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Physics at a future Linear Collider

Physics at a future Linear Collider. ‘Big’ HEP questions LC technical requirements LC physics in view of LHC results Techniques at the high-energy e + e - collider Summary and some literature for further studies. Gudrid Moortgat-Pick Hamburg University, 20.8.2010.

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Physics at a future Linear Collider

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  1. Physics at a future Linear Collider • ‘Big’ HEP questions • LC technical requirements • LC physics in view of LHC results • Techniques at the high-energy e+e- collider • Summary and some literature for further studies Gudrid Moortgat-Pick Hamburg University, 20.8.2010 Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  2. Sceptical thoughts before…. • Many options and ideas for experiments • Most are expensive, some ‘rather’ cheap • Should cost be a criteria? Or diversity of the physics programme? • Priority lists are needed • Many lists exist (CERN strategy group, P5, UK roadmaps, German roadmaps…) • But big experiments require long term planning • To which extent are physics needs in advance predictable? Particle scales? Physics Models? … • Can we really weight today all options? • ILC, SLHC, LHeC, CLIC, ν-fact, DLHC, μ-collider,…. Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  3. (My ) Pragmatic approach • Physics: what are the ‘big’ questions? • Define steps ... ‘physics milestones’ • Identify which models tic which question • Common feature requirements: measure masses, couplings, spin, quantum numbers … ‘verify at quantum level’ • Machine: next physics milestone achievable? • Technical requirements for a LC have been defined • Synergy with other experiments • Some degree of flexibility required: ‘the unexpected’ Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  4. ‘Big’ questions …and possible answers • Shortcomings of the Standard Model • Establish electroweak symmetry breaking LC • Hierarchy problem? • Unification of all interactions? • Embedding of gravity • Baryon asymmetry in Universe? • Dark matter • Neutrino mixing and masses • Why TeV scale? • Protect hierarchy between mweak and mplanck • Dark matter consistent with sub-TeV scale WIMPs Higgs mass with respect to large quantum corrections: Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  5. ‘Big’ questions …and possible answers • Shortcomings of the Standard Model • Establish electroweak symmetry breaking LC • Hierarchy problem? LHC, LC • Unification of all interactions? LC • Embedding of gravity cosmo,LHC, LC • Baryon asymmetry in Universe? v-, cosmo, LHC, LC • Dark matterv-, cosmo, LHC, LC • Neutrino mixing and masses v-, cosmo-exp. • Why TeV scale? • Protect hierarchy between mweak and mplanck • Dark matter consistent with sub-TeV scale WIMPs Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  6. ‘Big’ questions …and possible answers • Shortcomings of the Standard Model • Establish electroweak symmetry breaking LC • Hierarchy problem? LHC, LC • Unification of all interactions? LC • Embedding of gravity cosmo,LHC, LC • Baryon asymmetry in Universe? v-, cosmo, LHC, LC • Dark matterv-, cosmo, LHC, LC • Neutrino mixing and masses v-, cosmo-exp. • Why TeV scale? • Protect hierarchy between mweak and mplanck • Dark matter consistent with sub-TeV scale WIMPs Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  7. Why a Linear Collider? Key features of the e +e-( and γe, γ γ) collider: • Precisely defined and known cms energy of hard process (machine requirements: low beam energy spread, low beamstrahlung) • Tunablecms energy (machine requirements: flexibility, high luminosity) • Polarized initial beams (machine and detector requirements: • Clean and fully reconstructable events (hadronic, invisible) (detector requirements: jet, lepton reconstruction, full hermiticity) • Moderate backgrounds: no trigger required! rather unbiased physics…. Large potential for direct discoveries and via high precision ! Pre-SUSY, Bonn, 19-21.8.2010 GudridMoortgat-Pick

  8. 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. t Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  9. At the precision frontier: the LC ICFA Parameter Group Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  10. Synergy effects: LHC2FC@CERN 2/09 Questions from early LHC data ( ~10 fb-1 ) • ‘Famous’ 3 cases (cf. CERN strategy documents) : • LHC not detected anything • LHC only detected SM-like Higgs • LHC detected some new physics • What could the LC do • in first ILC stage of 90 up to 500 GeV? • in LC upgrades? • in multi-TeV CLIC option? Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  11. Nothing found at (early) LHC • Interpretation for ILC? • ‘Top’ physics • indirect searches in bb, cc, l l ( large ED, CI) • ew precision runs from Z-pole data • But is then really 500 GeV as first ILC stage needed? • or better 350 GeV? High-lumi Z-factory? Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  12. Physics up to sqrt(s)=500 GeV: top mtop= 173.3 +- 1.1 GeV Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  13. Top mass • From running at tt threshold: • Measurement of a ‘threshold • mass parameter’’ with high • precision: < 20 MeV • +transition to suitably defined • (short-distance) top-quark • mass, e.g. MS mass • We expect at the LC: • δmtexp<100 MeV (dominated by theory uncertainty) Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  14. Importance of ‘top’ mass Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  15. EW precision measurements • GigaZ option at the ILC: • high-lumi running on Z-pole/WW • 109 Z in 50-100 days of running • Needs machine changes (bypass in the current outline) • High precision needs polarized beams • Provides measurement of sin2θW with unprecedented precision! Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  16. Electroweak precision data Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  17. Measuring the ew mixing angle • Measuring the AFB , ALR can be interpreted as measuring sin2θW • LEP result: sin2θW=0.23221±0.00029 • SLC result: sin2θW=0.23098±0.00026 • Discrepancy between AFB and ALR -> impact on Higgs tests ! Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  18. mW vs. central value sin2θeff → Consistent with SM and SUSY Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  19. mW vs. SLD-value sin2θeff → not consistent with the SM Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  20. mW vs. LEP -value sin2θeff → not consistent with neither SM nor SUSY Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  21. Blondel scheme for GigaZ Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  22. Relevance in worst case scenarios • Hints for new physics in worst case scenarios: • Only Higgs @LHC • No hints for SUSY • Deviations at Zpole • Hints for SUSY • Discrepancy Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  23. SUSY Constraints from GigaZ Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  24. What’s needed? ….polarized beams e+ polarization is an absolute novelty! Expected P(e+) ~ 60% Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  25. Polarized positrons Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  26. Polarized cross sections in general Polarized cross sections can be subdivided in: σRR, σLL, σRL, σLR are contributions with fully polarized L, R beams. In case of a vector particle only (LR) and (RL) configurations contribute: Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  27. Effective polarization • Effective polarization: Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  28. Relation between Peff and ALR How are Peff and ALR related? That means: With pure error propagation (and errors uncorrelated), one obtains: With Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  29. Gain in accuracy due to P(e+) Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  30. Only SM-like Higgs at early LHC • Interpretation for ILC • best-suited for studying Higgs properties • precise determination of couplings: determination of Hbb is crucial! • distinction: SM- versus SUSY Higgs • t t H and trilinear Higgs coup. challenging • But is then really 500 GeV as 1st step needed? • Optimize running scenarios (tunable energy, polarization) Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  31. Determination of Higgs properties • Higgs spin LHC input for optimal choices of running scenarios ! Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  32. Higgs physics at ILC • Higgs Strahlung WW fusion Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  33. Higgs mass • Use Higgsstrahlung: due to well-known initial state and well-observed Z-decays • Derive Higgs mass independently from decay ! • Only possible at a LC! Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  34. Higgs properties Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  35. Something ‘new’ detected at early LHC • SUSY-like signals (many tics at big questions!) • At least partial spectrum accessible at ILC • ‘light’ SUSY consis- tent with precision fits • Extra gauge bosons and/or large extra dimensions (some tics at big questions!) • High precision in indirect searches allow model distinction and couplings determination Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  36. 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 • Unraveling 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! Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  37. Discovery of SUSY Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  38. SUSY mass measurement im continuum Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  39. Masses and spin via threshold scans • Assume LHC provides mass of a SUSY particle: Pre-SUSY, Bonn, 19-21.8.2010 GudridMoortgat-Pick

  40. Mass measurement of the LSP mass Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  41. Properties of WIMP’s: mass+spin • Reconstruct the `invisible’: • via recoil mass distribution Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  42. Verify SUSY properties at ILC Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  43. Slepton `chiral’ quantum numbers Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  44. Sensitivity to heavy SUSY particles • Challenging scenarios: • multi-TeV sfermions, only few light gauginos (‘focuspoint-like’) also very difficult for LHC … • sensitivity to heavy sneutrinos in t-channel Suitable observable: Precise measurement of asymmetry copes with multi-TeV particles ! Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  45. Free parameters in the MSSM Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  46. SUSY parameter determination • Exploit just light SUSY particle spectrum at ILC and • determine the parameters (see below) • Combine it with LHC results via prediction of heavier states Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  47. SUSY multi-parameter fits: LHC Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  48. SUSY multi parameter fits: LHC+ILC Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  49. Aside: Disney World of SUSY scenarios • Often (ab)used plots: • 13 SUSY ‘benchmarks’ scenarios out of millions … • really a true representative choice ? Consistent with current bounds? • heavy masses often mass degenerated: no resolution • (beamstrahlung!) has been taken into account… • really a reliable ‘counting’ ? • experimental verification of properties not studied … • really a useful basis for future decisions? • Pure particle counting as justification of the energy scale • -but what’s about the achievable precision? • -but what can be learned via precisions observables at • lower energies? (GigaZ, AFB,…) • General feature: in order to be consistent with existing experimental bounds, e.g. with gμ-2: • a few gauginos have to be rather light ! ….sufficient as 1.step Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

  50. Indirect searches: extra dimensions Pre-SUSY, Bonn, 19-21.8.2010 Gudrid Moortgat-Pick

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