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James Stirling IPPP, University of Durham

The International Linear Collider – an overview of the physics motivation and theory. James Stirling IPPP, University of Durham with acknowledgements to R Barbieri, J Ellis, D Miller (ICHEP04), M Peskin (Victoria LCW), S. Dawson, R. Heuer. the most up-to-date reference….

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James Stirling IPPP, University of Durham

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  1. The International Linear Collider – an overview of the physics motivation and theory James Stirling IPPP, University of Durham with acknowledgements to R Barbieri, J Ellis, D Miller (ICHEP04), M Peskin (Victoria LCW), S. Dawson, R. Heuer

  2. the most up-to-date reference… The LHC-LC Study Group Report Georg Weiglein et al. www.ippp.dur.ac.uk/~georg/lhclc/ ECFA Workshop

  3. gauge sector flavour sector EWSB sector  mass sector Particle Physics 2004 … and beyond? ECFA Workshop

  4. QCD 1  mass ? QCD 2 gauge sector CKM flavour sector EWSB sector pentaquarks  mass sector EWSB Particle Physics 2004 … and beyond? ECFA Workshop

  5. ? 2.7 NuTeV g-2 LEPEWWG 2004 discrepancies? ECFA Workshop

  6. Higgs SUSY dark matter limits? ECFA Workshop

  7. particle physics the key questions • What is the origin of mass? Is it the Higgs mechanism or …? • What is the origin of the matter-antimatter asymmetry in the universe? • What are the properties of neutrinos? • Is there unification of particles and forces including gravity? • What is the dark matter? 2)  present and future B Factories 3)  solar, atmospheric, reactor, (super)beam, 0, …, NuFact experiments 1), 4), 5)  high-energy colliders: Tevatron, LHC, ILC ECFA Workshop

  8. + gauge unification • + dark matter candidate • + ‘naturally’ consistent with PEW data • but… • where is the Higgs? • where are the superpartners? • “little hierarchy” problem! • then… • NMSSM with heavier h0 , more neutral scalars etc. • Little Higgs Models • embed SM in large gauge group • Higgs as PGB • in mh2 cancel top loop with new heavy T quark • new quarks, gauge bosons, Higgs bosons in • the 1 – 10 TeV range • but… • too many such models? • too ad hoc? • nevertheless… • at the very least, a useful “straw-man” alternative to SUSY! key issue: electroweak symmetry breaking Scenarios include: • Supersymmetry (MSSM and variants) • Higgs as Pseudo Goldstone Boson • Composite Higgs • Technicolour • Higgsless models • Extra dimensions • … Note: in all scenarios, something (or some combination of things) has to mimic a light Higgs boson in the precision electroweak (EWPO) fits! TheCalculability Principle(Barbieri): Restrict to models in which the Fermi scale (GF-1 or MZ) can be related to some other physical scale (NP say) in a calculable manner, i.e. MZ =NPf(ai) where the ai are physical parameters. Then CP  consistency with data  SUSY, Higgs as PGB ECFA Workshop

  9. fb-1 1 year @1034 1 year @1033 1 month @1033 LHC: ATLAS what LHC can do: SM-like Higgs ECFA Workshop

  10. what LHC can do: SUSY Higgses sparticles  whole plane covered for at least one Higgs (but note large “only h” region!)  squark and gluino masses eventually up to ~2.5 TeV ECFA Workshop

  11. however… • ‘hadro-philic’ bias in new physics searches (gg,qq  X) • large SM backgrounds always a problem (Higgs< total  10-9) • EWPO: only modest improvement over Tevatron (mtop ,mW ) • no longitudinal momentum balance; ‘missing pT’ for invisible particles is relatively crude tool; quark flavour tagging difficult • strong model dependence of new physics analyses: conventional SUSY neutrino LSP (Murayama et al) ‘bosonic supersymmetry’ (Cheng, Matchev, Schmaltz) multiple hypotheses, distinguished by different spin and energy flows, difficult to distinguish at LHC Peskin (Victoria, 2004) ECFA Workshop

  12. cross sections: LHC vs. ILC ECFA Workshop

  13. ILC physics summary whatever the scenario unveiled by Tevatron & LHC, ILC has an essential role to play • continue with precision electroweak measurements (in particular, mtop ) • if a light Higgs exists, measure its properties (mass, couplings to fermions & gauge bosons, self-couplings, …) • if LHC reveals other light ( e.g. SUSY) particles, measure the spectrum and properties • if LHC reveals no light particles, explore the ~1 TeV region through precision measurements sensitive to virtual new physics ECFA Workshop

  14. t W b + H current MW + … precision MW = cosw MZ  [ 1 + α F(mt,MH,SUSY,..)+ …] Heinemeyer et al (LHCLC report) Heinemeyer, Weiglein 04

  15. precision contd. precision EW measurements complement direct new physics measurements Heinemeyer et al 2003 ECFA Workshop

  16. Higgs physics at ILC • Key questions • precise mass? • couplings to other particles – SM or not? • self-couplings? • other higgses? ECFA Workshop

  17. Higgs physics at ILC • Key questions • precise mass? • couplings to other particles – SM or not? • self-couplings? • other higgses? with compare Guasch, Hollik, Penaranda 2003 Example: also ttH coupling measurements – see LHCLC report

  18. Z e Z* h e h Higgs physics at ILC • Key questions • precise mass? • couplings to other particles – SM or not? • self-couplings? • other Higgses? V() = ½ mh22 + 3v 3 + ¼ 44 in SM:3 = 4=½ mh2 v-2 3 / 3~ 20% ECFA Workshop

  19. supersymmetry at the ILC the task: • determination of kinematically accessible sparticle spectrum • measure sparticle properties (masses, cross sections, JPC) • use these (with complementary information from LHC) to constrain underlying SUSY model • extrapolate to GUT scale using RGEs the techniques: • end point spectra • threshold scans • +e-e-, e, polarised beams ECFA Workshop

  20. example of a global MSSM spectrum fit * * * + LSP * * + * * - - + + + * Needs > 500 GeV. (Also<500 study in LHC/LC) + e+e- threshold scan. - e-e- threshold scan (s-wave allowed) David Miller, ICHEP04

  21. the LHC-LC synergy: using precisely measured LSP mass at ILC to constrain LHC measurements of slepton and squark masses see e.g. LHCLC report for details, many more examples, and references

  22. … then on to the GUT scale! Allanach, Blair, Kraml, Martyn, Polesello, Porod,,Zerwas ECFA Workshop

  23. t W b + h W + ? f e e Z’ Z’  WL e e e f W e WL  … and if nothing below 500 GeV? a generic feature of such models is heavy s-channel resonances in the 1-3 TeV range (new gauge bosons, technipions, KK resonances, …) little Higgs heavy Higgs no Higgs … ECFA Workshop

  24. ILC (eeff) LHC (direct) assume a1=1 sensitivity to new heavy resonances in ee WW sensitivity to new heavy Z’ LC LHC M = 1.9 TeV SM couplings (a=1) LC: 500 GeV, 500 pb-1 Richard 2003 Barklow et al, LHCLC report ECFA Workshop

  25. ILClooks beyond LHC’s direct reach Then LHC + ILC point to CLIC, and maybe superLHC David Miller ICHEP04 Summary of the case for the TeV ILC 1. Definite; mt<100MeV • If LHC sees nothing new • below ~ 500 GeV mass Vital constraint. Increasingly sure it can be done. 2. If there is a light Higgs LHC probably sees. ILCshows what it is. LHC and ILC needed to pin down model, identify DM(?), extrapolate to GUT scale. 3. and extra particles

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