1. 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 International Linear Collider – an overview of the physics motivation and theory

2. WJ Stirling ECFA Workshop2 the most up-to-date reference… The LHC-LC Study Group Report Georg Weiglein et al. www.ippp.dur.ac.uk/~georg/lhclc/

3. WJ Stirling ECFA Workshop3 Particle Physics 2004 gauge sector mass sector EWSB sectorflavour sector … and beyond?

4. WJ Stirling ECFA Workshop4 Particle Physics 2004 gauge sector mass sector EWSB sectorflavour sector … and beyond? QCD 1 ? pentaquarks QCD 2 CKM EWSB mass

5. WJ Stirling ECFA Workshop5 2.7  g-2 discrepancies? NuTeV LEPEWWG 2004 ?

6. WJ Stirling ECFA Workshop6 limits? Higgs SUSY dark matter

7. WJ Stirling ECFA Workshop7 the key questions 1) What is the origin of mass? Is it the Higgs mechanism or …? 2) What is the origin of the matter-antimatter asymmetry in the universe? 3) What are the properties of neutrinos? 4) Is there unification of particles and forces including gravity? 5) What is the dark matter? particle physics 2)  present and future B Factories 3)  solar, atmospheric, reactor, (super)beam, 0 , …, NuFact experiments 1), 4), 5)  high-energy colliders: Tevatron, LHC, ILC

8. WJ Stirling ECFA Workshop8 key issue: electroweak symmetry breaking 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! Scenarios include: The Calculability Principle (Barbieri): Restrict to models in which the Fermi scale (G F -1 or M Z ) can be related to some other physical scale (  NP say) in a calculable manner, i.e. M Z =  NP f(a i ) where the a i are physical parameters. Then CP  consistency with data  SUSY, Higgs as PGB + 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 h 0, more neutral scalars etc. Little Higgs Models embed SM in large gauge group Higgs as PGB in  m h 2 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!

9. WJ Stirling ECFA Workshop9 what LHC can do: SM-like Higgs fb -1 LHC: ATLAS 1 year @10 33 1 year @10 34 1 month @10 33

10. WJ Stirling ECFA Workshop10 what LHC can do: SUSY Higgsessparticles  whole plane covered for at least one Higgs (but note large “only h” region!)  squark and gluino masses eventually up to ~2.5 TeV

11. WJ Stirling ECFA Workshop11 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 ( m top, m W ) no longitudinal momentum balance; ‘missing p T ’ 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)

12. WJ Stirling ECFA Workshop12 cross sections: LHC vs. ILC

13. WJ Stirling ECFA Workshop13 ILC physics summary whatever the scenario unveiled by Tevatron & LHC, ILC has an essential role to play continue with precision electroweak measurements (in particular, m top ) 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

14. precision current  M W Heinemeyer et al (LHCLC report)  m W (MeV)  m top (GeV)  sin 2  eff  10 5 now343.917 TeV Run 2161.429 LHC151-214-20 ILC-GigaZ70.11.3 M W = cos  w M Z  [ 1 + α F(m t,M H,SUSY,..)+ … ] W H b + t + … Heinemeyer, Weiglein 04

15. WJ Stirling ECFA Workshop15 precision contd. Heinemeyer et al 2003 precision EW measurements complement direct new physics measurements

16. WJ Stirling ECFA Workshop16 Key questions precise mass? couplings to other particles – SM or not? self-couplings? other higgses? Higgs physics at ILC

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

18. WJ Stirling ECFA Workshop18 Key questions precise mass? couplings to other particles – SM or not? self-couplings? other Higgses? Higgs physics at ILC V(  ) = ½ m h 2  2 + 3 v  3 + ¼ 4  4 in SM: 3 = 4 = ½ m h 2 v -2  3 / 3 ~ 20% h h Z* e e Z

19. WJ Stirling ECFA Workshop19 supersymmetry at the ILC the task: determination of kinematically accessible sparticle spectrum measure sparticle properties (masses, cross sections, J PC ) 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

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

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

22. WJ Stirling ECFA Workshop22 … then on to the GUT scale! Allanach, Blair, Kraml, Martyn, Polesello, Porod,,Zerwas

23. WJ Stirling ECFA Workshop23 … and if nothing below 500 GeV? W h b + t +? little Higgs heavy Higgs no Higgs … a generic feature of such models is heavy s- channel resonances in the 1-3 TeV range (new gauge bosons, technipions, KK resonances, …) e e W W Z’ e e f f e e WLWL WLWL

24. WJ Stirling ECFA Workshop24 ILC (ee  ff) LHC (direct) sensitivity to new heavy Z’ sensitivity to new heavy resonances in ee  WW M = 1.9 TeV SM couplings (a=1) LC: 500 GeV, 500 pb -1 LHC LC assume a 1 =1 Richard 2003 Barklow et al, LHCLC report

25. Summary of the case for the TeV ILC 1. Definite;  m t <100MeV 2. If there is a light Higgs 3. and extra particles 4.If LHC sees nothing new below ~ 500 GeV mass Vital constraint. Increasingly sure it can be done. LHC probably sees. ILC shows what it is. LHC and ILC needed to pin down model, identify DM(?), extrapolate to GUT scale. Then LHC + ILC point to CLIC, and maybe superLHC ILC looks beyond LHC’s direct reach David Miller ICHEP04