everything’ is possible –but the full MSSM is a more long-term goal –No ‘real’ fitting option Relation between particles depends crucially on the SUSY breaking scenario –Study different breaking scenarios with also only a few parameters –Get a feeling whether we walk on the right interpretation path…. 69DESY Summer Program 2011 Gudrid Moortgat-Pick

70. New SUSY breaking developments For instance, hybrid models: flavourful anomaly-gravity mediation 70 C. Gross, G. Hiller, arXiv: 1101.5352 heavy coloured sector ‘light’ electroweak sector Further advantages: no tachions due to flavour dependence heavy gravitino: benefitial for cosmology Very interesting model DESY Summer Program 2011 Gudrid Moortgat-Pick

71. Is this the only solution? Or take AMSB scenarios: 71 Similar feature: heavy coloured but also light uncoloured spectrum Technical challenge: Mass degeneration Only few pheno LC studies performed in the past Uli Martyn, Nabil Ghodbane, hep-ph/0201233 DESY Summer Program 2011 Gudrid Moortgat-Pick

72. Or remember good ‘old’ examples Have a look on GMSB scenarios (`SPS7’): 72 Again: a heavy couloured spectrum is natural in this scenario but also a rather light electroweak sector….. But: technical challenges many т’s, etc. still many detailed ILC studies missing! …… Uli Martyn, Nabil Ghodbane, hep-ph/0201233 DESY Summer Program 2011 Gudrid Moortgat-Pick

73. 73 Back to work: discovery of SUSY

74. DESY Summer Program 2011 Gudrid Moortgat-Pick 74 SUSY mass determinations at the LHC

75. DESY Summer Program 2011 Gudrid Moortgat-Pick 75 SUSY mass measurement im continuum

76. DESY Summer Program 2011 Gudrid Moortgat-Pick 76 Mass measurement of the LSP mass

77. DESY Summer Program 2011 Gudrid Moortgat-Pick 77 Test off spin quantum number at ILC Clean signatures, known initial state, tunable energy :

78. DESY Summer Program 2011 Gudrid Moortgat-Pick 78 One more SUSY Test at the ILC

79. DESY Summer Program 2011 Gudrid Moortgat-Pick 79 Chiral quantum numbers, 2

80. DESY Summer Program 2011 Gudrid Moortgat-Pick 80 LHC/ILC interplay

81. DESY Summer Program 2011 Gudrid Moortgat-Pick 81 Indirect searches: extra dimensions

82. DESY Summer Program 2011 Gudrid Moortgat-Pick 82 Extra dimensions

83. DESY Summer Program 2011 Gudrid Moortgat-Pick 83 EW precision measurements GigaZ option at the ILC: –high-lumi running on Z-pole/WW –10 9 Z in 50-100 days of running –Needs machine changes (bypass in the current outline) High precision needs polarized beams Provides measurement of sin 2 θ W with unprecedented precision!

84. DESY Summer Program 2011 Gudrid Moortgat-Pick 84 Electroweak precision test 2

85. Electroweak precision observables EWPO: α, G F, M Z, M W, Г l, sin 2 θ eff, g μ -2, … – One example: precise measurement of M W = 80.399±0.023 GeV accuracy of 0.3‰ leading to sensitivity to 1- and 2-loop quantum effects … Previous experimental results at the Z-pole: LEP: very precise measurement of M Z, Г Z, A FB (l), A FB (b,c),… SLD: A LR (e), A LR (μ), … Of particular interest: sin 2 θ eff = 1-M W 2 /M 2 Z + loop effects Determined from A FB, A LR High sensitivity to effects of new physics ! 85 DESY Summer Program 2011 Gudrid Moortgat-Pick

86. Physics gain of polarized beam(s) Past experience: – excellent e- polarization ~78% at SLC: – led to best single measurement of sin 2 θ=0.23098±0.00026 on basis of L~10 30 cm -2 s -1 Compare with results from unpolarized beams at LEP: – sin 2 θ=0.23221±0.00029 but with L~10 31 cm -2 s -1 polarization can even compensate order of magnitude in luminosity for specific observables ! 86 DESY Summer Program 2011 Gudrid Moortgat-Pick

87. Current experimental situation 87 LEP: sin 2 θ eff (A FB b )= 0.23221±0.00029 SLC: sin 2 θ eff (A LR )= 0.23098±0.00026 World average: sin 2 θ eff = 0.23153±0.00016 Discrepancy between the two most precise measurements Central value has large impact on physics predictions! DESY Summer Program 2011 Gudrid Moortgat-Pick

88. Theory vs. experiment: M W – world av. of sin 2 θ eff 88 → Consistent with Standard Model and MSSM (unconstrained) Heinemeyer, Weiglein DESY Summer Program 2011 Gudrid Moortgat-Pick

89. M W - A LR (SLD)-value sin 2 θ eff 89 → large deviation from the Standard Model Heinemeyer, Weiglein DESY Summer Program 2011 Gudrid Moortgat-Pick

90. M W - A FB (LEP )-value sin 2 θ eff 90 → large deviation from both, the Standard Model and the MSSM Precise sin 2 θ eff -measurement has the potential to rule out both models ! Heinemeyer, Weiglein DESY Summer Program 2011 Gudrid Moortgat-Pick

91. sin 2 θ eff at the Z-factory Measure both A FB and A LR in same experiment ! with improved precision w.r.t. LEP and SLC: A LR : large gain from polarization of both beams and higher luminosity A FB : gain from higher luminosity, better b-tagging, etc. resolve unclear situation: New physics affecting A FB (b) and A LR (l) in different ways? Resolution of experimental discrepancy: reliable central value+ improved precision large impact on interpretation of LHC results! 91 DESY Summer Program 2011 Gudrid Moortgat-Pick

92. Which precision should one aim for NOW? Theoretical uncertainties: Δsin2θ eff ho ~5x10 -5 (currently) Uncertainties from input parameters: Δm Z, Δα had, m top Δm Z =2.1 MeV: Δsin 2 θ eff para ~1.4x10 -5 Δα had ~10 ( 5 future) x 10 -5 : Δsin 2 θ eff para ~3.6 (1.8 future )x10 -5 Δm top ~1 GeV (LHC): Δsin 2 θ eff para ~3x10 -5 Δm top ~0.1 GeV (ILC): Δsin 2 θ eff para ~0.3x10 -5 If Δsin 2 θ eff ~ 3x10 -5 achievable: already big physics impact 92 Davier, ’10: DESY Summer Program 2011 Gudrid Moortgat-Pick

93. Possible result of a Z-factory : Δ sin 2 θ eff ~ 3x10 -5 93 would unambiguously rule out SM+MSSM ! Higher precision mandatory to fix central value! What’s the benefit of higher precision? Heinemeyer, Weiglein DESY Summer Program 2011 Gudrid Moortgat-Pick

94. 94 Blondel scheme for GigaZ @ILC Would be ultimate precision…..

95. DESY Summer Program 2011 Gudrid Moortgat-Pick 95 SUSY Constraints from GigaZ

96. DESY Summer Program 2011 Gudrid Moortgat-Pick 96 Only Higgs @LHC No hints for SUSY Deviations in sin 2 θ eff – hints for SUSY Powerful test! – Do not miss it Help in worst case scenarios ?

97. DESY Summer Program 2011 Gudrid Moortgat-Pick97 Physics up to 1 TeV Direct search for extra dimensions

98. DESY Summer Program 2011 Gudrid Moortgat-Pick 98 Direct search for extra dimensions

99. DESY Summer Program 2011 Gudrid Moortgat-Pick 99 Multi-TeV option at CLIC - Higgs

100. DESY Summer Program 2011 Gudrid Moortgat-Pick100 Summary e+e- physics has been the core of high precision physics over the last decade Results from LEP, SLD, B-factories provide tests of the SM at quantum level! We expect a fascinating future in the next years: LHC will shed first light on the mysteries of EW symmetry breacking Rich program and high physics potential of the ILC will unravel the new physics and enter a new precision frontier! Stay tuned for the LHC and (I)LC! ( Klaus Desch @CERN 02/09)

101. DESY Summer Program 2011 Gudrid Moortgat-Pick 101 Some literature ILC physics: TESLA TDR, physics part hep-ph/0106315 ILC RDR, arXiv:0712.1950 LHC/ILC interplay: G. Weiglein, Phys. Rept. 426, 47 (2006), hep-ph/0410364 Supersymmetry: introduction M. Drees, hep-ph/9611409, S. Martin, hep-ph/9709356 Polarization+Spin: GMP, POWER report, Phys. Rept. 460,131 (2008), hep-ph/0507011 webpage: www.ippp.dur.ac.uk/LCsources